Re: [MMUSIC] IETF#89: BUNDLE: Q9: What are the criteria for allowing usage of the same PT value within multiple m- lines?

[Christer Holmberg <[e-mail]>]

Hi,
Assume you have two video m- lines.
On both m- lines, you indicate that you can receive a codec using PT value Y.
Then, you receive a video media packet, with PT value Y, and SSRC value 1234567. How do you know which of the two m- lines this media packet is associated with?
We've discussed this multiple times before. If payload types numbers are unique across m= lines, then obviously you can use them to identify the m= line. If you reuse payload type values across m= lines, then you need some other way of identifying m= lines, if you care about doing so. Signalled SSRC values are one approach, something like AppID might be another.

...which takes us back to what I said in the beginning: when you send your initial offer, and assign the PT values you want to receive, you don't know whether the remote peer supports AppID, or whatever other mechanism that could be used.

Regards,

Christer