Hello, Magnus,
Magnus Westerlund wrote:
Hi Sassan,
Based on what you write in the previous mail. It seems that the only
reason for using different RTP timestamp rate between 8000 and 16000
Hz is to indicate the sampling rate of the source material. If the
codec does not need any indication at all if the source material is
8k or 16k then, I think the usage of different RTP timestamp rates is
creating unnecessary interoperability barriers. The barrier is that
one actually needs to indicate the rate of the source material, and
cope with RTP timestamp switching.
Right on! You nailed the issue perfectly.
To avoid the unnecessary function I would propose that VMR-WB only
defines 16kHz as RTP timestamp rate.
Agreed. This would effectively remove the interoperability barrier you
pointed out above.
My only concern is that this may create some interesting situations.
Let's consider an example - original speech of 8k rate is passed to
vmr-wb encoder and the decoder is set to output speech at 8k rate.
Here, we would then have:
- source sampling rate = 8k
- actually sampling rate of the bit stream sent over RTP = 12.8k
- sampling rate output from vmr-wb = 8k
- RTP header timestamp rate = 16k!!!
I am not sure this will cause any problem, but it seems strange.