Internet DRAFT - draft-ietf-netvc-requirements
draft-ietf-netvc-requirements
Network Working Group A. Filippov
Internet Draft Huawei Technologies
Intended status: Informational A. Norkin
Netflix
J.R. Alvarez
Huawei Technologies
Expires: April 20, 2020 November 21, 2019
Video Codec Requirements and Evaluation Methodology
draft-ietf-netvc-requirements-10.txt
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Abstract
This document provides requirements for a video codec designed
mainly for use over the Internet. In addition, this document
describes an evaluation methodology needed for measuring the
compression efficiency to ensure whether the stated requirements are
fulfilled or not.
Table of Contents
1. Introduction...................................................3
2. Definitions and abbreviations used in this document............4
3. Applications...................................................6
3.1. Internet Video Streaming..................................6
3.2. Internet Protocol Television (IPTV).......................8
3.3. Video conferencing.......................................10
3.4. Video sharing............................................10
3.5. Screencasting............................................11
3.6. Game streaming...........................................13
3.7. Video monitoring / surveillance..........................13
4. Requirements..................................................14
4.1. General requirements.....................................14
4.2. Basic requirements.......................................16
4.2.1. Input source formats:...............................16
4.2.2. Coding delay:.......................................17
4.2.3. Complexity:.........................................17
4.2.4. Scalability:........................................18
4.2.5. Error resilience:...................................18
4.3. Optional requirements....................................18
4.3.1. Input source formats................................18
4.3.2. Scalability:........................................18
4.3.3. Complexity:.........................................19
4.3.4. Coding efficiency...................................19
5. Evaluation methodology........................................19
6. Security Considerations.......................................22
7. IANA Considerations...........................................22
8. References....................................................22
8.1. Normative References.....................................22
8.2. Informative References...................................23
9. Acknowledgments...............................................24
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1. Introduction
In this document, the requirements for a video codec designed mainly
for use over the Internet are presented. The requirements encompass
a wide range of applications that use data transmission over the
Internet including Internet video streaming, IPTV, peer-to-peer
video conferencing, video sharing, screencasting, game streaming and
video monitoring / surveillance. For each application, typical
resolutions, frame-rates and picture access modes are presented.
Specific requirements related to data transmission over packet-loss
networks are considered as well. In this document, when we discuss
data protection techniques we only refer to methods designed and
implemented to protect data inside the video codec since there are
many existing techniques that protect generic data transmitted over
networks with packet losses. From the theoretical point of view,
both packet-loss and bit-error robustness can be beneficial for
video codecs. In practice, packet losses are a more significant
problem than bit corruption in IP networks. It is worth noting that
there is an evident interdependence between possible amount of delay
and the necessity of error robust video streams:
o If an amount of delay is not crucial for an application, then
reliable transport protocols such as TCP that retransmits
undelivered packets can be used to guarantee correct decoding of
transmitted data.
o If the amount of delay must be kept low, then either data
transmission should be error free (e.g., by using managed
networks) or compressed video stream should be error resilient.
Thus, error resilience can be useful for delay-critical applications
to provide low delay in packet-loss environment.
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2. Definitions and abbreviations used in this document
+------------------+-----------------------------------------------+
| Term | Meaning |
+------------------+-----------------------------------------------+
| High dynamic | is a set of techniques that allow a greater |
| range imaging | dynamic range of exposures or values (i.e., |
| | a wide range of values between light and dark |
| | areas) than normal digital imaging techniques.|
| | The intention is to accurately represent the |
| | wide range of intensity levels found in such |
| | examples as exterior scenes that include |
| | light-colored items struck by direct sunlight |
| | and areas of deep shadow [7]. |
| | |
| Random access | is the period of time between two closest |
| period | independently decodable frames (pictures). |
| | |
| RD-point | A point in a two dimensional rate-distortion |
| | space where the values of bitrate and quality |
| | metric are used as x- and y-coordinates, |
| | respectively |
| | |
| Visually | is a form or manner of lossy compression |
| lossless | where the data that are lost after the file |
| compression | is compressed and decompressed is not |
| | detectable to the eye; the compressed data |
| | appearing identical to the uncompressed |
| | data [8]. |
| | |
| Wide color gamut | is a certain complete color subset (e.g., |
| | considered in ITU-R BT.2020) that supports a |
| | wider range of colors (i.e., an extended range|
| | of colors that can be generated by a specific |
