[ntp:questions] Accuracy of audio tones via VOIP

Rob nomail at example.com
Tue Jul 9 19:46:35 UTC 2013

Robert Scott <no-one at notreal.invalid> wrote:
> 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?

Would you be setting your clock to the hour pips as heard on the internet
stream of a radio station?

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