6.1 and WebRTC codecs for web pages
The evaluation of 6.1 in an accessibility audit for the WAD is quite difficult without any technical information coming from the technical provider (e.g. black box evaluation). As the WebRTC standard is now mentioned in 6.2.3 (v4.1.1a), would it be possible to mention in 6.1 which WebRTC audio codecs are compliant with the requirements of 6.1?
Examples of compliant codecs, according to our analysis:
- Opus Wideband (WB)
- Opus Super Wideband (SWB)
- Opus Fullband (FB)
- G.722
- iSAC
Examples of non-compliant codecs, according to our analysis:
- Opus Narrowband (NB)
- Opus Mediumband (MB)
- G.711 PCM
- iLBC
Only Opus and G.711 PCM are required in all implementations of the WebRTC standard, according to RFC 7874.
The selection of an audio codec is done for every WebRTC audio connection and is based on a negociation between the client and the server. This negociation can be fine-tuned on the client-side to avoid some codecs.
Proposal: Include examples of WebRTC audio codecs which comply with 6.1: Opus Wideband, Opus Super Wideband, Opus Fullband, G.722, iSAC, and mention that G.711 PCM, which is an audio codec required for all WebRTC implementations, is not compliant with 6.1.