Re: [codec] I-D Action: draft-ietf-codec-oggopus-11.txt

"Timothy B. Terriberry" <tterribe@xiph.org> Tue, 02 February 2016 23:40 UTC

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Subject: Re: [codec] I-D Action: draft-ietf-codec-oggopus-11.txt
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>      It is possible to run an Opus decoder at other sampling rates, but
> a sampling rate of 48 kHz is sufficient to capture the full audio
> bandwidth of any Opus packet.  Therefore, the value in the granule
> position field always counts samples assuming a 48 kHz decoding rate
> ...

I think this loses the important property that the other sample rates 
evenly divide 48 kHz. That property implies that a 48 kHz rate is 
sufficient to capture sample-accurate timing information without having 
to introduce specific rules around propagation of rounding errors, etc., 
regardless of the sample rate used at either endpoint. That is why we 
chose 48 kHz instead of say, 40 kHz (which would also have been 
sufficient to capture the full audio bandwidth, but would have made 
sample-accurate operations quite cumbersome).

Would you be satisfied with saying, "It is possible to run the decoder 
in the Opus reference implementation at other sampling rates..." instead?