| | input or output device such as a video camera,|
| | monitor or printer and can be interpreted by |
| | a color model) than conventional color gamuts |
| | (e.g., considered in ITU-R BT.601 or BT.709). |
+------------------+-----------------------------------------------+
Table 1. Definitions used in the text of this document
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+--------------+---------------------------------------------------+
| Abbreviation | Meaning |
+--------------+---------------------------------------------------+
| AI | All-Intra (each picture is intra-coded) |
| BD-Rate | Bjontegaard Delta Rate |
| FIZD | just the First picture is Intra-coded, Zero |
| | structural Delay |
| GOP | Group of Picture |
| HBR | High Bitrate Range |
| HDR | High Dynamic Range |
| HRD | Hypothetical Reference Decoder |
| IPTV | Internet Protocol Television |
| LBR | Low Bitrate Range |
| MBR | Medium Bitrate Range |
| MOS | Mean Opinion Score |
| MS-SSIM | Multi-Scale Structural Similarity quality index |
| PAM | Picture Access Mode |
| PSNR | Peak Signal-to-Noise Ratio |
| QoS | Quality of Service |
| QP | Quantization Parameter |
| RA | Random Access |
| RAP | Random Access Period |
| RD | Rate-Distortion |
| SEI | Supplemental Enhancement Information |
| UGC | User-Generated Content |
| VDI | Virtual Desktop Infrastructure |
| VUI | Video Usability Information |
| WCG | Wide Color Gamut |
+--------------+---------------------------------------------------+
Table 2. Abbreviations used in the text of this document
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3. Applications
In this chapter, an overview of video codec applications that are
currently available on the Internet market is presented. It is worth
noting that there are different use cases for each application that
define a target platform, and hence there are different types of
communication channels involved (e.g., wired or wireless channels)
that are characterized by different quality of service as well as
bandwidth; for instance, wired channels are considerably more error-
free than wireless channels and therefore require different QoS
approaches. The target platform, the channel bandwidth and the
channel quality determine resolutions, frame-rates and quality or
bit-rates for video streams to be encoded or decoded. By default,
color format YCbCr 4:2:0 is assumed for the application scenarios
listed below.
3.1. Internet Video Streaming
Typical content for this application is movies, TV-series and shows,
and animation. Internet video streaming uses a variety of client
devices and has to operate under changing network conditions. For
this reason, an adaptive streaming model has been widely adopted.
Video material is encoded at different quality levels and different
resolutions, which are then chosen by a client depending on its
capabilities and current network bandwidth. An example combination
of resolutions and bitrates is shown in Table 3.
A video encoding pipeline in on-demand Internet video streaming
typically operates as follows:
o Video is encoded in the cloud by software encoders.
o Source video is split into chunks, each of which is encoded
separately, in parallel.
o Closed-GOP encoding with 2-5 second intra-picture intervals (or
more) is used.
o Encoding is perceptually optimized. Perceptual quality is
important and should be considered during the codec development.
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+----------------------+-------------------------+-----------------+
| Resolution * | Frame-rate, fps | PAM |
+----------------------+-------------------------+-----------------+
+----------------------+-------------------------+-----------------+
| 4K, 3840x2160 | 24/1.001, 24, 25, | RA |
+----------------------+ +-----------------+
| 2K (1080p), 1920x1080| 30/1.001, 30, 50, | RA |
+----------------------+ +-----------------+
| 1080i, 1920x1080* | 60/1.001, 60, 100, | RA |
+----------------------+ +-----------------+
| 720p, 1280x720 | 120/1.001, 120 | RA |
+----------------------+ +-----------------+
| 576p (EDTV), 720x576 | The set of frame-rates | RA |
+----------------------+ +-----------------+
| 576i (SDTV), 720x576*| presented in this table | RA |
+----------------------+ +-----------------+
| 480p (EDTV), 720x480 | is taken from Table 2 | RA |
+----------------------+ +-----------------+
| 480i (SDTV), 720x480*| in [1] | RA |
+----------------------+ +-----------------+
| 512x384 | | RA |
+----------------------+ +-----------------+
| QVGA, 320x240 | | RA |
+----------------------+-------------------------+-----------------+
Table 3. Internet Video Streaming: typical values of resolutions,
frame-rates, and RAPs
NB *: Interlaced content can be handled at the higher system level
and not necessarily by using specialized video coding tools. It is
included in this table only for the sake of completeness as most
video content today is in the progressive format.
Characteristics and requirements of this application scenario are as
follows:
o High encoder complexity (up to 10x and more) can be tolerated
since encoding happens once and in parallel for different
segments.
o Decoding complexity should be kept at reasonable levels to enable
efficient decoder implementation.
o Support and efficient encoding of a wide range of content types
and formats is required:
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. High Dynamic Range (HDR), Wide Color Gamut (WCG), high
resolution (currently, up to 4K), high frame-rate content are
important use cases, the codec should be able to encode such
content efficiently.
. Coding efficiency improvement at both lower and higher
resolutions is important since low resolutions are used when
streaming in low bandwidth conditions.
. Improvement on both "easy" and "difficult" content in terms
of compression efficiency at the same quality level
contributes to the overall bitrate/storage savings.
