Network Working Group H. Alvestrand
Internet-Draft A. Grange
Intended status: Informational Google
Expires: April 9, 2014 October 6, 2013
VP8 as RTCWEB Mandatory to Implement
draft-alvestrand-rtcweb-vp8-02
Abstract
This document recommends that the RTCWEB working group choose the VP8
specification as a mandatory to implement video codec for RTCWEB
implementations.
This document is not intended for publication as an RFC.
Requirements Language
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 RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 9, 2014.
Copyright Notice
Copyright (c) 2013 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
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements for an MTI codec . . . . . . . . . . . . . . . . 3
3. Specification status . . . . . . . . . . . . . . . . . . . . . 3
3.1. VP8 standardization status . . . . . . . . . . . . . . . . 3
4. Deployment status . . . . . . . . . . . . . . . . . . . . . . 4
5. Image quality evaluations . . . . . . . . . . . . . . . . . . 4
5.1. Objective evaluations . . . . . . . . . . . . . . . . . . 4
5.2. Subjective evaluations . . . . . . . . . . . . . . . . . . 5
6. Performance evaluation . . . . . . . . . . . . . . . . . . . . 5
6.1. Software . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.2. Hardware support . . . . . . . . . . . . . . . . . . . . . 6
6.3. Hardware performance . . . . . . . . . . . . . . . . . . . 6
7. IPR status . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
As described in [I-D.ietf-rtcweb-overview], successful interoperable
deployment of RTCWEB requires that implementations share a video
codec. Not requiring a video codec will mean that this decision is
left to processes outside the standards process, and risks the
spectre of fragmented deployment.
This memo argues that VP8 should be that codec.
2. Requirements for an MTI codec
As outlined by the presentation given at the IETF meeting at IETF 84
in Vancouver, it is unclear what the hard requirements for a video
codec are, but the items that it was suggested that proposals give
information on were:
o Image quality - comparative data was sought, but without defining
a baseline
o Performance - what resolutions / frame rates can be achieved in
software on some common systems
o Power consumption of hardware and/or software implementations
o Hardware support
o IPR status
This document lays out the available information in each category.
3. Specification status
VP8 is defined in [RFC6386], and its RTP payload is defined in
[I-D.ietf-payload-vp8] . There are no profiles; all decoders are
able to decode all valid media streams.
In the time since the original RFC publication, and indeed since the
first publication of the VP8 bitstream format, there have been no
changes to the decoder that broke bitstream compatibility.
3.1. VP8 standardization status
The VP8 codec has been proposed as a basis for standardization in
MPEG, in response to its Call for Proposals for a royalty-free video
codec. At its meeting in Vienna, Austria in July 2013, following the
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presentation of subjective and objective quality evaluation results,
and a focused discussion of possible IPR issues, MPEG passed a
resolution calling for the creation of a new project (Video Coding
for Browsers, or VCB), with the aim of producing a final DIS document
(FDIS) by July 2014. (MPEG output document w13648).
At the meeting of the US National Body of MPEG in October 013, the
USNB passed a resolution supporting this work, and expressing a
preference for "options that maintain a native VP8 mode" - that is,
no incompatible changes.
4. Deployment status
The VP8 codec has been extensively deployed in production services:
o Skype (now part of Microsoft) used the codec extensively in its
video conferencing software.
o Google Hangouts is now fully converted to using VP8 on the various
PC platforms. This platform now offers free videoconferencing in
HD quality to everyone.
o Google Remote Desktop uses VP8.
o Google Chromecast uses VP8, showing what can be achieved with
hardware decoding support.
o Both the Firefox and Chrome WebRTC implementations use VP8
exclusively.
5. Image quality evaluations
5.1. Objective evaluations
In tests carried out by Google on a set of ten sample video clips
containing typical video-conference content, VP8 outperformed the
x264 H.264 codec running the constrained baseline profile by on
average 37.2%. That is, at the same quality, measured by PSNR, VP8
produced 37.2% fewer bits on average than H.264. VP8 outperformed
H.264 on all ten of the test clips by between 19% and 64%. Both
codecs were configured in one-pass mode using settings conducive to
real-time operation, and the ten clips varied in size between 640x360
pixels and 1280x720 pixels.
