FFV1 Video Coding Format Version 0, 1, and 3
draft-ietf-cellar-ffv1-10

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cellar                                                    M. Niedermayer
Internet-Draft                                                   D. Rice
Intended status: Informational                               J. Martinez
Expires: 12 April 2020                                   10 October 2019

              FFV1 Video Coding Format Version 0, 1, and 3
                       draft-ietf-cellar-ffv1-10

Abstract

   This document defines FFV1, a lossless intra-frame video encoding
   format.  FFV1 is designed to efficiently compress video data in a
   variety of pixel formats.  Compared to uncompressed video, FFV1
   offers storage compression, frame fixity, and self-description, which
   makes FFV1 useful as a preservation or intermediate video format.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 12 April 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   4
     2.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   5
       2.2.1.  Pseudo-code . . . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  Arithmetic Operators  . . . . . . . . . . . . . . . .   6
       2.2.3.  Assignment Operators  . . . . . . . . . . . . . . . .   6
       2.2.4.  Comparison Operators  . . . . . . . . . . . . . . . .   7
       2.2.5.  Mathematical Functions  . . . . . . . . . . . . . . .   7
       2.2.6.  Order of Operation Precedence . . . . . . . . . . . .   8
       2.2.7.  Range . . . . . . . . . . . . . . . . . . . . . . . .   8
       2.2.8.  NumBytes  . . . . . . . . . . . . . . . . . . . . . .   8
       2.2.9.  Bitstream Functions . . . . . . . . . . . . . . . . .   8
   3.  Sample Coding . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Border  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.2.  Samples . . . . . . . . . . . . . . . . . . . . . . . . .  10
     3.3.  Median Predictor  . . . . . . . . . . . . . . . . . . . .  10
     3.4.  Context . . . . . . . . . . . . . . . . . . . . . . . . .  11
     3.5.  Quantization Table Sets . . . . . . . . . . . . . . . . .  12
     3.6.  Quantization Table Set Indexes  . . . . . . . . . . . . .  12
     3.7.  Color spaces  . . . . . . . . . . . . . . . . . . . . . .  12
       3.7.1.  YCbCr . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.7.2.  RGB . . . . . . . . . . . . . . . . . . . . . . . . .  13
     3.8.  Coding of the Sample Difference . . . . . . . . . . . . .  15
       3.8.1.  Range Coding Mode . . . . . . . . . . . . . . . . . .  15
       3.8.2.  Golomb Rice Mode  . . . . . . . . . . . . . . . . . .  20
   4.  Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . .  25
     4.1.  Parameters  . . . . . . . . . . . . . . . . . . . . . . .  26
       4.1.1.  version . . . . . . . . . . . . . . . . . . . . . . .  28
       4.1.2.  micro_version . . . . . . . . . . . . . . . . . . . .  28
       4.1.3.  coder_type  . . . . . . . . . . . . . . . . . . . . .  29
       4.1.4.  state_transition_delta  . . . . . . . . . . . . . . .  29
       4.1.5.  colorspace_type . . . . . . . . . . . . . . . . . . .  29
       4.1.6.  chroma_planes . . . . . . . . . . . . . . . . . . . .  30
       4.1.7.  bits_per_raw_sample . . . . . . . . . . . . . . . . .  30
       4.1.8.  log2_h_chroma_subsample . . . . . . . . . . . . . . .  31
       4.1.9.  log2_v_chroma_subsample . . . . . . . . . . . . . . .  31
       4.1.10. extra_plane . . . . . . . . . . . . . . . . . . . . .  31
       4.1.11. num_h_slices  . . . . . . . . . . . . . . . . . . . .  31
       4.1.12. num_v_slices  . . . . . . . . . . . . . . . . . . . .  32
       4.1.13. quant_table_set_count . . . . . . . . . . . . . . . .  32
       4.1.14. states_coded  . . . . . . . . . . . . . . . . . . . .  32
       4.1.15. initial_state_delta . . . . . . . . . . . . . . . . .  32
       4.1.16. ec  . . . . . . . . . . . . . . . . . . . . . . . . .  33
       4.1.17. intra . . . . . . . . . . . . . . . . . . . . . . . .  33
     4.2.  Configuration Record  . . . . . . . . . . . . . . . . . .  33

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       4.2.1.  reserved_for_future_use . . . . . . . . . . . . . . .  34
       4.2.2.  configuration_record_crc_parity . . . . . . . . . . .  34
       4.2.3.  Mapping FFV1 into Containers  . . . . . . . . . . . .  34
     4.3.  Frame . . . . . . . . . . . . . . . . . . . . . . . . . .  35
     4.4.  Slice . . . . . . . . . . . . . . . . . . . . . . . . . .  37
     4.5.  Slice Header  . . . . . . . . . . . . . . . . . . . . . .  38
       4.5.1.  slice_x . . . . . . . . . . . . . . . . . . . . . . .  38
       4.5.2.  slice_y . . . . . . . . . . . . . . . . . . . . . . .  38
       4.5.3.  slice_width . . . . . . . . . . . . . . . . . . . . .  38
       4.5.4.  slice_height  . . . . . . . . . . . . . . . . . . . .  39
       4.5.5.  quant_table_set_index_count . . . . . . . . . . . . .  39
       4.5.6.  quant_table_set_index . . . . . . . . . . . . . . . .  39
       4.5.7.  picture_structure . . . . . . . . . . . . . . . . . .  39
       4.5.8.  sar_num . . . . . . . . . . . . . . . . . . . . . . .  39
       4.5.9.  sar_den . . . . . . . . . . . . . . . . . . . . . . .  40
     4.6.  Slice Content . . . . . . . . . . . . . . . . . . . . . .  40
       4.6.1.  primary_color_count . . . . . . . . . . . . . . . . .  41
       4.6.2.  plane_pixel_height  . . . . . . . . . . . . . . . . .  41
       4.6.3.  slice_pixel_height  . . . . . . . . . . . . . . . . .  41
       4.6.4.  slice_pixel_y . . . . . . . . . . . . . . . . . . . .  41
     4.7.  Line  . . . . . . . . . . . . . . . . . . . . . . . . . .  41
       4.7.1.  plane_pixel_width . . . . . . . . . . . . . . . . . .  42
       4.7.2.  slice_pixel_width . . . . . . . . . . . . . . . . . .  42
       4.7.3.  slice_pixel_x . . . . . . . . . . . . . . . . . . . .  42
       4.7.4.  sample_difference . . . . . . . . . . . . . . . . . .  42
     4.8.  Slice Footer  . . . . . . . . . . . . . . . . . . . . . .  43
       4.8.1.  slice_size  . . . . . . . . . . . . . . . . . . . . .  43
       4.8.2.  error_status  . . . . . . . . . . . . . . . . . . . .  43
       4.8.3.  slice_crc_parity  . . . . . . . . . . . . . . . . . .  43
     4.9.  Quantization Table Set  . . . . . . . . . . . . . . . . .  44
       4.9.1.  quant_tables  . . . . . . . . . . . . . . . . . . . .  45
       4.9.2.  context_count . . . . . . . . . . . . . . . . . . . .  45
   5.  Restrictions  . . . . . . . . . . . . . . . . . . . . . . . .  45
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  46
   7.  Media Type Definition . . . . . . . . . . . . . . . . . . . .  47
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  48
   9.  Appendixes  . . . . . . . . . . . . . . . . . . . . . . . . .  48
     9.1.  Decoder implementation suggestions  . . . . . . . . . . .  48
       9.1.1.  Multi-threading Support and Independence of
               Slices  . . . . . . . . . . . . . . . . . . . . . . .  48
   10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  49
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  49
   12. Informative References  . . . . . . . . . . . . . . . . . . .  50
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  51

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1.  Introduction

   This document describes FFV1, a lossless video encoding format.  The
   design of FFV1 considers the storage of image characteristics, data
   fixity, and the optimized use of encoding time and storage
   requirements.  FFV1 is designed to support a wide range of lossless
   video applications such as long-term audiovisual preservation,
   scientific imaging, screen recording, and other video encoding
   scenarios that seek to avoid the generational loss of lossy video
   encodings.

   This document defines version 0, 1 and 3 of FFV1.  The distinctions
   of the versions are provided throughout the document, but in summary:

   *  Version 0 of FFV1 was the original implementation of FFV1 and has
      been in non-experimental use since April 14, 2006 [FFV1_V0].

   *  Version 1 of FFV1 adds support of more video bit depths and has
      been in use since April 24, 2009 [FFV1_V1].

   *  Version 2 of FFV1 only existed in experimental form and is not
      described by this document, but is available as a LyX file at
      https://github.com/FFmpeg/FFV1/
      blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx
      (https://github.com/FFmpeg/FFV1/
      blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx).

   *  Version 3 of FFV1 adds several features such as increased
      description of the characteristics of the encoding images and
      embedded CRC data to support fixity verification of the encoding.
      Version 3 has been in non-experimental use since August 17, 2013
      [FFV1_V3].

   The latest version of this document is available at
   https://raw.github.com/FFmpeg/FFV1/master/ffv1.md
   (https://raw.github.com/FFmpeg/FFV1/master/ffv1.md)

   This document assumes familiarity with mathematical and coding
   concepts such as Range coding [range-coding] and YCbCr color spaces
   [YCbCr].

2.  Notation and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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2.1.  Definitions

   "Container": Format that encapsulates "Frames" (see the section on
   Frames (#frame)) and (when required) a "Configuration Record" into a
   bitstream.

   "Sample": The smallest addressable representation of a color
   component or a luma component in a "Frame".  Examples of "Sample" are
   Luma, Blue Chrominance, Red Chrominance, Transparency, Red, Green,
   and Blue.

   "Plane": A discrete component of a static image comprised of
   "Samples" that represent a specific quantification of "Samples" of
   that image.