. Film grain (and sometimes other types of noise) is often
present in the streaming movie-type content and is usually a
part of the creative intent.
o Significant improvements in compression efficiency between
generations of video standards are desirable since this scenario
typically assumes long-term support of legacy video codecs.
o Random access points are inserted frequently (one per 2-5
seconds) to enable switching between resolutions and fast-forward
playback.
o Elementary stream should have a model that allows easy parsing
and identification of the sample components.
o Middle QP values are normally used in streaming, this is also the
range where compression efficiency is important for this
scenario.
o Scalability or other forms of supporting multiple quality
representations are beneficial if they do not incur significant
bitrate overhead and if mandated in the first version.
3.2. Internet Protocol Television (IPTV)
This is a service for delivering television content over IP-based
networks. IPTV may be classified into two main groups based on the
type of delivery, as follows:
o unicast (e.g., for video on demand), where delay is not crucial;
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o multicast/broadcast (e.g., for transmitting news) where zapping,
i.e. stream changing, delay is important.
In the IPTV scenario, traffic is transmitted over managed (QoS-
based) networks. Typical content used in this application is news,
movies, cartoons, series, TV shows, etc. One important requirement
for both groups is Random access to pictures, i.e. random access
period (RAP) should be kept small enough (approximately, 1-5
seconds). Optional requirements are as follows:
o Temporal (frame-rate) scalability;
o Resolution and quality (SNR) scalability.
For this application, typical values of resolutions, frame-rates,
and RAPs are presented in Table 4.
+----------------------+-------------------------+-----------------+
| Resolution * | Frame-rate, fps | PAM |
+----------------------+-------------------------+-----------------+
+----------------------+-------------------------+-----------------+
| 2160p (4K),3840x2160 | 24/1.001, 24, 25, | RA |
+----------------------+ +-----------------+
| 1080p, 1920x1080 | 30/1.001, 30, 50, | RA |
+----------------------+ +-----------------+
| 1080i, 1920x1080* | 60/1.001, 60, 100, | RA |
+----------------------+ +-----------------+
| 720p, 1280x720 | 120/1.001, 120 | RA |
+----------------------+ +-----------------+
| 576p (EDTV), 720x576 | The set of frame-rates | RA |
+----------------------+ +-----------------+
| 576i (SDTV), 720x576*| presented in this table | RA |
+----------------------+ +-----------------+
| 480p (EDTV), 720x480 | is taken from Table 2 | RA |
+----------------------+ +-----------------+
| 480i (SDTV), 720x480*| in [1] | RA |
+----------------------+-------------------------+-----------------+
Table 4. IPTV: typical values of resolutions, frame-rates, and RAPs
NB *: Interlaced content can be handled at the higher system level
and not necessarily by using specialized video coding tools. It is
included in this table only for the sake of completeness as most
video content today is in progressive format.
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3.3. Video conferencing
This is a form of video connection over the Internet. This form
allows users to establish connections to two or more people by two-
way video and audio transmission for communication in real-time. For
this application, both stationary and mobile devices can be used.
The main requirements are as follows:
o Delay should be kept as low as possible (the preferable and
maximum end-to-end delay values should be less than 100 ms [9]
and 320 ms [2], respectively);
o Temporal (frame-rate) scalability;
o Error robustness.
Support of resolution and quality (SNR) scalability is highly
desirable. For this application, typical values of resolutions,
frame-rates, and RAPs are presented in Table 5.
+----------------------+-------------------------+----------------+
| Resolution | Frame-rate, fps | PAM |
+----------------------+-------------------------+----------------+
+----------------------+-------------------------+----------------+
| 1080p, 1920x1080 | 15, 30 | FIZD |
+----------------------+-------------------------+----------------+
| 720p, 1280x720 | 30, 60 | FIZD |
+----------------------+-------------------------+----------------+
| 4CIF, 704x576 | 30, 60 | FIZD |
+----------------------+-------------------------+----------------+
| 4SIF, 704x480 | 30, 60 | FIZD |
+----------------------+-------------------------+----------------+
| VGA, 640x480 | 30, 60 | FIZD |
+----------------------+-------------------------+----------------+
| 360p, 640x360 | 30, 60 | FIZD |
+----------------------+-------------------------+----------------+
Table 5. Video conferencing: typical values of resolutions, frame-
rates, and RAPs
3.4. Video sharing
This is a service that allows people to upload and share video data
(using live streaming or not) and to watch them. It is also known as
video hosting. A typical User-generated Content (UGC) scenario for
this application is to capture video using mobile cameras such as
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GoPro or cameras integrated into smartphones (amateur video). The
main requirements are as follows:
o Random access to pictures for downloaded video data;
o Temporal (frame-rate) scalability;
o Error robustness.
Support of resolution and quality (SNR) scalability is highly
desirable. For this application, typical values of resolutions,
frame-rates, and RAPs are presented in Table 6.
