Re: [AVT] The RTP payload format for multichannel codecs's signalling problem

[Magnus Westerlund <magnus.westerlund at ericsson.com>]

Hi Ross,

I don't think that is a good solution due to that if one is only capable 
of handling mono playback, then one might refuse to use this 
functionality, although one would in fact be able to support it. 
Therefore it seems rather important to be able to downgrade a channel 
setup from maximum to a small set. For a more critical example one might 
not support 6+1 channel, however one is interested of using 2 channels.

Secondly, I don't know if the set of possible channels is obvious what 
requires less capability between all possible configuration. Is a 
quadraphonic setup less or more than a L+R, Center and Surround setup? 
Having explicit declaration of all used channel modes avoid these problems.

Cheers

Magnus

Ross Finlayson wrote:

> It seems to me that for any codec that carries channel etc. parameters 
> inband - and allows these parameters to change 'on the fly' - there is
> an 
> implicit assumption that each receiver should be able to handle all 
> possible settings of these inband parameters.  So, given this, your
> first 
> proposed solution seems to make the most sense: Declare the AMR-WB+ RTP 
> payload type to be for stereo, even though all frames within such a
> stream 
> might actually turn out to be mono.
>
> 	Ross.
>
>
> _______________________________________________
> Audio/Video Transport Working Group
> avt@ietf.org
> https://www1.ietf.org/mailman/listinfo/avt
>
>  
--

Magnus Westerlund 
Multimedia Technologies, Ericsson Research EAB/TVA/A
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