[ntp:questions] Accuracy of audio tones via VOIP

Robert Scott no-one at notreal.invalid
Tue Jul 9 19:25:34 UTC 2013

On Tue, 09 Jul 2013 18:59:05 +0100, David Woolley
<david at ex.djwhome.demon.invalid> wrote:

>On 09/07/13 15:35, Robert Scott wrote:
>> as much as the local quartz oscillator frequencies?  Does anyone have
>> any insight on how Skype and other VOIP systems manage record/playback
>> rate synchronization?
>The workings of Skype are a trade secret.  Other ones will have a jitter 
>buffer, and will typically dump or repeat frames if that gets too full 
>or risks underflowing.  RTP allows the source to mark good places to do 

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?

More information about the questions mailing list