+----------------------+-------------------------+----------------+
| Resolution | Frame-rate, fps | PAM |
+----------------------+-------------------------+----------------+
+----------------------+-------------------------+----------------+
| 2160p (4K),3840x2160 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
| 1440p (2K),2560x1440 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
| 1080p, 1920x1080 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
| 720p, 1280x720 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
| 480p, 854x480 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
| 360p, 640x360 | 24, 25, 30, 48, 50, 60 | RA |
+----------------------+-------------------------+----------------+
Table 6. Video sharing: typical values of resolutions, frame-rates
[10], and RAPs
3.5. Screencasting
This is a service that allows users to record and distribute
computer desktop screen output. This service requires efficient
compression of computer-generated content with high visual quality
up to visually and mathematically (numerically) lossless [11].
Currently, this application includes business presentations
(powerpoint, word documents, email messages, etc.), animation
(cartoons), gaming content, data visualization, i.e. such type of
content that is characterized by fast motion, rotation, smooth
shade, 3D effect, highly saturated colors with full resolution,
clear textures and sharp edges with distinct colors [11]), virtual
desktop infrastructure (VDI), screen/desktop sharing and
collaboration, supervisory control and data acquisition (SCADA)
display, automotive/navigation display, cloud gaming, factory
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automation display, wireless display, display wall, digital
operating room (DiOR), etc. For this application, an important
requirement is the support of low-delay configurations with zero
structural delay, a wide range of video formats (e.g., RGB) in
addition to YCbCr 4:2:0 and YCbCr 4:4:4 [11]. For this application,
typical values of resolutions, frame-rates, and RAPs are presented
in Table 7.
+----------------------+-------------------------+----------------+
| Resolution | Frame-rate, fps | PAM |
+----------------------+-------------------------+----------------+
+----------------------+-------------------------+----------------+
| Input color format: RGB 4:4:4 |
+----------------------+-------------------------+----------------+
| 5k, 5120x2880 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| 4k, 3840x2160 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| WQXGA, 2560x1600 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| WUXGA, 1920x1200 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| WSXGA+, 1680x1050 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| WXGA, 1280x800 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| XGA, 1024x768 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| SVGA, 800x600 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| VGA, 640x480 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| Input color format: YCbCr 4:4:4 |
+----------------------+-------------------------+----------------+
| 5k, 5120x2880 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| 4k, 3840x2160 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| 1440p (2K), 2560x1440| 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| 1080p, 1920x1080 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
| 720p, 1280x720 | 15, 30, 60 | AI, RA, FIZD |
+----------------------+-------------------------+----------------+
Table 7. Screencasting for RGB and YCbCr 4:4:4 format: typical
values of resolutions, frame-rates, and RAPs
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3.6. Game streaming
This is a service that provides game content over the Internet to
different local devices such as notebooks, gaming tablets, etc. In
this category of applications, server renders 3D games in cloud
server, and streams the game to any device with a wired or wireless
broadband connection [12]. There are low latency requirements for
transmitting user interactions and receiving game data in less than
a turn-around delay of 100 ms. This allows anyone to play (or
resume) full featured games from anywhere in the Internet [12]. An
example of this application is Nvidia Grid [12]. Another category
application is broadcast of video games played by people over the
Internet in real time or for later viewing [12]. There are many
companies such as Twitch, YY in China enable game broadcasting [12].
Games typically contain a lot of sharp edges and large motion [12].
The main requirements are as follows:
o Random access to pictures for game broadcasting;
o Temporal (frame-rate) scalability;
o Error robustness.
Support of resolution and quality (SNR) scalability is highly
desirable. For this application, typical values of resolutions,
frame-rates, and RAPs are similar to ones presented in Table 5.
3.7. Video monitoring / surveillance
This is a type of live broadcasting over IP-based networks. Video
streams are sent to many receivers at the same time. A new receiver
may connect to the stream at an arbitrary moment, so random access
period should be kept small enough (approximately, ~1-5 seconds).
Data are transmitted publicly in the case of video monitoring and
privately in the case of video surveillance, respectively. For IP-
cameras that have to capture, process and encode video data,
complexity including computational and hardware complexity as well
as memory bandwidth should be kept low to allow real-time
processing. In addition, support of high dynamic range and a
monochrome mode (e.g., for infrared cameras) as well as resolution
and quality (SNR) scalability is an essential requirement for video
surveillance. In some use-cases, high video signal fidelity is
required even after lossy compression. Typical values of
resolutions, frame-rates, and RAPs for video monitoring /
surveillance applications are presented in Table 8.
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+----------------------+-------------------------+-----------------+
| Resolution | Frame-rate, fps | PAM |
+----------------------+-------------------------+-----------------+
+----------------------+-------------------------+-----------------+
| 2160p (4K),3840x2160 | 12, 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
| 5Mpixels, 2560x1920 | 12, 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
| 1080p, 1920x1080 | 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
| 1.3Mpixels, 1280x960 | 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
| 720p, 1280x720 | 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
| SVGA, 800x600 | 25, 30 | RA, FIZD |
+----------------------+-------------------------+-----------------+
Table 8. Video monitoring / surveillance: typical values of
resolutions, frame-rates, and RAPs
4. Requirements
Taking the requirements discussed above for specific video
applications, this chapter proposes requirements for an internet
video codec.
