Re: [MMUSIC] Offer/Answer PT Questions

[Christer Holmberg <[e-mail]>]

Hi,

>> 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.

The current rule may be easy to understand, but it's difficult to understand - and that's what triggered this discussion :)

So, while we can discuss possible rules/guidelines on when a PT value can be used, I still think we need to answer the first question:

- If Alice allocates PT=X for codec 1, is Bob allowed to allocate PT=X for codec 2 within the same session? The current text is unclear on that, and I think that is the first question we need to sort out.

After that, we can discuss whether e.g. Alice at some point can allocate PT=X for codec 3, and what the criteria for that is.

Regards,

Christer