   "Pixel": The smallest addressable representation of a color in a
   "Frame".  It is composed of 1 or more "Samples".

   "ESC": An ESCape symbol to indicate that the symbol to be stored is
   too large for normal storage and that an alternate storage method is
   used.

   "MSB": Most Significant Bit, the bit that can cause the largest
   change in magnitude of the symbol.

   "RCT": Reversible Color Transform, a near linear, exactly reversible
   integer transform that converts between RGB and YCbCr representations
   of a "Pixel".

   "VLC": Variable Length Code, a code that maps source symbols to a
   variable number of bits.

   "RGB": A reference to the method of storing the value of a "Pixel" by
   using three numeric values that represent Red, Green, and Blue.

   "YCbCr": A reference to the method of storing the value of a "Pixel"
   by using three numeric values that represent the luma of the "Pixel"
   (Y) and the chrominance of the "Pixel" (Cb and Cr).  YCbCr word is
   used for historical reasons and currently references any color space
   relying on 1 luma "Sample" and 2 chrominance "Samples", e.g.  YCbCr,
   YCgCo or ICtCp.  The exact meaning of the three numeric values is
   unspecified.

   "TBA": To Be Announced.  Used in reference to the development of
   future iterations of the FFV1 specification.

2.2.  Conventions

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2.2.1.  Pseudo-code

   The FFV1 bitstream is described in this document using pseudo-code.
   Note that the pseudo-code is used for clarity in order to illustrate
   the structure of FFV1 and not intended to specify any particular
   implementation.  The pseudo-code used is based upon the C programming
   language [ISO.9899.1990] and uses its "if/else", "while" and "for"
   functions as well as functions defined within this document.

2.2.2.  Arithmetic Operators

   Note: the operators and the order of precedence are the same as used
   in the C programming language [ISO.9899.1990].

   "a + b" means a plus b.

   "a - b" means a minus b.

   "-a" means negation of a.

   "a * b" means a multiplied by b.

   "a / b" means a divided by b.

   "a ^ b" means a raised to the b-th power.

   "a & b" means bit-wise "and" of a and b.

   "a | b" means bit-wise "or" of a and b.

   "a >> b" means arithmetic right shift of two's complement integer
   representation of a by b binary digits.

   "a << b" means arithmetic left shift of two's complement integer
   representation of a by b binary digits.

2.2.3.  Assignment Operators

   "a = b" means a is assigned b.

   "a++" is equivalent to a is assigned a + 1.

   "a--" is equivalent to a is assigned a - 1.

   "a += b" is equivalent to a is assigned a + b.

   "a -= b" is equivalent to a is assigned a - b.

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   "a *= b" is equivalent to a is assigned a * b.

2.2.4.  Comparison Operators

   "a > b" means a is greater than b.

   "a >= b" means a is greater than or equal to b.

   "a < b" means a is less than b.

   "a <= b" means a is less than or equal b.

   "a == b" means a is equal to b.

   "a != b" means a is not equal to b.

   "a && b" means Boolean logical "and" of a and b.

   "a || b" means Boolean logical "or" of a and b.

   "!a" means Boolean logical "not" of a.

   "a ? b : c" if a is true, then b, otherwise c.

2.2.5.  Mathematical Functions

   floor(a) the largest integer less than or equal to a

   ceil(a) the smallest integer greater than or equal to a

   sign(a) extracts the sign of a number, i.e. if a < 0 then -1, else if
   a > 0 then 1, else 0

   abs(a) the absolute value of a, i.e. abs(a) = sign(a)*a

   log2(a) the base-two logarithm of a

   min(a,b) the smallest of two values a and b

   max(a,b) the largest of two values a and b

   median(a,b,c) the numerical middle value in a data set of a, b, and
   c, i.e. a+b+c-min(a,b,c)-max(a,b,c)

   a_(b) the b-th value of a sequence of a

   a~b,c.  the 'b,c'-th value of a sequence of a

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2.2.6.  Order of Operation Precedence

   When order of precedence is not indicated explicitly by use of
   parentheses, operations are evaluated in the following order (from
   top to bottom, operations of same precedence being evaluated from
   left to right).  This order of operations is based on the order of
   operations used in Standard C.

   a++, a--
   !a, -a
   a ^ b
   a * b, a / b, a % b
   a + b, a - b
   a << b, a >> b
   a < b, a <= b, a > b, a >= b
   a == b, a != b
   a & b
   a | b
   a && b
   a || b
   a ? b : c
   a = b, a += b, a -= b, a *= b

2.2.7.  Range

   "a...b" means any value starting from a to b, inclusive.

2.2.8.  NumBytes

   "NumBytes" is a non-negative integer that expresses the size in 8-bit
   octets of a particular FFV1 "Configuration Record" or "Frame".  FFV1
   relies on its "Container" to store the "NumBytes" values, see the
   section on the Mapping FFV1 into Containers (#mapping-ffv1-into-
   containers).

2.2.9.  Bitstream Functions

2.2.9.1.  remaining_bits_in_bitstream

   "remaining_bits_in_bitstream( )" means the count of remaining bits
   after the pointer in that "Configuration Record" or "Frame".  It is
   computed from the "NumBytes" value multiplied by 8 minus the count of
   bits of that "Configuration Record" or "Frame" already read by the
   bitstream parser.

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2.2.9.2.  remaining_symbols_in_syntax

   "remaining_symbols_in_syntax( )" is true as long as the RangeCoder
   has not consumed all the given input bytes.

2.2.9.3.  byte_aligned

   "byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes
   )" is a multiple of 8, otherwise false.

2.2.9.4.  get_bits

   "get_bits( i )" is the action to read the next "i" bits in the
   bitstream, from most significant bit to least significant bit, and to
   return the corresponding value.  The pointer is increased by "i".

3.  Sample Coding

   For each "Slice" (as described in the section on Slices (#slice)) of
   a "Frame", the "Planes", "Lines", and "Samples" are coded in an order
   determined by the "Color Space" (see the section on Color Space
   (#color-spaces)).  Each "Sample" is predicted by the median predictor
   as described in the section of the Median Predictor (#median-
   predictor) from other "Samples" within the same "Plane" and the
   difference is stored using the method described in Coding of the
   Sample Difference (#coding-of-the-sample-difference).

3.1.  Border

   A border is assumed for each coded "Slice" for the purpose of the
   median predictor and context according to the following rules:

   *  one column of "Samples" to the left of the coded slice is assumed
      as identical to the "Samples" of the leftmost column of the coded
      slice shifted down by one row.  The value of the topmost "Sample"
      of the column of "Samples" to the left of the coded slice is
      assumed to be "0"

   *  one column of "Samples" to the right of the coded slice is assumed
      as identical to the "Samples" of the rightmost column of the coded
      slice

   *  an additional column of "Samples" to the left of the coded slice
      and two rows of "Samples" above the coded slice are assumed to be
      "0"

   The following table depicts a slice of 9 "Samples"

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   "a,b,c,d,e,f,g,h,i" in a 3x3 arrangement along with its assumed
   border.

   +---+---+---+---+---+---+---+---+
   | 0 | 0 |   | 0 | 0 | 0 |   | 0 |
   +---+---+---+---+---+---+---+---+
   | 0 | 0 |   | 0 | 0 | 0 |   | 0 |
   +---+---+---+---+---+---+---+---+
   |   |   |   |   |   |   |   |   |
   +---+---+---+---+---+---+---+---+
   | 0 | 0 |   | a | b | c |   | c |
   +---+---+---+---+---+---+---+---+
   | 0 | a |   | d | e | f |   | f |
   +---+---+---+---+---+---+---+---+
   | 0 | d |   | g | h | i |   | i |
   +---+---+---+---+---+---+---+---+

3.2.  Samples

   Relative to any "Sample" "X", six other relatively positioned
   "Samples" from the coded "Samples" and presumed border are identified
   according to the labels used in the following diagram.  The labels
   for these relatively positioned "Samples" are used within the median
   predictor and context.

   +---+---+---+---+
   |   |   | T |   |
   +---+---+---+---+
   |   |tl | t |tr |
   +---+---+---+---+
   | L | l | X |   |
   +---+---+---+---+

   The labels for these relative "Samples" are made of the first letters
   of the words Top, Left and Right.

3.3.  Median Predictor

   The prediction for any "Sample" value at position "X" may be computed
   based upon the relative neighboring values of "l", "t", and "tl" via
   this equation:

   "median(l, t, l + t - tl)".

   Note, this prediction template is also used in [ISO.14495-1.1999] and
   [HuffYUV].

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   Exception for the median predictor: if "colorspace_type == 0 &&
   bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )",
   the following median predictor MUST be used:

   "median(left16s, top16s, left16s + top16s - diag16s)"

   where:

   left16s = l  >= 32768 ? ( l  - 65536 ) : l
   top16s  = t  >= 32768 ? ( t  - 65536 ) : t
   diag16s = tl >= 32768 ? ( tl - 65536 ) : tl

   Background: a two's complement signed 16-bit signed integer was used
   for storing "Sample" values in all known implementations of FFV1
   bitstream.  So in some circumstances, the most significant bit was
   wrongly interpreted (used as a sign bit instead of the 16th bit of an
   unsigned integer).  Note that when the issue is discovered, the only
   configuration of all known implementations being impacted is 16-bit
   YCbCr with no Pixel transformation with Range Coder coder, as other
   potentially impacted configurations (e.g. 15/16-bit JPEG2000-RCT with
   Range Coder coder, or 16-bit content with Golomb Rice coder) were
   implemented nowhere [ISO.15444-1.2016].  In the meanwhile, 16-bit
   JPEG2000-RCT with Range Coder coder was implemented without this
   issue in one implementation and validated by one conformance checker.
   It is expected (to be confirmed) to remove this exception for the
   median predictor in the next version of the FFV1 bitstream.