4.1. General requirements
4.1.1. The most basic requirement is coding efficiency, i.e.
compression performance on both "easy" and "difficult" content for
applications and use cases in Section 2. The codec should provide
higher coding efficiency over state-of-the-art video codecs such as
HEVC/H.265 and VP9, at least by 25% in accordance with the
methodology described in Section 4.1 of this document. For higher
resolutions, the coding efficiency improvements are expected to be
higher than for lower resolutions.
4.1.2. Good quality specification and well-defined profiles and
levels are required to enable device interoperability and facilitate
decoder implementations. A profile consists of a subset of entire
bitstream syntax elements and consequently it also defines the
necessary tools for decoding a conforming bitstream of that profile.
A level imposes a set of numerical limits to the values of some
syntax elements. An example of codec levels to be supported is
presented in Table 9. An actual level definition should include
constraints on features that impact the decoder complexity. For
example, these features might be as follows: maximum bit-rate, line
buffer size, memory usage, etc.
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+------------------------------------------------------------------+
| Level | Example picture resolution at highest frame rate |
+-------------+----------------------------------------------------+
| | 128x96(12,288*)@30.0 |
| 1 | 176x144(25,344*)@15.0 |
+-------------+----------------------------------------------------+
| 2 | 352x288(101,376*)@30.0 |
+-------------+----------------------------------------------------+
| | 352x288(101,376*)@60.0 |
| 3 | 640x360(230,400*)@30.0 |
+-------------+----------------------------------------------------+
| | 640x360(230,400*)@60.0 |
| 4 | 960x540(518,400*)@30.0 |
+-------------+----------------------------------------------------+
| | 720x576(414,720*)@75.0 |
| 5 | 960x540(518,400*)@60.0 |
| | 1280x720(921,600*)@30.0 |
+-------------+----------------------------------------------------+
| | 1,280x720(921,600*)@68.0 |
| 6 | 2,048x1,080(2,211,840*)@30.0 |
+-------------+----------------------------------------------------+
| | 1,280x720(921,600*)@120.0 |
| 7 | 2,048x1,080(2,211,840*)@60.0 |
+-------------+----------------------------------------------------+
| | 1,920x1,080(2,073,600*)@120.0 |
| 8 | 3,840x2,160(8,294,400*)@30.0 |
| | 4,096x2,160(8,847,360*)@30.0 |
+-------------+----------------------------------------------------+
| | 1,920x1,080(2,073,600*)@250.0 |
| 9 | 4,096x2,160(8,847,360*)@60.0 |
+-------------+----------------------------------------------------+
| | 1,920x1,080(2,073,600*)@300.0 |
| 10 | 4,096x2,160(8,847,360*)@120.0 |
+-------------+----------------------------------------------------+
| | 3,840x2,160(8,294,400*)@120.0 |
| 11 | 8,192x4,320(35,389,440*)@30.0 |
+-------------+----------------------------------------------------+
| | 3,840x2,160(8,294,400*)@250.0 |
| 12 | 8,192x4,320(35,389,440*)@60.0 |
+-------------+----------------------------------------------------+
| | 3,840x2,160(8,294,400*)@300.0 |
| 13 | 8,192x4,320(35,389,440*)@120.0 |
+-------------+----------------------------------------------------+
Table 9. Codec levels
NB *: The quantities of pixels are presented for such applications
where a picture can have an arbitrary size (e.g., screencasting)
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4.1.3. Bitstream syntax should allow extensibility and backward
compatibility. New features can be supported easily by using
metadata (e.g., such as SEI messages, VUI, headers) without
affecting the bitstream compatibility with legacy decoders. A newer
version of the decoder shall be able to play bitstreams of an older
version of the same or lower profile and level.
4.1.4. A bitstream should have a model that allows easy parsing and
identification of the sample components (such as ISO/IEC14496-10,
Annex B or ISO/IEC 14496-15). In particular, information needed for
packet handling (e.g., frame type) should not require parsing
anything below the header level.
4.1.5. Perceptual quality tools (such as adaptive QP and
quantization matrices) should be supported by the codec bit-stream.
4.1.6. The codec specification shall define a buffer model such as
hypothetical reference decoder (HRD).
4.1.7. Specifications providing integration with system and delivery
layers should be developed.
4.2. Basic requirements
4.2.1. Input source formats:
o Bit depth: 8- and 10-bits (up to 12-bits for a high profile) per
color component;
o Color sampling formats:
. YCbCr 4:2:0;
. YCbCr 4:4:4, YCbCr 4:2:2 and YCbCr 4:0:0 (preferably in
different profile(s)).
o For profiles with bit depth of 10 bits per sample or higher,
support of high dynamic range and wide color gamut.
o Support of arbitrary resolution according to the level
constraints for such applications where a picture can have an
arbitrary size (e.g., in screencasting).
o Exemplary input source formats for codec profiles are shown in
Table 10.
