MPEG-5 EVCコーデックメモ

# MPEG-5 EVC
https://mpeg.chiariglione.org/standards/mpeg-5/essential-video-coding
正式名称「MPEG-5 Part 1 Essential Video Coding」

- [ISO/IEC 23094-1 Essential video coding](https://www.iso.org/standard/57797.html)

[特許問題により普及しないH.265/HEVCコーデック][hevc-licensing]の代替を狙った、ライセンス・フレンドリ(licensing-friendly)な動画像コーデック。
[hevc-licensing]: https://qiita.com/yohhoy/items/c2579097a507b1fbdddb


## 目的
- ロイヤリティフリー(RF; Royalty-Free)な枯れた技術[^legacy-tech]のみを用いる Baseline Profile と、特許技術を用いてより高効率を目指す Main Profile という2オプションを提供する。
  - ロイヤリティフリー・コーデック運用ができるよう、任意の Main Profile 向け符号化ツールは選択的に無効化可能。
  - Baseline Profile準拠エンコーダ／デコーダを用いて、Baseline Profile準拠ビットストリームを配信・記録・再生する場合に限ってロイヤリティフリーとなる。
- H.265/HEVCコーデック相当の圧縮性能、リアルタイム処理可能な計算複雑性を目指す。
- 従来MPEG標準化プロセスよりもタイムリーなコーデック開発と市場投入を行う。

[^legacy-tech]: 特許権の存続期間が終了、つまり20年以上前に公知となった技術。


# 符号化スキーム
古典的MC+DCTハイブリッド方式
<img width="810" alt="Coding scheme" src="https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/6657/ffd43e36-255b-46b6-cec4-7a1c0128678c.png">

- 最大 8K/120fps までサポート
- Monochrome, YUV 4:2:0, (仕様上は4:2:2, 4:4:4サポート有)
- 8 bit/pixel, 10 bit/pixel (仕様上は8～16 bit/pixelサポート)


## Baseline Profile

- High-level syntax
  - Network Abstraction Layer (NAL) units w/ temporal ID
  - Sequence Parameter Set (SPS)
  - Picture Parameter Set (PPS)
  - Adaptation Parameter Set (APS)
- Entropy coding
  - JPEG Annex D arithmetic coding
  - run-level coefficient coding
- Coding structure
  - Quad-tree coding structure
  - up to 64x64 CTU 
- Intra prediction
  - Square-shaped prediction block
  - 5 mode (DC/V/H/2 diagonals)
- Inter predication
  - Uni-directional (P-frame)
  - Bi-directional (B-frame)
  - multiple reference pictures
  - 1/4-pel Motion Compensation w/ interpolation filter
  - 3 spatial neighbouring motion vector predicator
  - 1 temporal collocated motion vector predicator
  - Skip mode (no mvd, no residual)
- Inverse quantization and transform
  - integer Discrete Cosine Transform
  - scalar quantization w/ look-up table
- In-loop filtering
  - H.263 Annex J deblocking filter
- Decoded Picture Buffer
  - sequence level control


## Main Profile
- High-level syntax
  - Picture Order Count Signaling (POCS)
  - Reference Picture Lists (RPL)
- Entropy coding
  - Context Modeling and Initialization (CMI)
- Coding structure
  - rectangular TILES
  - Binary Ternary Tree (BTT)
  - Split Unit Coding Order (SUCO)
- Intra prediction
  - Enhanced Intra Prediction Directions (EIPD)
  - Intra Block Copy (IBC)
- Inter predication
  - Advanced Motion Interpolation and Signaling (AMIS)
  - Merge with Motion Vector Difference (MMVD)
  - Advanced Motion Vector Prediction (ADMVP)
  - Adaptive Motion Vector Resolution (AMVR)
  - AFFINE prediction mode
  - Decoder-side Motion Vector Refinement (DMVR)
- Inverse quantization and transform
  - Improved Quantization and Transform (IQT)
  - Adaptive Transform Selection (ATS)
  - Advanced Coefficient Coding (ADCC)
- In-loop filtering
  - Hadamard Transform Domain Filter (HTDF)
  - Advanced Deblocking Filter (ADDB)
  - Adaptive Loop Filter (ALF)
- Decoded Picture Buffer
  - flexible picture level control


# ライセンス
https://www.csimagazine.com/csi/MPEG-5-EVC-gets-final-approval.php
> According to MPEG, the EVC standard offers improved compression efficiency compared to existing video coding standards and is based on the statements of all contributors to the standard who **have committed to announce their license terms for the MPEG-5 EVC standard no later than two years after the FDIS publication date.**

ISO/IEC 23094-1:2020, Stage 50.00 FDIS registered (2020-05-18)


# 業界動向
2020/5/8, Qualcomm・Samsung・Huawei 3社連名にて "Welcome the Release of a New Video Coding Standard" を表明。3社計ではスマートフォン向けチップセット市場シェア 60% (2019年)[^share2019]を占める。

- [Qualcomm](https://www.qualcomm.com/media/documents/files/mpeg-5-evc-joint-statement.pdf)
- [Samsung Electronics](https://research.samsung.com/news/Samsung-Electronics-Huawei-and-Qualcomm-Welcome-the-Release-of-a-New-Video-Coding-Standard)
- [Huawei (HiSilicon)](https://www.huawei.com/en/news/2020/5/Qualcomm-and-Samsung-Electronics)

[^share2019]: https://www.counterpointresearch.com/samsung-became-third-largest-smartphone-application-processor-vendor-globally-2019/


# 参考情報
- [MPEG-5 Essential Video Coding (EVC)](https://www.itu.int/en/ITU-T/Workshops-and-Seminars/20191008/Documents/Ken_McCann_Presentation.pdf), Ken McCann(Chairman of MPEG Ad hoc Group on EVC)
- [The emerging MPEG-5 EVC standard - Applications, technology and results](https://www.ibc.org/publish/the-emerging-mpeg-5-evc-standard-applications-technology-and-results/5061.article)
- [What is Essential Video Coding (EVC) MPEG-5 Part-1?](https://ottverse.com/guide-to-essential-video-coding-evc-mpeg5-part1/), 2021/2
- [次世代映像符号化方式EVCとVVCの性能比較調査](https://www.soumu.go.jp/main_content/000739576.pdf), 2021/3
- [Open-Source Project for MPEG-5 EVC (Essential Video Coding)](https://research.samsung.com/news/Open-Source-Project-for-MPEG-5-EVC-Essential-Video-Coding), 2021/7
- [Testing EVC, VVC, and LCEVC: How Do the Latest MPEG Codecs Stack Up?](https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=150729), 2021/12