Applying PVQ Outside Daala
draft-cho-netvc-applypvq-02

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NETVC (Internet Video Codec)                                      Y. Cho
Internet-Draft                                       Mozilla Corporation
Intended status: Informational                          October 31, 2016
Expires: May 4, 2017

                       Applying PVQ Outside Daala
                      draft-cho-netvc-applypvq-02

Abstract

   This document describes the Perceptual Vector Quantization (PVQ)
   outside of the Daala video codec, where PVQ was originally developed.
   It discusses the issues arising while integrating PVQ into a
   traditional video codec, AV1.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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Table of Contents

   1.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Integration of PVQ into non-Daala codec, AV1  . . . . . . . .   3
     2.1.  Signaling Skip for Partition and Transform Block  . . . .   4
     2.2.  Issues  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Performance of PVQ in AV1 . . . . . . . . . . . . . . . . . .   5
     3.1.  Coding Gain . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Speed . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Development Repository  . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Informative References  . . . . . . . . . . . . . . . . .   9
     8.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Background

   Perceptual Vector Quantization (PVQ)
   [Perceptual-VQ][I-D.valin-netvc-pvq] has been proposed as a
   quantization and coefficient coding tool for an internet video codec.
   PVQ was originally developed for Daala video codec [1] [PVQ-demo],
   which does a gain-shape coding of transform coefficients instead of
   more traditional scalar quantization.  (The original abbreviation of
   PVQ, "Pyramid Vector Quantizer", as in [I-D.valin-netvc-pvq] is now
   commonly expanded as "Perceptual Vector Quantization".)

   The most distinguishing idea of PVQ is the way it references a
   predictor.  With PVQ, we do not subtract the predictor from the input
   to produce a residual, which is then transformed and coded.  Both the
   predictor and the input are transformed into the frequency domain.
   Then, PVQ applies a reflection to both the predictor and the input
   such that the prediction vector lies on one of the coordinate axes,
   and codes the angle between them.  By not subtracting the predictor
   from the input, the gain of the predictor can be preserved and is
   explicitly coded, which is one of the benefits of PVQ.  Since DC is
   not quantized by PVQ, the gain can be viewed as the amount of
   contrast in an image, which is an important perceptual parameter.

   Also, an input block of transform coefficients is split into
   frequency bands based on their spatial orientation and scale.  Then,
   each band is quantized by PVQ separately.  The 'gain' of a band
   indicates the amount of contrast in the corresponding orientation and
   scale.  It is simply the L2 norm of the band.  The gain is non-
   linearly companded and then scalar quantized and coded.  The

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