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+---------+-----------------+-----------------------------------------+
| Profile | Bit-depths per | Color sampling formats |
| | color component | |
+---------+-----------------+-----------------------------------------+
| 1 | 8 and 10 | 4:0:0 and 4:2:0 |
+---------+-----------------+-----------------------------------------+
| 2 | 8 and 10 | 4:0:0, 4:2:0 and 4:4:4 |
+---------+-----------------+-----------------------------------------+
| 3 | 8, 10 and 12 | 4:0:0, 4:2:0, 4:2:2 and 4:4:4 |
+---------+-----------------+-----------------------------------------+
Table 10. Exemplary input source formats for codec profiles
4.2.2. Coding delay:
o Support of configurations with zero structural delay also
referred to as "low-delay" configurations.
. Note 1: end-to-end delay should be up to 320 ms [2] but its
preferable value should be less than 100 ms [9]
o Support of efficient random access point encoding (such as intra
coding and resetting of context variables) as well as efficient
switching between multiple quality representations.
o Support of configurations with non-zero structural delay (such as
out-of-order or multi-pass encoding) for applications without
low-delay requirements if such configurations provide additional
compression efficiency improvements.
4.2.3. Complexity:
o Feasible real-time implementation of both an encoder and a
decoder supporting a chosen subset of tools for hardware and
software implementation on a wide range of state-of-the-art
platforms. The real-time encoder tools subset should provide
meaningful improvement in compression efficiency at reasonable
complexity of hardware and software encoder implementations as
compared to real-time implementations of state-of-the-art video
compression technologies such as HEVC/H.265 and VP9.
o High-complexity software encoder implementations used by offline
encoding applications can have 10x or more complexity increase
compared to state-of-the-art video compression technologies such
as HEVC/H.265 and VP9.
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4.2.4. Scalability:
o Temporal (frame-rate) scalability should be supported.
4.2.5. Error resilience:
o Error resilience tools that are complementary to the error
protection mechanisms implemented on transport level should be
supported.
o The codec should support mechanisms that facilitate packetization
of a bitstream for common network protocols.
o Packetization mechanisms should enable frame-level error recovery
by means of retransmission or error concealment.
o The codec should support effective mechanisms for allowing
decoding and reconstruction of significant parts of pictures in
the event that parts of the picture data are lost in
transmission.
o The bitstream specification shall support independently decodable
sub-frame units similar to slices or independent tiles. It shall
be possible for the encoder to restrict the bit-stream to allow
parsing of the bit-stream after a packet-loss and to communicate
it to the decoder.
4.3. Optional requirements
4.3.1. Input source formats
o Bit depth: up to 16-bits per color component.
o Color sampling formats: RGB 4:4:4.
o Auxiliary channel (e.g., alpha channel) support.
4.3.2. Scalability:
o Resolution and quality (SNR) scalability that provide low
compression efficiency penalty (up to 5% of BD-rate [13] increase
per layer with reasonable increase of both computational and
hardware complexity) can be supported in the main profile of the
codec being developed by the NETVC WG. Otherwise, a separate
profile is needed to support these types of scalability.
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o Computational complexity scalability(i.e. computational
complexity is decreasing along with degrading picture quality) is
desirable.
4.3.3. Complexity:
Tools that enable parallel processing (e.g., slices, tiles, wave
front propagation processing) at both encoder and decoder sides are
highly desirable for many applications.
o High-level multi-core parallelism: encoder and decoder operation,
especially entropy encoding and decoding, should allow multiple
frames or sub-frame regions (e.g. 1D slices, 2D tiles, or
partitions) to be processed concurrently, either independently or
with deterministic dependencies that can be efficiently pipelined
o Low-level instruction set parallelism: favor algorithms that are
SIMD/GPU friendly over inherently serial algorithms
4.3.4. Coding efficiency
Compression efficiency on noisy content, content with film grain,
computer generated content, and low resolution materials is
desirable.
5. Evaluation methodology
As shown in Fig.1, compression performance testing is performed in 3
overlapped ranges that encompass 10 different bitrate values:
o Low bitrate range (LBR) is the range that contains the 4 lowest
bitrates of the 10 specified bitrates (1 of the 4 bitrate values
is shared with the neighboring range);
o Medium bitrate range (MBR) is the range that contains the 4
medium bitrates of the 10 specified bitrates (2 of the 4 bitrate
values are shared with the neighboring ranges);
o High bitrate range (HBR) is the range that contains the 4 highest
bitrates of the 10 specified bitrates (1 of the 4 bitrate values
is shared with the neighboring range).
