Re: [MMUSIC] Offer/Answer PT Questions

[Paul Kyzivat <[e-mail]>]

On 2/23/16 5:29 AM, Colin Perkins wrote:

> No objection in principle, but it’s not as simple as “a few network RTTs”:
>
> No ambiguity in decoding means that the packets need to have been played
> out, so the codec state for that PT can be discarded. Some systems can
> have large (multi-second) playout buffers.
>
> Any packets referring to the old PT also need to be gone. Formats
> like RFC 6354 allow large offsets between streams, referenced by PT (the
> example in Section 5 has a 5.1 second offset).

Thanks for the insight. It helps to ground the discussion.

I'm also interested in hearing if there might be *other* reasons behind 
the rules as they are written.

The advantage of the current rule is that it is easy to explain, and is 
sufficient to deal with the problem you describe above. Unfortunately it 
is also difficult/impossible to comply with in some cases. If we are to 
replace it, we need to find something else to replace it with.

Would it be possible to instead make a rule that a PT can't be reused 
until there are no active streams using it? (That any that were 
initiated have been terminated.) Note: I don't know RTP well enough to 
be confident that this even makes sense.

	Thanks,
	Paul