4 # Video coding in WebRTC
6 ## Introduction to layered video coding
8 [Video coding][video-coding-wiki] is the process of encoding a stream of
12 ### Block-based hybrid video coding  argument
14 All video codecs in WebRTC are based on the block-based hybrid video coding
19 [transform][transform-coding-wiki] and [quantization][quantization-wiki] of the
21 transform coefficients, is losslessly [entropy coded][entropy-coding-wiki] along
39 ### Single-layer coding  argument
45 using "single-layer coding", where each delta frame only depends on the frame
48 ### Scalable video coding  argument
53 [scalable video coding][svc-wiki] can be used. The idea is to introduce
76 prediction generally offers superior coding efficiency compared with simulcast.
78 simulcast generally provides better coding efficiency for the upper spatial
86 Given the general introduction to video coding above, we now describe some
87 specifics of the [`modules/video_coding`][modules-video-coding] folder in WebRTC.
89 ### Built-in software codecs in [`modules/video_coding/codecs`][modules-video-coding-codecs]
92 implementations for different video coding standards:
103 ### Video codec test framework in [`modules/video_coding/codecs/test`][modules-video-coding-codecs-…
108 ### SVC helper classes in [`modules/video_coding/svc`][modules-video-coding-svc]
117 ### Utility classes in [`modules/video_coding/utility`][modules-video-coding-utility]
127 ### General helper classes in [`modules/video_coding`][modules-video-coding]
134 ### Receiver buffer classes in [`modules/video_coding`][modules-video-coding]
140 [video-coding-wiki]: https://en.wikipedia.org/wiki/Video_coding_format
142 [transform-coding-wiki]: https://en.wikipedia.org/wiki/Transform_coding
158 [entropy-coding-wiki]: https://en.wikipedia.org/wiki/Entropy_encoding
159 [modules-video-coding]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc…
160 [modules-video-coding-codecs]: https://source.chromium.org/chromium/chromium/src/+/main:third_party…
161 [modules-video-coding-codecs-test]: https://source.chromium.org/chromium/chromium/src/+/main:third_…
162 [modules-video-coding-svc]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/we…
163 [modules-video-coding-utility]: https://source.chromium.org/chromium/chromium/src/+/main:third_part…