[ntp:questions] Accuracy of audio tones via VOIP

David Woolley david at ex.djwhome.demon.invalid
Tue Jul 9 23:08:05 UTC 2013

On 09/07/13 20:25, Robert Scott wrote:

> That does not sound too encouraging for the pitch accuracy of tones
> transmitted over Skype.  Of course you would never notice it in normal
> speech, which is, I guess, all that Skype is targetting.  But for
> calibrating to the standard frequency tones from NIST (500 Hz and 600
> Hz), it probably is not trustworthy, right?

You are assuming that it uses a codec providing a 3.1kHz audio, rather 
than a speech, bearer service.  That is very unlikely.  I think you will 
find that pure tones are completely mutilated, particularly with respect 
to phase, in Skype, because it will actually use a vocoder based codec.

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