3.4.  Context

   Relative to any "Sample" "X", the Quantized Sample Differences "L-l",
   "l-tl", "tl-t", "T-t", and "t-tr" are used as context:

   context = Q_{0}[l - tl] +
             Q_{1}[tl - t] +
             Q_{2}[t - tr] +
             Q_{3}[L - l]  +
             Q_{4}[T - t]

                                  Figure 1

   If "context >= 0" then "context" is used and the difference between
   the "Sample" and its predicted value is encoded as is, else
   "-context" is used and the difference between the "Sample" and its
   predicted value is encoded with a flipped sign.

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3.5.  Quantization Table Sets

   The FFV1 bitstream contains 1 or more Quantization Table Sets.  Each
   Quantization Table Set contains exactly 5 Quantization Tables with
   each Quantization Table corresponding to 1 of the 5 Quantized Sample
   Differences.  For each Quantization Table, both the number of
   quantization steps and their distribution are stored in the FFV1
   bitstream; each Quantization Table has exactly 256 entries, and the 8
   least significant bits of the Quantized Sample Difference are used as
   index:

   Q_{j}[k] = quant_tables[i][j][k&255]

                                  Figure 2

   In this formula, "i" is the Quantization Table Set index, "j" is the
   Quantized Table index, "k" the Quantized Sample Difference.

3.6.  Quantization Table Set Indexes

   For each "Plane" of each slice, a Quantization Table Set is selected
   from an index:

   *  For Y "Plane", "quant_table_set_index[ 0 ]" index is used

   *  For Cb and Cr "Planes", "quant_table_set_index[ 1 ]" index is used

   *  For extra "Plane", "quant_table_set_index[ (version <= 3 ||
      chroma_planes) ? 2 : 1 ]" index is used

   Background: in first implementations of FFV1 bitstream, the index for
   Cb and Cr "Planes" was stored even if it is not used (chroma_planes
   set to 0), this index is kept for version <= 3 in order to keep
   compatibility with FFV1 bitstreams in the wild.

3.7.  Color spaces

   FFV1 supports several color spaces.  The count of allowed coded
   planes and the meaning of the extra "Plane" are determined by the
   selected color space.

   The FFV1 bitstream interleaves data in an order determined by the
   color space.  In YCbCr for each "Plane", each "Line" is coded from
   top to bottom and for each "Line", each "Sample" is coded from left
   to right.  In JPEG2000-RCT for each "Line" from top to bottom, each
   "Plane" is coded and for each "Plane", each "Sample" is encoded from
   left to right.

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3.7.1.  YCbCr

   This color space allows 1 to 4 "Planes".

   The Cb and Cr "Planes" are optional, but if used then MUST be used
   together.  Omitting the Cb and Cr "Planes" codes the frames in
   grayscale without color data.

   An optional transparency "Plane" can be used to code transparency
   data.

   An FFV1 "Frame" using YCbCr MUST use one of the following
   arrangements:

   *  Y

   *  Y, Transparency

   *  Y, Cb, Cr

   *  Y, Cb, Cr, Transparency

   The Y "Plane" MUST be coded first.  If the Cb and Cr "Planes" are
   used then they MUST be coded after the Y "Plane".  If a transparency
   "Plane" is used, then it MUST be coded last.

3.7.2.  RGB

   This color space allows 3 or 4 "Planes".

   An optional transparency "Plane" can be used to code transparency
   data.

   JPEG2000-RCT is a Reversible Color Transform that codes RGB (red,
   green, blue) "Planes" losslessly in a modified YCbCr color space
   [ISO.15444-1.2016].  Reversible Pixel transformations between YCbCr
   and RGB use the following formulae.

   Cb=b-g
   Cr=r-g
   Y=g+(Cb+Cr)>>2
   g=Y-(Cb+Cr)>>2
   r=Cr+g
   b=Cb+g

                                  Figure 3

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   Exception for the JPEG2000-RCT conversion: if bits_per_raw_sample is
   between 9 and 15 inclusive and extra_plane is 0, the following
   formulae for reversible conversions between YCbCr and RGB MUST be
   used instead of the ones above:

   Cb=g-b
   Cr=r-b
   Y=b+(Cb+Cr)>>2
   b=Y-(Cb+Cr)>>2
   r=Cr+b
   g=Cb+b

                                  Figure 4

   Background: At the time of this writing, in all known implementations
   of FFV1 bitstream, when bits_per_raw_sample was between 9 and 15
   inclusive and extra_plane is 0, GBR "Planes" were used as BGR
   "Planes" during both encoding and decoding.  In the meanwhile, 16-bit
   JPEG2000-RCT was implemented without this issue in one implementation
   and validated by one conformance checker.  Methods to address this
   exception for the transform are under consideration for the next
   version of the FFV1 bitstream.

   When FFV1 uses the JPEG2000-RCT, the horizontal "Lines" are
   interleaved to improve caching efficiency since it is most likely
   that the JPEG2000-RCT will immediately be converted to RGB during
   decoding.  The interleaved coding order is also Y, then Cb, then Cr,
   and then if used transparency.

   As an example, a "Frame" that is two "Pixels" wide and two "Pixels"
   high, could be comprised of the following structure:

   +------------------------+------------------------+
   | Pixel(1,1)             | Pixel(2,1)             |
   | Y(1,1) Cb(1,1) Cr(1,1) | Y(2,1) Cb(2,1) Cr(2,1) |
   +------------------------+------------------------+
   | Pixel(1,2)             | Pixel(2,2)             |
   | Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) |
   +------------------------+------------------------+

   In JPEG2000-RCT, the coding order would be left to right and then top
   to bottom, with values interleaved by "Lines" and stored in this
   order:

   Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2)
   Cb(2,2) Cr(1,2) Cr(2,2)

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3.8.  Coding of the Sample Difference

   Instead of coding the n+1 bits of the Sample Difference with Huffman
   or Range coding (or n+2 bits, in the case of JPEG2000-RCT), only the
   n (or n+1, in the case of JPEG2000-RCT) least significant bits are
   used, since this is sufficient to recover the original "Sample".  In
   the equation below, the term "bits" represents bits_per_raw_sample+1
   for JPEG2000-RCT or bits_per_raw_sample otherwise:

   coder_input =
       [(sample_difference + 2^(bits-1)) & (2^bits - 1)] - 2^(bits-1)

                                  Figure 5

3.8.1.  Range Coding Mode

   Early experimental versions of FFV1 used the CABAC Arithmetic coder
   from H.264 as defined in [ISO.14496-10.2014] but due to the uncertain
   patent/royalty situation, as well as its slightly worse performance,
   CABAC was replaced by a Range coder based on an algorithm defined by
   G.  Nigel and N.  Martin in 1979 [range-coding].

3.8.1.1.  Range Binary Values

   To encode binary digits efficiently a Range coder is used.  "C~i~" is
   the i-th Context.  "B~i~" is the i-th byte of the bytestream. "b~i~"
   is the i-th Range coded binary value, "S~0,i~" is the i-th initial
   state.  The length of the bytestream encoding n binary symbols is
   "j~n~" bytes.

   r_{i} = floor( ( R_{i} * S_{i,C_{i}} ) / 2^8 )

                                  Figure 6

   S_{i+1,C_{i}} =  zero_state_{S_{i,C_{i}}} XOR
             l_i =  L_i                      XOR
             t_i =  R_i - r_i                <==
             b_i =  0                        <==>
             L_i <  R_i - r_i

   S_{i+1,C_{i}} =  one_state_{S_{i,C_{i}}}  XOR
             l_i =  L_i - R_i + r_i          XOR
             t_i =  r_i                      <==
             b_i =  1                        <==>
             L_i >= R_i - r_i

                                  Figure 7

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   S_{i+1,k} = S_{i,k} <== C_i != k

                                  Figure 8

   R_{i+1} =  2^8 * t_{i}                   XOR
   L_{i+1} =  2^8 * l_{i} + B_{j_{i}}       XOR
   j_{i+1} =  j_{i} + 1                     <==
   t_{i}   <  2^8

   R_{i+1} =  t_{i}                         XOR
   L_{i+1} =  l_{i}                         XOR
   j_{i+1} =  j_{i}                         <==
   t_{i}   >= 2^8

                                  Figure 9

   R_{0} = 65280

                                 Figure 10

   L_{0} = 2^8 * B_{0} + B_{1}

                                 Figure 11

   j_{0} = 2

                                 Figure 12

3.8.1.1.1.  Termination

   The range coder can be used in 3 modes.

   *  In "Open mode" when decoding, every symbol the reader attempts to
      read is available.  In this mode arbitrary data can have been
      appended without affecting the range coder output.  This mode is
      not used in FFV1.

   *  In "Closed mode" the length in bytes of the bytestream is provided
      to the range decoder.  Bytes beyond the length are read as 0 by
      the range decoder.  This is generally 1 byte shorter than the open
      mode.

   *  In "Sentinel mode" the exact length in bytes is not known and thus
      the range decoder MAY read into the data that follows the range
      coded bytestream by one byte.  In "Sentinel mode", the end of the
      range coded bytestream is a binary symbol with state 129, which
      value SHALL be discarded.  After reading this symbol, the range
      decoder will have read one byte beyond the end of the range coded

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      bytestream.  This way the byte position of the end can be
      determined.  Bytestreams written in "Sentinel mode" can be read in
      "Closed mode" if the length can be determined, in this case the
      last (sentinel) symbol will be read non-corrupted and be of value
      0.

   Above describes the range decoding, encoding is defined as any
   process which produces a decodable bytestream.

