Payload Type

[aboba]

From Iñaki Baz Castillo [[email protected]]:

When I create a RTCRtpSender instance and add a track and
then get the RTCRtpCapabilities.codecs, would them indicate the
sending RTP payload? or the payload to expect in the incoming RTP
packets in the same transport?

IMHO it makes lot of sense that those payload values are the sending
ones (given that this is not SDP O/A party and thus there is no need
to negotiate incoming RTP when we send), but in the case of "SDP O/A
emulation", does it mean that I should "manually" override those
"payload" values with the remote info once I've initiated my
RTCRtpSender and received the remote "description"?

[aboba]

This does not appear to be an API issue, as noted by Robin:
http://lists.w3.org/Archives/Public/public-ortc/2014Sep/0002.html

However, it might be worth clarifying getCapabilities() behavior as noted here:
http://lists.w3.org/Archives/Public/public-ortc/2014Sep/0001.html

[aboba]

Potential clarification to Section 9.4.1 is to add the following text to the definition of preferredPayloadType:

preferredPayloadType of type payloadtype
The preferred RTP payload type for the codec denoted by RTCRtpCodecCapability.name. Where RTCRtpCapabilities.codecs.preferredPayloadtype is provided via calling RTCRtpSender.getCapabilities() it represents the preferred RTP payload type for sending; where it is returned via calling RTCRtpReceiver.getCapabilities() it represents the preferred RTP payload type for receiving. Overall, this attribute was added to make it possible for the sender and receiver to pick a matching payload type when creating sender and receiver parameters. To avoid potential payload type conflicts, the value of RTCRtpCodecCapability.preferredPayloadtype should be different for each value of RTCRtpCodecCapability.name.

[aboba]

Proposed revision for clarity:

"The preferred RTP payload type for the codec denoted by RTCRtpCodecCapability.name. This attribute was added to make it possible for the sender and receiver to pick a matching payload type when creating sender and receiver parameters. When returned by RTCRtpSender.getCapabilities(), RTCRtpCapabilities.codecs.preferredPayloadtype represents the preferred RTP payload type for sending. When returned by RTCRtpReceiver.getCapabilities(), RTCRtpCapabilities.codecs.preferredPayloadtype represents the preferred RTP payload type for receiving. To avoid payload type conflicts, each value of RTCRtpCodecCapability.name should have a unique value of RTCRtpCodecCapability.preferredPayloadtype."

[ibc]

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