RE: [AVT] retransmission payload format

[David.Leon@nokia.com]

Hi,

> >>>It also becomes difficult to use header compression, if 
> the retransmitted
> >>>packets are sent as a separate stream.
> >>>
> >>I would not say it becomes difficult to use header compression. The 
> >>efficiency will simple be less as the RTP TS must be sent 
> using more 
> >>bits or uncompressed. But as the retransmitted stream uses 
> much less 
> >>bandwidth than the original stream I would think it is a 
> minor problem.
> >>
> >
> >This was what I meant: the compression is likely to be 
> seriously impacted.
> >We may not care, since retransmission packets will hopefully be rare.
> >
> I guess this depends on the compression type. In the case of the ROHC 
> RTP profile it will only mean that each packets header 
> becomes up to 2 
> bytes bigger compared to a optimal performance. But maybe some of the 
> other standards has worse performance.

As mentioned by Magnus, the worst thing that can happen (at least with ROHC) is that you need more bits to send the compressed TS. Efficiency-wise, it is nevertheless better than using the sending time TS as in the latter case you have to send the compressed TS plus the full original media TS in the RTP payload.

David.  
 
_______________________________________________
Audio/Video Transport Working Group
avt@ietf.org
https://www1.ietf.org/mailman/listinfo/avt