   There are 3 places where range coder termination is needed in FFV1.
   First is in the "Configuration Record", in this case the size of the
   range coded bytestream is known and handled as "Closed mode".  Second
   is the switch from the "Slice Header" which is range coded to Golomb
   coded slices as "Sentinel mode".  Third is the end of range coded
   Slices which need to terminate before the CRC at their end.  This can
   be handled as "Sentinel mode" or as "Closed mode" if the CRC position
   has been determined.

3.8.1.2.  Range Non Binary Values

   To encode scalar integers, it would be possible to encode each bit
   separately and use the past bits as context.  However that would mean
   255 contexts per 8-bit symbol that is not only a waste of memory but
   also requires more past data to reach a reasonably good estimate of
   the probabilities.  Alternatively assuming a Laplacian distribution
   and only dealing with its variance and mean (as in Huffman coding)
   would also be possible, however, for maximum flexibility and
   simplicity, the chosen method uses a single symbol to encode if a
   number is 0, and if not, encodes the number using its exponent,
   mantissa and sign.  The exact contexts used are best described by the
   following code, followed by some comments.

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   void put_symbol(RangeCoder *c, uint8_t *state, int v, int \   |
   is_signed) {                                                  |
       int i;                                                    |
       put_rac(c, state+0, !v);                                  |
       if (v) {                                                  |
           int a= abs(v);                                        |
           int e= log2(a);                                       |
                                                                 |
           for (i = 0; i < e; i++) {                             |
               put_rac(c, state+1+min(i,9), 1);  //1..10         |
           }                                                     |
                                                                 |
           put_rac(c, state+1+min(i,9), 0);                      |
           for (i = e-1; i >= 0; i--) {                          |
               put_rac(c, state+22+min(i,9), (a>>i)&1); //22..31 |
           }                                                     |
                                                                 |
           if (is_signed) {                                      |
               put_rac(c, state+11 + min(e, 10), v < 0); //11..21|
           }                                                     |
       }                                                         |
   }                                                             |

3.8.1.3.  Initial Values for the Context Model

   At keyframes all Range coder state variables are set to their initial
   state.

3.8.1.4.  State Transition Table

   one_state_{i} =
          default_state_transition_{i} + state_transition_delta_{i}

                                 Figure 13

   zero_state_{i} = 256 - one_state_{256-i}

                                 Figure 14

3.8.1.5.  default_state_transition

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     0,  0,  0,  0,  0,  0,  0,  0, 20, 21, 22, 23, 24, 25, 26, 27,

    28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42,

    43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57,

    58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,

    74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88,

    89, 90, 91, 92, 93, 94, 94, 95, 96, 97, 98, 99,100,101,102,103,

   104,105,106,107,108,109,110,111,112,113,114,114,115,116,117,118,

   119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,133,

   134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,

   150,151,152,152,153,154,155,156,157,158,159,160,161,162,163,164,

   165,166,167,168,169,170,171,171,172,173,174,175,176,177,178,179,

   180,181,182,183,184,185,186,187,188,189,190,190,191,192,194,194,

   195,196,197,198,199,200,201,202,202,204,205,206,207,208,209,209,

   210,211,212,213,215,215,216,217,218,219,220,220,222,223,224,225,

   226,227,227,229,229,230,231,232,234,234,235,236,237,238,239,240,

   241,242,243,244,245,246,247,248,248,  0,  0,  0,  0,  0,  0,  0,

3.8.1.6.  Alternative State Transition Table

   The alternative state transition table has been built using iterative
   minimization of frame sizes and generally performs better than the
   default.  To use it, the coder_type (see the section on coder_type
   (#codertype)) MUST be set to 2 and the difference to the default MUST
   be stored in the "Parameters", see the section on Parameters
   (#parameters).  The reference implementation of FFV1 in FFmpeg uses
   this table by default at the time of this writing when Range coding
   is used.

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     0, 10, 10, 10, 10, 16, 16, 16, 28, 16, 16, 29, 42, 49, 20, 49,

    59, 25, 26, 26, 27, 31, 33, 33, 33, 34, 34, 37, 67, 38, 39, 39,

    40, 40, 41, 79, 43, 44, 45, 45, 48, 48, 64, 50, 51, 52, 88, 52,

    53, 74, 55, 57, 58, 58, 74, 60,101, 61, 62, 84, 66, 66, 68, 69,

    87, 82, 71, 97, 73, 73, 82, 75,111, 77, 94, 78, 87, 81, 83, 97,

    85, 83, 94, 86, 99, 89, 90, 99,111, 92, 93,134, 95, 98,105, 98,

   105,110,102,108,102,118,103,106,106,113,109,112,114,112,116,125,

   115,116,117,117,126,119,125,121,121,123,145,124,126,131,127,129,

   165,130,132,138,133,135,145,136,137,139,146,141,143,142,144,148,

   147,155,151,149,151,150,152,157,153,154,156,168,158,162,161,160,

   172,163,169,164,166,184,167,170,177,174,171,173,182,176,180,178,

   175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196,

   197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214,

   209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225,

   226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242,

   241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255,

3.8.2.  Golomb Rice Mode

   The end of the bitstream of the "Frame" is filled with 0-bits until
   that the bitstream contains a multiple of 8 bits.

3.8.2.1.  Signed Golomb Rice Codes

   This coding mode uses Golomb Rice codes.  The VLC is split into 2
   parts, the prefix stores the most significant bits and the suffix
   stores the k least significant bits or stores the whole number in the
   ESC case.

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   int get_ur_golomb(k) {                                        |
       for (prefix = 0; prefix < 12; prefix++) {                 |
           if (get_bits(1)) {                                    |
               return get_bits(k) + (prefix << k)                |
           }                                                     |
       }                                                         |
       return get_bits(bits) + 11                                |
   }                                                             |
                                                                 |
   int get_sr_golomb(k) {                                        |
       v = get_ur_golomb(k);                                     |
       if (v & 1) return - (v >> 1) - 1;                         |
       else       return   (v >> 1);                             |
   }

3.8.2.1.1.  Prefix

                        +----------------+-------+
                        | bits           | value |
                        +================+=======+
                        | 1              | 0     |
                        +----------------+-------+
                        | 01             | 1     |
                        +----------------+-------+
                        | ...            | ...   |
                        +----------------+-------+
                        | 0000 0000 0001 | 11    |
                        +----------------+-------+
                        | 0000 0000 0000 | ESC   |
                        +----------------+-------+

                                 Table 1

3.8.2.1.2.  Suffix

      +---------+--------------------------------------------------+
      +=========+==================================================+
      | non ESC | the k least significant bits MSB first           |
      +---------+--------------------------------------------------+
      | ESC     | the value - 11, in MSB first order, ESC may only |
      |         | be used if the value cannot be coded as non ESC  |
      +---------+--------------------------------------------------+

                                 Table 2

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3.8.2.1.3.  Examples

                 +-----+-------------------------+-------+
                 |  k  | bits                    | value |
                 +=====+=========================+=======+
                 |  0  | "1"                     |     0 |
                 +-----+-------------------------+-------+
                 |  0  | "001"                   |     2 |
                 +-----+-------------------------+-------+
                 |  2  | "1 00"                  |     0 |
                 +-----+-------------------------+-------+
                 |  2  | "1 10"                  |     2 |
                 +-----+-------------------------+-------+
                 |  2  | "01 01"                 |     5 |
                 +-----+-------------------------+-------+
                 | any | "000000000000 10000000" |   139 |
                 +-----+-------------------------+-------+

                                  Table 3

3.8.2.2.  Run Mode

   Run mode is entered when the context is 0 and left as soon as a non-0
   difference is found.  The level is identical to the predicted one.
   The run and the first different level are coded.

3.8.2.2.1.  Run Length Coding

   The run value is encoded in 2 parts, the prefix part stores the more
   significant part of the run as well as adjusting the run_index that
   determines the number of bits in the less significant part of the
   run.  The 2nd part of the value stores the less significant part of
   the run as it is.  The run_index is reset for each "Plane" and slice
   to 0.

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   log2_run[41]={                                                |
    0, 0, 0, 0, 1, 1, 1, 1,                                      |
    2, 2, 2, 2, 3, 3, 3, 3,                                      |
    4, 4, 5, 5, 6, 6, 7, 7,                                      |
    8, 9,10,11,12,13,14,15,                                      |
   16,17,18,19,20,21,22,23,                                      |
   24,                                                           |
   };                                                            |
                                                                 |
   if (run_count == 0 && run_mode == 1) {                        |
       if (get_bits(1)) {                                        |
           run_count = 1 << log2_run[run_index];                 |
           if (x + run_count <= w) {                             |
               run_index++;                                      |
           }                                                     |
       } else {                                                  |
           if (log2_run[run_index]) {                            |
               run_count = get_bits(log2_run[run_index]);        |
           } else {                                              |
               run_count = 0;                                    |
           }                                                     |
           if (run_index) {                                      |
               run_index--;                                      |
           }                                                     |
           run_mode = 2;                                         |
       }                                                         |
   }                                                             |

   The log2_run function is also used within [ISO.14495-1.1999].

3.8.2.2.2.  Level Coding

   Level coding is identical to the normal difference coding with the
   exception that the 0 value is removed as it cannot occur:

       diff = get_vlc_symbol(context_state);
       if (diff >= 0) {
           diff++;
       }

   Note, this is different from JPEG-LS, which doesn't use prediction in
   run mode and uses a different encoding and context model for the last
   difference On a small set of test "Samples" the use of prediction
   slightly improved the compression rate.

