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

[Colin Perkins <[e-mail]>]

On 3 Mar 2014, at 11:05, Christer Holmberg <[e-mail]> wrote:
> Hi,
> >The same way you separate every other stream: SSRC to identify the media source, then direct to >the right decoder path based on the PT mapping table. 
>  
> Yes, but then you need to know which SSRC(s) are going to be used for each media stream.
>  
> Huh? You may have to explain, because I don’t see that.
>  
> 
> 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.  


-- 
Colin Perkins
http://csperkins.org/