The software and the clips are available via the WEBM project's GIT
repository:
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http://git.chromium.org/gitweb/?p=webm/vpx_codec_comparison.git
Note: Tests run by Ericsson have demonstrated that it is possible to
reduce the VP8 performance to be very close to that of baseline by
running in "fixed QP" mode - selecting a single QP value in order to
achieve a given bitrate. We believe this VP8 mode is an unrealistic
mode for production use, and not what we should be evaluating.
5.2. Subjective evaluations
As part of the process of submitting VP8 for evaluation in ISO/IEC
JTC1 SC29 WG11 (MPEG), the VP8 codec has been subjected to subjective
and objective quality evaluations; the input reports are in WG11
documents N13775 (Vienna, MPEG 105 meeting, subjective numbers for
VP8 performed by Vittorio Baroncini), M29364 (Incheon, subjective
comparision between VP8 and IVC) and M28182 (Geneva, MPEG 103
meeting), respectively.
These tests were performed at the laboratories of Vittori Baronici,
who is also a chair of the Testing subgroup of MPEG, and has
performed many of the subjective tests done as part of the HEVC
effort.
Together with the tests presented in document M29364, we also asked
Vittorio Baroncini to do a subjective evaluation of VP8 compared to
the AVC Baseline; the results of this evaluation are given in a
separate presentation.
In all these cases, VP8 performed adequately in subjective
evaluations; the numbers can be interpreted as showing that VP8 in
"realtime" mode performed better than the "anchors" on both tests,
but due to the amount of discussion occuring in the meetings about
whether the precise parameters chosen for the tests made it a "fair"
comparision, we will not state flatly that VP8 performed better than
the anchors (AVC Baseline and AVC High Profile, respectively), but we
will state flatly that there is no evicence that the anchors
performed significantly better than VP8.
6. Performance evaluation
6.1. Software
The current reference implementation is libvpx, developed in the WebM
project.
The encoding speed in software depends on the quality setting. On a
stock PC platform using an Intel Xeon CPU at 2.67 GHz, in a test
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using extremely difficult 720p material and encoding at a target data
rate of 2 Mbit/sec, VP8's encoding speed varied from 48.4 fps (at the
setting used in WebRTC today) to 96.2 fps (at the fastest setting),
using a single thread. This variation in encode speed is achieved by
changing the configuration of VP8 encoding tools in a deterministic
way to trade-off encoding speed with output quality.
On a stock PC platform using an Intel Xeon CPU with 8 cores at
2.27GHz, tests using difficult 720p material encoded at 2 Mbit/sec
show that using a single thread VP8 can decode at 200.50 fps (in
comparison H.264, baseline profile, achieves 107.95 fps), using four
threads VP8 decodes at 519.96 fps (H.264 achieves 363.73 fps), and
using sixteen threads VP8 decodes at 1,076.49 fps (H.264 achieves
807.11 fps).
6.2. Hardware support
NOTE: This section contains mostly information that was valid as of
October 2012. It will be updated.
As of October 2012, Google has licensed VP8 hardware accelerators to
over 50 chip manufacturers, and VP8 hardware IP cores have also been
made available by Imagination Technologies, Verisilicon and Chips &
Media. Furthermore, Google is aware of several 3rd party
implementations of VP8 decoders and encoders from the world's leading
semiconductor companies.
As of October 2012, more than a dozen chip manufacturers had
announced chips with 1080p VP8 support, including Samsung (Exynos 5),
NVIDIA (Tegra 3, Tegra 4), Marvell (Armada 1500), Broadcom
(BCM28150), Texas Instruments (OMAP54xx), Freescale (i.MX 6), ST-
Ericsson (NovaThor L9540), LG Electronics, Hisilicon (K3v2), Rockchip
(RK2918, RK3066), Nufront (NS115), Ziilabs (ZMS40) and Allwinner
(A10). Google estimates that a clear majority of leading mobile
chipsets in 2013 will contain VP8 hardware support. (Nvidia Tegra4
info added after October 2012).
The encoder chip produced by Quanta has allowed OEMs to integrate
hardware HD VP8 encoding into their video camera hardware; this chip
is available now. More suppliers have such a chip coming.
The ChromeCast device, which is selling in significant numbers in the
US, has VP8 hardware decode.