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3.8.2.3.  Scalar Mode

   Each difference is coded with the per context mean prediction removed
   and a per context value for k.

   get_vlc_symbol(state) {
       i = state->count;
       k = 0;
       while (i < state->error_sum) {
           k++;
           i += i;
       }

       v = get_sr_golomb(k);

       if (2 * state->drift < -state->count) {
           v = -1 - v;
       }

       ret = sign_extend(v + state->bias, bits);

       state->error_sum += abs(v);
       state->drift     += v;

       if (state->count == 128) {
           state->count     >>= 1;
           state->drift     >>= 1;
           state->error_sum >>= 1;
       }
       state->count++;
       if (state->drift <= -state->count) {
           state->bias = max(state->bias - 1, -128);

           state->drift = max(state->drift + state->count,
                              -state->count + 1);
       } else if (state->drift > 0) {
           state->bias = min(state->bias + 1, 127);

           state->drift = min(state->drift - state->count, 0);
       }

       return ret;
   }

3.8.2.4.  Initial Values for the VLC context state

   At keyframes all coder state variables are set to their initial
   state.

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       drift     = 0;
       error_sum = 4;
       bias      = 0;
       count     = 1;

4.  Bitstream

   An FFV1 bitstream is composed of a series of 1 or more "Frames" and
   (when required) a "Configuration Record".

   Within the following sub-sections, pseudo-code is used to explain the
   structure of each FFV1 bitstream component, as described in the
   section on Pseudo-Code (#pseudocode).  The following table lists
   symbols used to annotate that pseudo-code in order to define the
   storage of the data referenced in that line of pseudo-code.

          +--------+-------------------------------------------+
          | Symbol | Definition                                |
          +========+===========================================+
          | u(n)   | unsigned big endian integer using n bits  |
          +--------+-------------------------------------------+
          | sg     | Golomb Rice coded signed scalar symbol    |
          |        | coded with the method described in Signed |
          |        | Golomb Rice Codes (#golomb-rice-mode)     |
          +--------+-------------------------------------------+
          | br     | Range coded Boolean (1-bit) symbol with   |
          |        | the method described in Range binary      |
          |        | values (#range-binary-values)             |
          +--------+-------------------------------------------+
          | ur     | Range coded unsigned scalar symbol coded  |
          |        | with the method described in Range non    |
          |        | binary values (#range-non-binary-values)  |
          +--------+-------------------------------------------+
          | sr     | Range coded signed scalar symbol coded    |
          |        | with the method described in Range non    |
          |        | binary values (#range-non-binary-values)  |
          +--------+-------------------------------------------+

                                 Table 4

   The same context that is initialized to 128 is used for all fields in
   the header.

   The following MUST be provided by external means during
   initialization of the decoder:

   "frame_pixel_width" is defined as "Frame" width in "Pixels".

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   "frame_pixel_height" is defined as "Frame" height in "Pixels".

   Default values at the decoder initialization phase:

   "ConfigurationRecordIsPresent" is set to 0.

4.1.  Parameters

   The "Parameters" section contains significant characteristics about
   the decoding configuration used for all instances of "Frame" (in FFV1
   version 0 and 1) or the whole FFV1 bitstream (other versions),
   including the stream version, color configuration, and quantization
   tables.  The pseudo-code below describes the contents of the
   bitstream.

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   Parameters( ) {                                               |
       version                                                   | ur
       if (version >= 3) {                                       |
           micro_version                                         | ur
       }                                                         |
       coder_type                                                | ur
       if (coder_type > 1) {                                     |
           for (i = 1; i < 256; i++) {                           |
               state_transition_delta[ i ]                       | sr
           }                                                     |
       }                                                         |
       colorspace_type                                           | ur
       if (version >= 1) {                                       |
           bits_per_raw_sample                                   | ur
       }                                                         |
       chroma_planes                                             | br
       log2_h_chroma_subsample                                   | ur
       log2_v_chroma_subsample                                   | ur
       extra_plane                                               | br
       if (version >= 3) {                                       |
           num_h_slices - 1                                      | ur
           num_v_slices - 1                                      | ur
           quant_table_set_count                                 | ur
       }                                                         |
       for (i = 0; i < quant_table_set_count; i++) {             |
           QuantizationTableSet( i )                             |
       }                                                         |
       if (version >= 3) {                                       |
           for (i = 0; i < quant_table_set_count; i++) {         |
               states_coded                                      | br
               if (states_coded) {                               |
                   for (j = 0; j < context_count[ i ]; j++) {    |
                       for (k = 0; k < CONTEXT_SIZE; k++) {      |
                           initial_state_delta[ i ][ j ][ k ]    | sr
                       }                                         |
                   }                                             |
               }                                                 |
           }                                                     |
           ec                                                    | ur
           intra                                                 | ur
       }                                                         |
   }                                                             |

   CONTEXT_SIZE is 32.

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4.1.1.  version

   "version" specifies the version of the FFV1 bitstream.

   Each version is incompatible with other versions: decoders SHOULD
   reject a file due to an unknown version.

   Decoders SHOULD reject a file with version <= 1 &&
   ConfigurationRecordIsPresent == 1.

   Decoders SHOULD reject a file with version >= 3 &&
   ConfigurationRecordIsPresent == 0.

                    +-------+-------------------------+
                    | value | version                 |
                    +=======+=========================+
                    | 0     | FFV1 version 0          |
                    +-------+-------------------------+
                    | 1     | FFV1 version 1          |
                    +-------+-------------------------+
                    | 2     | reserved*               |
                    +-------+-------------------------+
                    | 3     | FFV1 version 3          |
                    +-------+-------------------------+
                    | Other | reserved for future use |
                    +-------+-------------------------+

                                  Table 5

   * Version 2 was never enabled in the encoder thus version 2 files
   SHOULD NOT exist, and this document does not describe them to keep
   the text simpler.

4.1.2.  micro_version

   "micro_version" specifies the micro-version of the FFV1 bitstream.

   After a version is considered stable (a micro-version value is
   assigned to be the first stable variant of a specific version), each
   new micro-version after this first stable variant is compatible with
   the previous micro-version: decoders SHOULD NOT reject a file due to
   an unknown micro-version equal or above the micro-version considered
   as stable.

   Meaning of micro_version for version 3:

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                    +-------+-------------------------+
                    | value | micro_version           |
                    +=======+=========================+
                    | 0...3 | reserved*               |
                    +-------+-------------------------+
                    | 4     | first stable variant    |
                    +-------+-------------------------+
                    | Other | reserved for future use |
                    +-------+-------------------------+

                                  Table 6

   * development versions may be incompatible with the stable variants.

4.1.3.  coder_type

   "coder_type" specifies the coder used.

        +-------+-------------------------------------------------+
        | value | coder used                                      |
        +=======+=================================================+
        | 0     | Golomb Rice                                     |
        +-------+-------------------------------------------------+
        | 1     | Range Coder with default state transition table |
        +-------+-------------------------------------------------+
        | 2     | Range Coder with custom state transition table  |
        +-------+-------------------------------------------------+
        | Other | reserved for future use                         |
        +-------+-------------------------------------------------+

                                  Table 7

4.1.4.  state_transition_delta

   "state_transition_delta" specifies the Range coder custom state
   transition table.

   If state_transition_delta is not present in the FFV1 bitstream, all
   Range coder custom state transition table elements are assumed to be
   0.

4.1.5.  colorspace_type

   "colorspace_type" specifies the color space encoded, the pixel
   transformation used by the encoder, the extra plane content, as well
   as interleave method.

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   +-------+-------------+----------------+--------------+-------------+
   | value | color space | pixel          | extra plane  | interleave  |
   |       | encoded     | transformation | content      | method      |
   +=======+=============+================+==============+=============+
   | 0     | YCbCr       | None           | Transparency | "Plane"     |
   |       |             |                |              | then        |
   |       |             |                |              | "Line"      |
   +-------+-------------+----------------+--------------+-------------+
   | 1     | RGB         | JPEG2000-RCT   | Transparency | "Line"      |
   |       |             |                |              | then        |
   |       |             |                |              | "Plane"     |
   +-------+-------------+----------------+--------------+-------------+
   | Other | reserved    | reserved for   | reserved for | reserved    |
   |       | for future  | future use     | future use   | for future  |
   |       | use         |                |              | use         |
   +-------+-------------+----------------+--------------+-------------+

                                  Table 8

   Restrictions:

   If "colorspace_type" is 1, then "chroma_planes" MUST be 1,
   "log2_h_chroma_subsample" MUST be 0, and "log2_v_chroma_subsample"
   MUST be 0.

4.1.6.  chroma_planes

   "chroma_planes" indicates if chroma (color) "Planes" are present.

                +-------+---------------------------------+
                | value | presence                        |
                +=======+=================================+
                | 0     | chroma "Planes" are not present |
                +-------+---------------------------------+
                | 1     | chroma "Planes" are present     |
                +-------+---------------------------------+

                                  Table 9

4.1.7.  bits_per_raw_sample

   "bits_per_raw_sample" indicates the number of bits for each "Sample".
   Inferred to be 8 if not present.

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               +-------+-----------------------------------+
               | value | bits for each sample              |
               +=======+===================================+
               | 0     | reserved*                         |
               +-------+-----------------------------------+
               | Other | the actual bits for each "Sample" |
               +-------+-----------------------------------+

                                  Table 10

   * Encoders MUST NOT store bits_per_raw_sample = 0 Decoders SHOULD
   accept and interpret bits_per_raw_sample = 0 as 8.

4.1.8.  log2_h_chroma_subsample

   "log2_h_chroma_subsample" indicates the subsample factor, stored in
   powers to which the number 2 must be raised, between luma and chroma
   width ("chroma_width = 2^-log2_h_chroma_subsample^ * luma_width").

4.1.9.  log2_v_chroma_subsample

   "log2_v_chroma_subsample" indicates the subsample factor, stored in
   powers to which the number 2 must be raised, between luma and chroma
   height ("chroma_height=2^-log2_v_chroma_subsample^ * luma_height").

4.1.10.  extra_plane

   "extra_plane" indicates if an extra "Plane" is present.

