- From: Harald Alvestrand via GitHub <sysbot+gh@w3.org>
- Date: Thu, 21 Nov 2019 07:43:19 +0000
- To: public-webrtc-logs@w3.org
Furthermore .... as I understand codec definitions in SDP, payload types can never *change*.
PTs defined in an offer define a set of codecs (A, B, C).
PTs in an answer (example: B, C, D) mean:
- I'm not willing to receive A
- I'm willing to receive B, perhaps with a more restricted profile (down-negotiating), and may choose to send it according to the profile you originally sent me
- I'm willing to receive C (same as above)
- I'm willing to receive D, but I'm not going to send it, since you haven't said you can receive it
D may be a superset of A's profile ("I want to negotiate up"), or completely unrelated.
So the set of codec descriptions can expand, and some of the descriptions can be rendered unusable ("I am not willing to receive") - but they cannot be redefined, and they cannot be reused.
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Received on Thursday, 21 November 2019 07:43:21 UTC