Initially, for the codec selected as a reference one (e.g., HEVC or
VP9), a set of 10 QP (quantization parameter) values should be
specified in [14] and corresponding quality values should be
calculated. In Fig.1, QP and quality values are denoted as QP0, QP1,
QP2,..., QP8, QP9 and Q0, Q1, Q2,..., Q8, Q9, respectively. To
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guarantee the overlaps of quality levels between the bitrate ranges
of the reference and tested codecs, a quality alignment procedure
should be performed for each range's outermost (left- and rightmost)
quality levels Qk of the reference codec (i.e. for Q0, Q3, Q6, and
Q9) and the quality levels Q'k (i.e. Q'0, Q'3, Q'6, and Q'9) of the
tested codec. Thus, these quality levels Q'k and, hence, the
corresponding QP value QP'k (i.e. QP'0, QP'3, QP'6, and QP'9) of the
tested codec should be selected using the following formulas:
Q'k = min { abs(Q'i - Qk) },
i in R
QP'k = argmin { abs(Q'i(QP'i) - Qk(QPk)) },
i in R
where R is the range of the QP indexes of the tested codec, i.e. the
candidate Internet video codec. The inner quality levels (i.e. Q'1,
Q'2, Q'4, Q'5, Q'7, and Q'8) as well as their corresponding QP
values of each range (i.e. QP'1, QP'2, QP'4, QP'5, QP'7, and QP'8)
should be as equidistantly spaced as possible between the left- and
rightmost quality levels without explicitly mapping their values
using the above described procedure.
QP'9 QP'8 QP'7 QP'6 QP'5 QP'4 QP'3 QP'2 QP'1 QP'0 <+-----
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ | Tested
| | | | | | | | | | | codec
Q'0 Q'1 Q'2 Q'3 Q'4 Q'5 Q'6 Q'7 Q'8 Q'9 <+-----
^ ^ ^ ^
| | | |
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 <+-----
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ | Reference
| | | | | | | | | | | codec
QP9 QP8 QP7 QP6 QP5 QP4 QP3 QP2 QP1 QP0 <+-----
+----------------+--------------+--------------+--------->
^ ^ ^ ^ Bit-rate
|-------LBR------| |-----HBR------|
^ ^
|------MBR-----|
Figure 1 Quality/QP alignment for compression performance evaluation
Since the QP mapping results may vary for different sequences,
eventually, this quality alignment procedure needs to be separately
performed for each quality assessment index and each sequence used
for codec performance evaluation to fulfill the above described
requirements.
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To assess the quality of output (decoded) sequences, two indexes,
PSNR [3] and MS-SSIM [3,15] are separately computed. In the case of
the YCbCr color format, PSNR should be calculated for each color
plane whereas MS-SSIM is calculated for luma channel only. In the
case of the RGB color format, both metrics are computed for R, G and
B channels. Thus, for each sequence, 30 RD-points for PSNR (i.e.
three RD-curves, one for each channel) and 10 RD-points for MS-SSIM
(i.e. one RD-curve, for luma channel only) should be calculated in
the case of YCbCr. If content is encoded as RGB, 60 RD-points (30
for PSNR and 30 for MS-SSIM) should be calculated, i.e. three RD-
curves (one for each channel) are computed for PSNR as well as three
RD-curves (one for each channel) for MS-SSIM.
Finally, to obtain an integral estimation, BD-rate savings [13]
should be computed for each range and each quality index. In
addition, average values over all the 3 ranges should be provided
for both PSNR and MS-SSIM. A list of video sequences that should be
used for testing as well as the 10 QP values for the reference codec
are defined in [14]. Testing processes should use the information on
the codec applications presented in this document. As the reference
for evaluation, state-of-the-art video codecs such as HEVC/H.265
[4,5] or VP9 must be used. The reference source code of the
HEVC/H.265 codec can be found at [6]. The HEVC/H.265 codec must be
configured according to [16] and Table 11.
+----------------------+-------------------------------------------+
| Intra-period, second | HEVC/H.265 encoding mode according to [16]|
+----------------------+-------------------------------------------+
| AI | Intra Main or Intra Main10 |
+----------------------+-------------------------------------------+
| RA | Random access Main or |
| | Random access Main10 |
+----------------------+-------------------------------------------+
| FIZD | Low delay Main or |
| | Low delay Main10 |
+----------------------+-------------------------------------------+
Table 11. Intra-periods for different HEVC/H.265 encoding modes
according to [16]
According to the coding efficiency requirement described in Section
3.1.1, BD-rate savings calculated for each color plane and averaged
for all the video sequences used to test the NETVC codec should be,
at least,
o 25% if calculated over the whole bitrate range;
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o 15% if calculated for each bitrate subrange (LBR, MBR, HBR).
Since values of the two objective metrics (PSNR and MS-SSIM) are
available for some color planes, each value should meet these coding
efficiency requirements, i.e. the final BD-rate saving denoted as S
is calculated for a given color plane as follows:
S = min { S_psnr, S_ms-ssim },
where S_psnr and S_ms-ssim are BD-rate savings calculated for the
given color plane using PSNR and MS-SSIM metrics, respectively.