                 +-------+------------------------------+
                 | value | presence                     |
                 +=======+==============================+
                 | 0     | extra "Plane" is not present |
                 +-------+------------------------------+
                 | 1     | extra "Plane" is present     |
                 +-------+------------------------------+

                                 Table 11

4.1.11.  num_h_slices

   "num_h_slices" indicates the number of horizontal elements of the
   slice raster.

   Inferred to be 1 if not present.

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4.1.12.  num_v_slices

   "num_v_slices" indicates the number of vertical elements of the slice
   raster.

   Inferred to be 1 if not present.

4.1.13.  quant_table_set_count

   "quant_table_set_count" indicates the number of Quantization
   Table Sets. "quant_table_set_count" MUST be less than or equal to 8.

   Inferred to be 1 if not present.

   MUST NOT be 0.

4.1.14.  states_coded

   "states_coded" indicates if the respective Quantization Table Set has
   the initial states coded.

   Inferred to be 0 if not present.

                +-------+--------------------------------+
                | value | initial states                 |
                +=======+================================+
                | 0     | initial states are not present |
                |       | and are assumed to be all 128  |
                +-------+--------------------------------+
                | 1     | initial states are present     |
                +-------+--------------------------------+

                                 Table 12

4.1.15.  initial_state_delta

   "initial_state_delta[ i ][ j ][ k ]" indicates the initial Range
   coder state, it is encoded using "k" as context index and

   pred = j ? initial_states[ i ][j - 1][ k ]

                                 Figure 15

   initial_state[ i ][ j ][ k ] =
          ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255

                                 Figure 16

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4.1.16.  ec

   "ec" indicates the error detection/correction type.

          +-------+--------------------------------------------+
          | value | error detection/correction type            |
          +=======+============================================+
          | 0     | 32-bit CRC on the global header            |
          +-------+--------------------------------------------+
          | 1     | 32-bit CRC per slice and the global header |
          +-------+--------------------------------------------+
          | Other | reserved for future use                    |
          +-------+--------------------------------------------+

                                 Table 13

4.1.17.  intra

   "intra" indicates the relationship between the instances of "Frame".

   Inferred to be 0 if not present.

              +-------+-------------------------------------+
              | value | relationship                        |
              +=======+=====================================+
              | 0     | Frames are independent or dependent |
              |       | (keyframes and non keyframes)       |
              +-------+-------------------------------------+
              | 1     | Frames are independent (keyframes   |
              |       | only)                               |
              +-------+-------------------------------------+
              | Other | reserved for future use             |
              +-------+-------------------------------------+

                                  Table 14

4.2.  Configuration Record

   In the case of a FFV1 bitstream with "version >= 3", a "Configuration
   Record" is stored in the underlying "Container", at the track header
   level.  It contains the "Parameters" used for all instances of
   "Frame".  The size of the "Configuration Record", "NumBytes", is
   supplied by the underlying "Container".

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   pseudo-code                                                | type
   -----------------------------------------------------------|-----
   ConfigurationRecord( NumBytes ) {                          |
       ConfigurationRecordIsPresent = 1                       |
       Parameters( )                                          |
       while (remaining_symbols_in_syntax(NumBytes - 4)) {    |
           reserved_for_future_use                            | br/ur/sr
       }                                                      |
       configuration_record_crc_parity                        | u(32)
   }                                                          |

4.2.1.  reserved_for_future_use

   "reserved_for_future_use" has semantics that are reserved for future
   use.

   Encoders conforming to this version of this specification SHALL NOT
   write this value.

   Decoders conforming to this version of this specification SHALL
   ignore its value.

4.2.2.  configuration_record_crc_parity

   "configuration_record_crc_parity" 32 bits that are chosen so that the
   "Configuration Record" as a whole has a crc remainder of 0.

   This is equivalent to storing the crc remainder in the 32-bit parity.

   The CRC generator polynomial used is the standard IEEE CRC polynomial
   (0x104C11DB7) with initial value 0.

4.2.3.  Mapping FFV1 into Containers

   This "Configuration Record" can be placed in any file format
   supporting "Configuration Records", fitting as much as possible with
   how the file format uses to store "Configuration Records".  The
   "Configuration Record" storage place and "NumBytes" are currently
   defined and supported by this version of this specification for the
   following formats:

4.2.3.1.  AVI File Format

   The "Configuration Record" extends the stream format chunk ("AVI ",
   "hdlr", "strl", "strf") with the ConfigurationRecord bitstream.

   See [AVI] for more information about chunks.

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   "NumBytes" is defined as the size, in bytes, of the strf chunk
   indicated in the chunk header minus the size of the stream format
   structure.

4.2.3.2.  ISO Base Media File Format

   The "Configuration Record" extends the sample description box
   ("moov", "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box
   that contains the ConfigurationRecord bitstream.  See
   [ISO.14496-12.2015] for more information about boxes.

   "NumBytes" is defined as the size, in bytes, of the "glbl" box
   indicated in the box header minus the size of the box header.

4.2.3.3.  NUT File Format

   The codec_specific_data element (in "stream_header" packet) contains
   the ConfigurationRecord bitstream.  See [NUT] for more information
   about elements.

   "NumBytes" is defined as the size, in bytes, of the
   codec_specific_data element as indicated in the "length" field of
   codec_specific_data

4.2.3.4.  Matroska File Format

   FFV1 SHOULD use "V_FFV1" as the Matroska "Codec ID".  For FFV1
   versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be
   used.  For FFV1 versions 3 or greater, the Matroska "CodecPrivate"
   Element MUST contain the FFV1 "Configuration Record" structure and no
   other data.  See [Matroska] for more information about elements.

   "NumBytes" is defined as the "Element Data Size" of the
   "CodecPrivate" Element.

4.3.  Frame

   A "Frame" is an encoded representation of a complete static image.
   The whole "Frame" is provided by the underlaying container.

   A "Frame" consists of the keyframe field, "Parameters" (if version
   <=1), and a sequence of independent slices.  The pseudo-code below
   describes the contents of a "Frame".

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   Frame( NumBytes ) {                                           |
       keyframe                                                  | br
       if (keyframe && !ConfigurationRecordIsPresent {           |
           Parameters( )                                         |
       }                                                         |
       while (remaining_bits_in_bitstream( NumBytes )) {         |
           Slice( )                                              |
       }                                                         |
   }                                                             |

   Architecture overview of slices in a "Frame":

    +-----------------------------------------------------------------+
    +=================================================================+
    | first slice header                                              |
    +-----------------------------------------------------------------+
    | first slice content                                             |
    +-----------------------------------------------------------------+
    | first slice footer                                              |
    +-----------------------------------------------------------------+
    | --------------------------------------------------------------- |
    +-----------------------------------------------------------------+
    | second slice header                                             |
    +-----------------------------------------------------------------+
    | second slice content                                            |
    +-----------------------------------------------------------------+
    | second slice footer                                             |
    +-----------------------------------------------------------------+
    | --------------------------------------------------------------- |
    +-----------------------------------------------------------------+
    | ...                                                             |
    +-----------------------------------------------------------------+
    | --------------------------------------------------------------- |
    +-----------------------------------------------------------------+
    | last slice header                                               |
    +-----------------------------------------------------------------+
    | last slice content                                              |
    +-----------------------------------------------------------------+
    | last slice footer                                               |
    +-----------------------------------------------------------------+

                                  Table 15

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4.4.  Slice

   A "Slice" is an independent spatial sub-section of a "Frame" that is
   encoded separately from an other region of the same "Frame".  The use
   of more than one "Slice" per "Frame" can be useful for taking
   advantage of the opportunities of multithreaded encoding and
   decoding.

   A "Slice" consists of a "Slice Header" (when relevant), a "Slice
   Content", and a "Slice Footer" (when relevant).  The pseudo-code
   below describes the contents of a "Slice".

   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   Slice( ) {                                                    |
       if (version >= 3) {                                       |
           SliceHeader( )                                        |
       }                                                         |
       SliceContent( )                                           |
       if (coder_type == 0) {                                    |
           while (!byte_aligned()) {                             |
               padding                                           | u(1)
           }                                                     |
       }                                                         |
       if (version <= 1) {                                       |
           while (remaining_bits_in_bitstream( NumBytes ) != 0) {|
               reserved                                          | u(1)
           }                                                     |
       }                                                         |
       if (version >= 3) {                                       |
           SliceFooter( )                                        |
       }                                                         |
   }                                                             |

   "padding" specifies a bit without any significance and used only for
   byte alignment.  MUST be 0.

   "reserved" specifies a bit without any significance in this revision
   of the specification and may have a significance in a later revision
   of this specification.

   Encoders SHOULD NOT fill these bits.

   Decoders SHOULD ignore these bits.

   Note in case these bits are used in a later revision of this
   specification: any revision of this specification SHOULD care about
   avoiding to add 40 bits of content after "SliceContent" for version 0

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   and 1 of the bitstream.  Background: due to some non conforming
   encoders, some bitstreams where found with 40 extra bits
   corresponding to "error_status" and "slice_crc_parity", a decoder
   conforming to the revised specification could not do the difference
   between a revised bitstream and a buggy bitstream.

4.5.  Slice Header

   A "Slice Header" provides information about the decoding
   configuration of the "Slice", such as its spatial position, size, and
   aspect ratio.  The pseudo-code below describes the contents of the
   "Slice Header".

   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   SliceHeader( ) {                                              |
       slice_x                                                   | ur
       slice_y                                                   | ur
       slice_width - 1                                           | ur
       slice_height - 1                                          | ur
       for (i = 0; i < quant_table_set_index_count; i++) {       |
           quant_table_set_index[ i ]                            | ur
       }                                                         |
       picture_structure                                         | ur
       sar_num                                                   | ur
       sar_den                                                   | ur
   }                                                             |

4.5.1.  slice_x

   "slice_x" indicates the x position on the slice raster formed by
   num_h_slices.