6.3. Hardware performance
Several of the aforementioned hardware implementations are based on
the WebM video hardware designs described at
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http://www.webmproject.org/hardware/. Performance figures include:
o Decode of 1080p video at 30 fps at less than 100 MHz clock
frequency
o Decoding more than ten simultaneous SD video streams on a single
chip
o Less than 25 milliwatts of power for 1080p decoding
o Encoding 1080p video at 30 fps at less than 220 MHz clock
frequency
o Less than 80 milliwatts of power for HD video encoding
Based on the Hantro G1 multiformat decoder implementation, the VP8
hardware decoder is 45% smaller in silicon area than the H.264 High
Profile decoder. VP8 also requires 18% less DRAM bandwidth than
H.264 as it does not use bidirectional inter prediction, allowing
significant reductions in the overall decoding system power
consumption.
7. IPR status
The IETF has a long tradition of preferring non-encumbered IPR
whenever possible, and especially to avoid IPR where using the
technoogy requires making agreements with and payments to third
parties as part of the cost of doing business. Among the reasons for
this tradition is that the requirement for IPR agreements severely
distorts the competitive landscape, and especially that it seriously
hampers people attempting to implement standards in open source, or
other business models where counting the number of installations or
users is difficult, expensive or simply impossible.
As of this moment (October 4, 2013), the following IPR disclosures
are filed in the IETF IPR database:
o https://datatracker.ietf.org/ipr/1571/ - by Google, declaring that
the technology is royalty-free.
o https://datatracker.ietf.org/ipr/2035/ - by Nokia, which does not
declare a royalty-free license.
The licensing terms for Google's IPR are available at
http://www.webmproject.org/license/additional/.
The Nokia IPR mentioned above includes IPR that has been asserted in
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ongoing litigation in Germany (Nokia v. HTC, District Court in
Mannheim, Germany. 7 O 201/12); on one of the patents, the court has
ruled that the phones in question (which support VP8) are not
infringing. As mentioned in
http://blog.webmproject.org/2013/08/good-news-from-germany.html?m=0;
the case is still ongoing.
The following companies have asserted that any IPR relevant to VP8
they might have is available for licensing by Google under a royalty
free license; the licensing terms are available at
http://www.webm-ccl.org/vp8/agreement/, as well as details on the
licensors:
o CIF Licensing LLC
o France Telecom
o Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung
e.V.
o Fujitsu Limited
o Koninklijke Philips Electronics N.V.
o LG Electronics Inc.
o Mitsubishi Electric Corporation
o MPEG LA, LLC
o NTT DOCOMO, INC
o Panasonic Corporation
o Samsung Electronics Co., Ltd.
o Siemens Corporation
The license can be executed on-line from the link given above.
8. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed if this document is
ever published as an RFC.
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9. Security Considerations
Codec definitions do not in themselves comprise security risks, as
long as there is no means of embedding active content in their
datastream. VP8 does not contain such active content.
Codec implementations have frequently been the cause of security
concerns. The reference implementation of VP8 has been extensively
tested by Google security experts, and is believed to be free from
exploitable vulnerabilities. There is a continuous program in place
to ensure that any vulnerabilities identified are repaired as quickly
as possible.
10. Acknowledgements
Several members of the Google VP8 team contributed to this memo.
In addition, we wish to thank the people from the X264 mailing list
who came forward with suggested improvements in the codec settings
for the objective performance evaluations, Bo Burmann who re-ran the
tests entirely independently of Google, Mohammed Raad and Lazar
Bivolarski who prepared the materials for the subjective evaluation
tests and Vittorio Baronici who performed them, and all the countless
members of the RTCWEB working group who have debated extensively the
matter of mandatory to implement video codecs.
11. References
11.1. Normative References
[I-D.ietf-payload-vp8]
Westin, P., Lundin, H., Glover, M., Uberti, J., and F.
Galligan, "RTP Payload Format for VP8 Video",
draft-ietf-payload-vp8-09 (work in progress), July 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6386] Bankoski, J., Koleszar, J., Quillio, L., Salonen, J.,
Wilkins, P., and Y. Xu, "VP8 Data Format and Decoding
Guide", RFC 6386, November 2011.
11.2. Informative References
[I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Brower-
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based Applications", draft-ietf-rtcweb-overview-08 (work
in progress), September 2013.
Authors' Addresses
Harald Alvestrand
Google
Kungsbron 2
Stockholm, 11122
Sweden
Email: harald@alvestrand.no
Adrian Grange
Google
1950 Charleston Road
Mountain View, CA 94043
USA
Phone:
Fax:
Email: agrange@google.com
URI:
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