In addition to the objective quality measures defined above,
subjective evaluation must also be performed for the final NETVC
codec adoption. For subjective tests, the MOS-based evaluation
procedure must be used as described in section 2.1 of [3]. For
perception-oriented tools that primarily impact subjective quality,
additional tests may also be individually assigned even for
intermediate evaluation, subject to a decision of the NETVC WG.
6. Security Considerations
This document itself does not address any security considerations.
However, it is worth noting that a codec implementation (for both an
encoder and a decoder) should take into consideration the worst-case
computational complexity, memory bandwidth, and physical memory size
needed to processes the potentially untrusted input (e.g., the
decoded pictures used as references).
7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[1] Recommendation ITU-R BT.2020-2: Parameter values for ultra-
high definition television systems for production and
international programme exchange, 2015.
[2] Recommendation ITU-T G.1091: Quality of Experience
requirements for telepresence services, 2014.
[3] ISO/IEC PDTR 29170-1: Information technology -- Advanced image
coding and evaluation methodologies -- Part 1: Guidelines for
codec evaluation.
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[4] ISO/IEC 23008-2:2015. Information technology -- High
efficiency coding and media delivery in heterogeneous
environments -- Part 2: High efficiency video coding
[5] Recommendation ITU-T H.265: High efficiency video coding,
2013.
[6] High Efficiency Video Coding (HEVC) reference software (HEVC
Test Model also known as HM) at the web-site of Fraunhofer
Institute for Telecommunications, Heinrich Hertz Institute
(HHI): https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/
8.2. Informative References
[7] Definition of the term "high dynamic range imaging" at the
web-site of Federal Agencies Digital Guidelines Initiative:
http://www.digitizationguidelines.gov/term.php?term=highdynami
crangeimaging
[8] Definition of the term "compression, visually lossless" at the
web-site of Federal Agencies Digital Guidelines Initiative:
http://www.digitizationguidelines.gov/term.php?term=compressio
nvisuallylossless
[9] S. Wenger, "The case for scalability support in version 1 of
Future Video Coding," Document COM 16-C 988 R1-E of ITU-T
Video Coding Experts Group (ITU-T Q.6/SG 16), Geneva,
Switzerland, September 2015.
[10] "Recommended upload encoding settings (Advanced)" for the
YouTube video-sharing service:
https://support.google.com/youtube/answer/1722171?hl=en
[11] H. Yu, K. McCann, R. Cohen, and P. Amon, "Requirements for
future extensions of HEVC in coding screen content", Document
N14174 of Moving Picture Experts Group (ISO/IEC JTC 1/SC 29/
WG 11), San Jose, USA, January 2014.
[12] Manindra Parhy, "Game streaming requirement for Future Video
Coding," Document N36771 of ISO/IEC Moving Picture Experts
Group (ISO/IEC JTC 1/SC 29/WG 11), Warsaw, Poland, June 2015.
[13] G. Bjontegaard, "Calculation of average PSNR differences
between RD-curves," Document VCEG-M33 of ITU-T Video Coding
Experts Group (ITU-T Q.6/SG 16), Austin, Texas, USA, April
2001.
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[14] T. Daede, A. Norkin, and I. Brailovskiy, "Video Codec Testing
and Quality Measurement", draft-ietf-netvc-testing-08(work in
progress), January 2019, p.23.
[15] Z. Wang, E. P. Simoncelli, and A. C. Bovik, "Multi-scale
structural similarity for image quality assessment," Invited
Paper, IEEE Asilomar Conference on Signals, Systems and
Computers, Nov. 2003, Vol. 2, pp. 1398-1402.
[16] F. Bossen, "Common test conditions and software reference
configurations," Document JCTVC-L1100 of Joint Collaborative
Team on Video Coding (JCT-VC) of the ITU-T Video Coding
Experts Group (ITU-T Q.6/SG 16) and ISO/IEC Moving Picture
Experts Group (ISO/IEC JTC 1/SC 29/WG 11), Geneva,
Switzerland, January 2013.
9. Acknowledgments
The authors would like to thank Mr. Paul Coverdale, Mr. Vasily
Rufitskiy, and Dr. Jianle Chen for many useful discussions on this
document and their help while preparing it as well as Mr. Mo Zanaty,
Dr. Minhua Zhou, Dr. Ali Begen, Mr. Thomas Daede, Mr. Adam Roach,
Dr. Thomas Davies, Mr. Jonathan Lennox, Dr. Timothy Terriberry,
Mr. Peter Thatcher, Dr. Jean-Marc Valin, Mr. Roman Danyliw, Mr. Jack
Moffitt, Mr. Greg Coppa, and Mr. Andrew Krupiczka for their valuable
comments on different revisions of this document.
This document was prepared using 2-Word-v2.0.template.dot.
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Authors' Addresses
Alexey Filippov
Huawei Technologies
Email: alexey.filippov@huawei.com
Andrey Norkin
Netflix
Email: anorkin@netflix.com
Jose Roberto Alvarez
Huawei Technologies
Email: j.alvarez@ieee.org
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