   Inferred to be 0 if not present.

4.5.2.  slice_y

   "slice_y" indicates the y position on the slice raster formed by
   num_v_slices.

   Inferred to be 0 if not present.

4.5.3.  slice_width

   "slice_width" indicates the width on the slice raster formed by
   num_h_slices.

   Inferred to be 1 if not present.

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4.5.4.  slice_height

   "slice_height" indicates the height on the slice raster formed by
   num_v_slices.

   Inferred to be 1 if not present.

4.5.5.  quant_table_set_index_count

   "quant_table_set_index_count" is defined as "1 + ( ( chroma_planes ||
   version <= 3 ) ? 1 : 0 ) + ( extra_plane ? 1 : 0 )".

4.5.6.  quant_table_set_index

   "quant_table_set_index" indicates the Quantization Table Set index to
   select the Quantization Table Set and the initial states for the
   slice.

   Inferred to be 0 if not present.

4.5.7.  picture_structure

   "picture_structure" specifies the temporal and spatial relationship
   of each "Line" of the "Frame".

   Inferred to be 0 if not present.

                    +-------+-------------------------+
                    | value | picture structure used  |
                    +=======+=========================+
                    | 0     | unknown                 |
                    +-------+-------------------------+
                    | 1     | top field first         |
                    +-------+-------------------------+
                    | 2     | bottom field first      |
                    +-------+-------------------------+
                    | 3     | progressive             |
                    +-------+-------------------------+
                    | Other | reserved for future use |
                    +-------+-------------------------+

                                  Table 16

4.5.8.  sar_num

   "sar_num" specifies the "Sample" aspect ratio numerator.

   Inferred to be 0 if not present.

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   A value of 0 means that aspect ratio is unknown.

   Encoders MUST write 0 if "Sample" aspect ratio is unknown.

   If "sar_den" is 0, decoders SHOULD ignore the encoded value and
   consider that "sar_num" is 0.

4.5.9.  sar_den

   "sar_den" specifies the "Sample" aspect ratio denominator.

   Inferred to be 0 if not present.

   A value of 0 means that aspect ratio is unknown.

   Encoders MUST write 0 if "Sample" aspect ratio is unknown.

   If "sar_num" is 0, decoders SHOULD ignore the encoded value and
   consider that "sar_den" is 0.

4.6.  Slice Content

   A "Slice Content" contains all "Line" elements part of the "Slice".

   Depending on the configuration, "Line" elements are ordered by
   "Plane" then by row (YCbCr) or by row then by "Plane" (RGB).

   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   SliceContent( ) {                                             |
       if (colorspace_type == 0) {                               |
           for (p = 0; p < primary_color_count; p++) {           |
               for (y = 0; y < plane_pixel_height[ p ]; y++) {   |
                   Line( p, y )                                  |
               }                                                 |
           }                                                     |
       } else if (colorspace_type == 1) {                        |
           for (y = 0; y < slice_pixel_height; y++) {            |
               for (p = 0; p < primary_color_count; p++) {       |
                   Line( p, y )                                  |
               }                                                 |
           }                                                     |
       }                                                         |
   }                                                             |

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4.6.1.  primary_color_count

   "primary_color_count" is defined as "1 + ( chroma_planes ? 2 : 0 ) +
   ( extra_plane ? 1 : 0 )".

4.6.2.  plane_pixel_height

   "plane_pixel_height[ p ]" is the height in pixels of plane p of the
   slice.

   "plane_pixel_height[ 0 ]" and "plane_pixel_height[ 1 + (
   chroma_planes ? 2 : 0 ) ]" value is "slice_pixel_height".

   If "chroma_planes" is set to 1, "plane_pixel_height[ 1 ]" and
   "plane_pixel_height[ 2 ]" value is "ceil( slice_pixel_height /
   log2_v_chroma_subsample )".

4.6.3.  slice_pixel_height

   "slice_pixel_height" is the height in pixels of the slice.

   Its value is "floor( ( slice_y + slice_height ) * slice_pixel_height
   / num_v_slices ) - slice_pixel_y".

4.6.4.  slice_pixel_y

   "slice_pixel_y" is the slice vertical position in pixels.

   Its value is "floor( slice_y * frame_pixel_height / num_v_slices )".

4.7.  Line

   A "Line" is a list of the sample differences (relative to the
   predictor) of primary color components.  The pseudo-code below
   describes the contents of the "Line".

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   Line( p, y ) {                                                |
       if (colorspace_type == 0) {                               |
           for (x = 0; x < plane_pixel_width[ p ]; x++) {        |
               sample_difference[ p ][ y ][ x ]                  |
           }                                                     |
       } else if (colorspace_type == 1) {                        |
           for (x = 0; x < slice_pixel_width; x++) {             |
               sample_difference[ p ][ y ][ x ]                  |
           }                                                     |
       }                                                         |
   }                                                             |

4.7.1.  plane_pixel_width

   "plane_pixel_width[ p ]" is the width in "Pixels" of "Plane" p of the
   slice.

   "plane_pixel_width[ 0 ]" and "plane_pixel_width[ 1 + ( chroma_planes
   ? 2 : 0 ) ]" value is "slice_pixel_width".

   If "chroma_planes" is set to 1, "plane_pixel_width[ 1 ]" and
   "plane_pixel_width[ 2 ]" value is "ceil( slice_pixel_width / (1 <<
   log2_h_chroma_subsample) )".

4.7.2.  slice_pixel_width

   "slice_pixel_width" is the width in "Pixels" of the slice.

   Its value is "floor( ( slice_x + slice_width ) * slice_pixel_width /
   num_h_slices ) - slice_pixel_x".

4.7.3.  slice_pixel_x

   "slice_pixel_x" is the slice horizontal position in "Pixels".

   Its value is "floor( slice_x * frame_pixel_width / num_h_slices )".

4.7.4.  sample_difference

   "sample_difference[ p ][ y ][ x ]" is the sample difference for
   "Sample" at "Plane" "p", y position "y", and x position "x".  The
   "Sample" value is computed based on median predictor and context
   described in the section on Samples (#samples).

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4.8.  Slice Footer

   A "Slice Footer" provides information about slice size and
   (optionally) parity.  The pseudo-code below describes the contents of
   the "Slice Footer".

   Note: "Slice Footer" is always byte aligned.

   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   SliceFooter( ) {                                              |
       slice_size                                                | u(24)
       if (ec) {                                                 |
           error_status                                          | u(8)
           slice_crc_parity                                      | u(32)
       }                                                         |
   }                                                             |

4.8.1.  slice_size

   "slice_size" indicates the size of the slice in bytes.

   Note: this allows finding the start of slices before previous slices
   have been fully decoded, and allows parallel decoding as well as
   error resilience.

4.8.2.  error_status

   "error_status" specifies the error status.

             +-------+--------------------------------------+
             | value | error status                         |
             +=======+======================================+
             | 0     | no error                             |
             +-------+--------------------------------------+
             | 1     | slice contains a correctable error   |
             +-------+--------------------------------------+
             | 2     | slice contains a uncorrectable error |
             +-------+--------------------------------------+
             | Other | reserved for future use              |
             +-------+--------------------------------------+

                                 Table 17

4.8.3.  slice_crc_parity

   "slice_crc_parity" 32 bits that are chosen so that the slice as a
   whole has a crc remainder of 0.

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   This is equivalent to storing the crc remainder in the 32-bit parity.

   The CRC generator polynomial used is the standard IEEE CRC polynomial
   (0x104C11DB7) with initial value 0.

4.9.  Quantization Table Set

   The Quantization Table Sets are stored by storing the number of equal
   entries -1 of the first half of the table (represented as "len - 1"
   in the pseudo-code below) using the method described in Range Non
   Binary Values (#range-non-binary-values).  The second half doesn't
   need to be stored as it is identical to the first with flipped sign.
   "scale" and "len_count[ i ][ j ]" are temporary values used for the
   computing of "context_count[ i ]" and are not used outside
   Quantization Table Set pseudo-code.

   Example:

   Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0

   Stored values: 1, 3, 1

   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   QuantizationTableSet( i ) {                                   |
       scale = 1                                                 |
       for (j = 0; j < MAX_CONTEXT_INPUTS; j++) {                |
           QuantizationTable( i, j, scale )                      |
           scale *= 2 * len_count[ i ][ j ] - 1                  |
       }                                                         |
       context_count[ i ] = ceil( scale / 2 )                    |
   }                                                             |

   MAX_CONTEXT_INPUTS is 5.

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   pseudo-code                                                   | type
   --------------------------------------------------------------|-----
   QuantizationTable(i, j, scale) {                              |
       v = 0                                                     |
       for (k = 0; k < 128;) {                                   |
           len - 1                                               | ur
           for (a = 0; a < len; a++) {                           |
               quant_tables[ i ][ j ][ k ] = scale * v           |
               k++                                               |
           }                                                     |
           v++                                                   |
       }                                                         |
       for (k = 1; k < 128; k++) {                               |
           quant_tables[ i ][ j ][ 256 - k ] = \                 |
           -quant_tables[ i ][ j ][ k ]                          |
       }                                                         |
       quant_tables[ i ][ j ][ 128 ] = \                         |
       -quant_tables[ i ][ j ][ 127 ]                            |
       len_count[ i ][ j ] = v                                   |
   }                                                             |

4.9.1.  quant_tables

   "quant_tables[ i ][ j ][ k ]" indicates the quantification table
   value of the Quantized Sample Difference "k" of the Quantization
   Table "j" of the Set Quantization Table Set "i".

4.9.2.  context_count

   "context_count[ i ]" indicates the count of contexts for Quantization
   Table Set "i". "context_count[ i ]" MUST be less than or equal to
   32768.

