Re: [codec] #8: Sample rates? 44.1kHz?

-Support of 48 kHz in sound cards, etc. is quite widespread, so personally I
see no requirement for 44.1 kHz (or 22.05, 11.025).

-RTP timestamp granularity of 96 kHz would be pretty hard to get through,
unless we actually have a 96 kHz mode of operation.  I don't see any
requirement for such a mode (though CELT happens to do it)

Might be worth summarizing where we are at this point:

-There appears to be a consensus that the RTP time base needs to remain
constant despite any changes to acoustic bandwidth. (due to network
adaptation)

- There is a consensus that frequent changes to acoustic bandwidth results
in a disturbing / unpleasant listening experience.

- There is consensus that it is ok to reduce the acoustic bandwidths at
lower bitrates,

- There is no consensus (as of yet) as to how many or which sampling rates
we need for the "internal codec", including no consensus that we need more
than one.  It is important to note that no one has *objected* to multiple
sample rates either. Though it has been observed that multiple sample rates
makes compressed domain mixing problematic.

Stephen Botzko

On Fri, Apr 16, 2010 at 12:44 AM, Christian Hoene <hoene@uni-tuebingen.de>wrote:

> Hi all,
>
> >It might be useful to state that it is not recommended to use 44100 Hz,
> because the conversion to
> >16kHz and 32kHz is computational more demanding than 48kHz and requires
> more power/time.
>
> Currently, proposed codec run at sampling rates of
>
> BroadVoice: 8, 16 kHz
> SILK: 8, 12, 16, 24 kHz
> CELT: 32 kHz to 96 kHz.
>
> I do have a question. In order to make the RTP handling and the resampling
> simpler, it might be useful to skip the 44.1kHz compression mode. If only 8,
> 12, 16, 24, 32, and 48 kHz sampling rates are used, then the RTP timestamp
> can be easily counted in 96 kHz units. Supporting 44.1 kHz would require
> fractions of time stamp units that are difficult to handle with. Also, the
> resampling take more computational resource if it has to be done at high
> quality.
>
> Thus, my question: Is 44.1 kHz really much-needed or can we use 32 or 48
> kHz instead?
>
> Christian
>
>
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