measuring audio latency?

[Avery Pennarun]

On Tue, Mar 9, 2010 at 9:15 AM, Dan Kegel <dank at kegel.com> wrote:
> On Tue, Mar 9, 2010 at 2:58 AM, Roderick Colenbrander
> <thunderbird2k at gmail.com> wrote:
>> I might be able to measure it using my oscilloscope. Somehow I would
>> need to play lets say the left channel 'without' latency and the other
>> channel with and compare the two signals.
>
> Yes, absolutely, but it'd be good to make this measurement easy
> to repeat by anybody interested.  To do that, let's just loop the
> audio output back into the audio input.  The user will have to
> provide a loopback cable (or, worst case, put his mike right up
> to the speaker, and allow for a tiny bit of extra latency
> from that).

If sound travels at 340m/s, then a one-second sample is 340m long.  A
1ms delay would therefore be 340mm, or 34 cm.  Your mic would have to
be *quite* far away from the speakers to have a significant impact on
the delay, unless I'm missing something.

Which is good news, I guess, since it means tests are easier.  Hope it
goes well :)

Have fun,

Avery