5.  Restrictions

   To ensure that fast multithreaded decoding is possible, starting with
   version 3 and if "frame_pixel_width * frame_pixel_height" is more
   than 101376, "slice_width * slice_height" MUST be less or equal to
   "num_h_slices * num_v_slices / 4".  Note: 101376 is the frame size in
   "Pixels" of a 352x288 frame also known as CIF ("Common Intermediate
   Format") frame size format.

   For each "Frame", each position in the slice raster MUST be filled by
   one and only one slice of the "Frame" (no missing slice position, no
   slice overlapping).

   For each "Frame" with keyframe value of 0, each slice MUST have the

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   same value of "slice_x, slice_y, slice_width, slice_height" as a
   slice in the previous "Frame".

6.  Security Considerations

   Like any other codec, (such as [RFC6716]), FFV1 should not be used
   with insecure ciphers or cipher-modes that are vulnerable to known
   plaintext attacks.  Some of the header bits as well as the padding
   are easily predictable.

   Implementations of the FFV1 codec need to take appropriate security
   considerations into account, as outlined in [RFC4732].  It is
   extremely important for the decoder to be robust against malicious
   payloads.  Malicious payloads must not cause the decoder to overrun
   its allocated memory or to take an excessive amount of resources to
   decode.  The same applies to the encoder, even though problems in
   encoders are typically rarer.  Malicious video streams must not cause
   the encoder to misbehave because this would allow an attacker to
   attack transcoding gateways.  A frequent security problem in image
   and video codecs is also to not check for integer overflows in
   "Pixel" count computations, that is to allocate width * height
   without considering that the multiplication result may have
   overflowed the arithmetic types range.  The range coder could, if
   implemented naively, read one byte over the end.  The implementation
   must ensure that no read outside allocated and initialized memory
   occurs.

   The reference implementation [REFIMPL] contains no known buffer
   overflow or cases where a specially crafted packet or video segment
   could cause a significant increase in CPU load.

   The reference implementation [REFIMPL] was validated in the following
   conditions:

   *  Sending the decoder valid packets generated by the reference
      encoder and verifying that the decoder's output matches the
      encoder's input.

   *  Sending the decoder packets generated by the reference encoder and
      then subjected to random corruption.

   *  Sending the decoder random packets that are not FFV1.

   In all of the conditions above, the decoder and encoder was run
   inside the [VALGRIND] memory debugger as well as clangs address
   sanitizer [Address-Sanitizer], which track reads and writes to
   invalid memory regions as well as the use of uninitialized memory.
   There were no errors reported on any of the tested conditions.

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7.  Media Type Definition

   This registration is done using the template defined in [RFC6838] and
   following [RFC4855].

   Type name: video

   Subtype name: FFV1

   Required parameters: None.

   Optional parameters:

   This parameter is used to signal the capabilities of a receiver
   implementation.  This parameter MUST NOT be used for any other
   purpose.

   version: The version of the FFV1 encoding as defined by the section
   on version (#version).

   micro_version: The micro_version of the FFV1 encoding as defined by
   the section on micro_version (#micro-version).

   coder_type: The coder_type of the FFV1 encoding as defined by the
   section on coder_type (#coder-type).

   colorspace_type: The colorspace_type of the FFV1 encoding as defined
   by the section on colorspace_type (#colorspace-type).

   bits_per_raw_sample: The bits_per_raw_sample of the FFV1 encoding as
   defined by the section on bits_per_raw_sample (#bits-per-raw-sample).

   max-slices: The value of max-slices is an integer indicating the
   maximum count of slices with a frames of the FFV1 encoding.

   Encoding considerations:

   This media type is defined for encapsulation in several audiovisual
   container formats and contains binary data; see the section on
   "Mapping FFV1 into Containers" (#mapping-ffv1-into-containers).  This
   media type is framed binary data Section 4.8 of [RFC6838].

   Security considerations:

   See the "Security Considerations" section (#security-considerations)
   of this document.

   Interoperability considerations: None.

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   Published specification:

   [I-D.ietf-cellar-ffv1] and RFC XXXX.

   [RFC Editor: Upon publication as an RFC, please replace "XXXX" with
   the number assigned to this document and remove this note.]

   Applications which use this media type:

   Any application that requires the transport of lossless video can use
   this media type.  Some examples are, but not limited to screen
   recording, scientific imaging, and digital video preservation.

   Fragment identifier considerations: N/A.

   Additional information: None.

   Person & email address to contact for further information: Michael
   Niedermayer michael@niedermayer.cc (mailto:michael@niedermayer.cc)

   Intended usage: COMMON

   Restrictions on usage: None.

   Author: Dave Rice dave@dericed.com (mailto:dave@dericed.com)

   Change controller: IETF cellar working group delegated from the IESG.

8.  IANA Considerations

   The IANA is requested to register the following values:

   *  Media type registration as described in Media Type Definition
      (#media-type-definition).

9.  Appendixes

9.1.  Decoder implementation suggestions

9.1.1.  Multi-threading Support and Independence of Slices

   The FFV1 bitstream is parsable in two ways: in sequential order as
   described in this document or with the pre-analysis of the footer of
   each slice.  Each slice footer contains a slice_size field so the
   boundary of each slice is computable without having to parse the
   slice content.  That allows multi-threading as well as independence
   of slice content (a bitstream error in a slice header or slice
   content has no impact on the decoding of the other slices).

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   After having checked keyframe field, a decoder SHOULD parse
   slice_size fields, from slice_size of the last slice at the end of
   the "Frame" up to slice_size of the first slice at the beginning of
   the "Frame", before parsing slices, in order to have slices
   boundaries.  A decoder MAY fallback on sequential order e.g. in case
   of a corrupted "Frame" (frame size unknown, slice_size of slices not
   coherent...) or if there is no possibility of seeking into the
   stream.

10.  Changelog

   See https://github.com/FFmpeg/FFV1/commits/master
   (https://github.com/FFmpeg/FFV1/commits/master)

11.  Normative References

   [I-D.ietf-cellar-ffv1]
              Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video
              Coding Format Version 0, 1, and 3", Internet-Draft, draft-
              ietf-cellar-ffv1-09, 6 September 2019,
              <https://tools.ietf.org/html/draft-ietf-cellar-ffv1-09>.

   [ISO.15444-1.2016]
              International Organization for Standardization,
              "Information technology -- JPEG 2000 image coding system:
              Core coding system", October 2016.

   [ISO.9899.1990]
              International Organization for Standardization,
              "Programming languages - C", 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <https://www.rfc-editor.org/info/rfc4732>.

   [RFC4855]  Casner, S., "Media Type Registration of RTP Payload
              Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
              <https://www.rfc-editor.org/info/rfc4855>.

   [RFC6716]  Valin, JM., Vos, K., and T. Terriberry, "Definition of the
              Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
              September 2012, <https://www.rfc-editor.org/info/rfc6716>.

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   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

12.  Informative References

   [Address-Sanitizer]
              The Clang Team, "ASAN AddressSanitizer website", undated,
              <https://clang.llvm.org/docs/AddressSanitizer.html>.

   [AVI]      Microsoft, "AVI RIFF File Reference", undated,
              <https://msdn.microsoft.com/en-us/library/windows/desktop/
              dd318189%28v=vs.85%29.aspx>.

   [FFV1_V0]  Niedermayer, M., "Commit to mark FFV1 version 0 as non-
              experimental", April 2006,
              <https://git.videolan.org/?p=ffmpeg.git;a=commit;h=b548f2b
              91b701e1235608ac882ea6df915167c7e>.

   [FFV1_V1]  Niedermayer, M., "Commit to release FFV1 version 1", April
              2009,
              <https://git.videolan.org/?p=ffmpeg.git;a=commit;h=68f8d33
              becbd73b4d0aa277f472a6e8e72ea6849>.

   [FFV1_V3]  Niedermayer, M., "Commit to mark FFV1 version 3 as non-
              experimental", August 2013,
              <https://git.videolan.org/?p=ffmpeg.git;a=commit;h=abe76b8
              51c05eea8743f6c899cbe5f7409b0f301>.

   [HuffYUV]  Rudiak-Gould, B., "HuffYUV", December 2003,
              <https://web.archive.org/web/20040402121343/
              http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.

   [ISO.14495-1.1999]
              International Organization for Standardization,
              "Information technology -- Lossless and near-lossless
              compression of continuous-tone still images: Baseline",
              December 1999.

   [ISO.14496-10.2014]
              International Organization for Standardization,
              "Information technology -- Coding of audio-visual objects
              -- Part 10: Advanced Video Coding", September 2014.

   [ISO.14496-12.2015]
              International Organization for Standardization,

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              "Information technology -- Coding of audio-visual objects
              -- Part 12: ISO base media file format", December 2015.

   [Matroska] IETF, "Matroska", 2016,
              <https://datatracker.ietf.org/doc/draft-lhomme-cellar-
              matroska/>.

   [NUT]      Niedermayer, M., "NUT Open Container Format", December
              2013, <https://ffmpeg.org/~michael/nut.txt>.

   [range-coding]
              Nigel, G. and N. Martin, "Range encoding: an algorithm for
              removing redundancy from a digitised message.", July 1979.

   [REFIMPL]  Niedermayer, M., "The reference FFV1 implementation / the
              FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>.

   [VALGRIND] Valgrind Developers, "Valgrind website", undated,
              <https://valgrind.org/>.

   [YCbCr]    Wikipedia, "YCbCr", undated,
              <https://en.wikipedia.org/w/index.php?title=YCbCr>.

Authors' Addresses

   Michael Niedermayer

   Email: michael@niedermayer.cc

   Dave Rice

   Email: dave@dericed.com

   Jerome Martinez

   Email: jerome@mediaarea.net

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