- From: Bernard Aboba via GitHub <sysbot+gh@w3.org>
- Date: Thu, 04 Oct 2018 05:43:39 +0000
- To: public-webrtc-logs@w3.org
@Orphis `setCodecPreferences` affects which codecs are included in `createOffer` or `createAnswer`. For this purpose, either `RTCRtpSender.getCapabilities(kind)` or `RTCRtpReceiver.getCapabilities(kind)` may be relevant, depending on the direction indicated (`sendrecv`, etc.). With respect to the Offered codecs, RFC 3264 Section 5.1 says: The list of media formats for each media stream conveys two pieces of information, namely the set of formats (codecs and any parameters associated with the codec, in the case of RTP) that the offerer is capable of sending and/or receiving (depending on the direction attributes), and, in the case of RTP, the RTP payload type numbers used to identify those formats. If multiple formats are listed, it means that the offerer is capable of making use of any of those formats during the session. In other words, the answerer MAY change formats in the middle of the session, making use of any of the formats listed, without sending a new offer. For a sendonly stream, the offer SHOULD indicate those formats the offerer is willing to send for this stream. For a recvonly stream, the offer SHOULD indicate those formats the offerer is willing to receive for this stream. For a sendrecv stream, the offer SHOULD indicate those codecs that the offerer is willing to send and receive with. For the codecs in the Answer, RFC 3264 Section 6.1 says: For streams marked as recvonly in the answer, the "m=" line MUST contain at least one media format the answerer is willing to receive with from amongst those listed in the offer. The stream MAY indicate additional media formats, not listed in the corresponding stream in the offer, that the answerer is willing to receive. For streams marked as sendonly in the answer, the "m=" line MUST contain at least one media format the answerer is willing to send from amongst those listed in the offer. For streams marked as sendrecv in the answer, the "m=" line MUST contain at least one codec the answerer is willing to both send and receive, from amongst those listed in the offer. The stream MAY indicate additional media formats, not listed in the corresponding stream in the offer, that the answerer is willing to send or receive (of course, it will not be able to send them at this time, since it was not listed in the offer). For streams marked as inactive in the answer, the list of media formats is constructed based on the offer. If the offer was sendonly, the list is constructed as if the answer were recvonly. Similarly, if the offer was recvonly, the list is constructed as if the answer were sendonly, and if the offer was sendrecv, the list is constructed as if the answer were sendrecv. If the offer was inactive, the list is constructed as if the offer were actually sendrecv and the answer were sendrecv. -- GitHub Notification of comment by aboba Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1998#issuecomment-426892214 using your GitHub account
Received on Thursday, 4 October 2018 05:43:41 UTC