Estimating time offset between two audio signals.

robert bristow-johnson <rbj@audioimagination.com> wrote in
news:a5e2fb34-f356-46cb-835c-a6703bfe61f5@a14g2000vbm.googlegr
oups.com: 

> On Apr 19, 6:12&#4294967295;pm, "dszabo" <62466@dsprelated> wrote:
>> >On 4/19/2013 3:32 PM, dszabo wrote:
>> >> I should probably point out that your capacity to
>> >> calculate a delay is dependent on the presence of
>>
>> >Q: Why it is impossible to have sex in Red Square in
>> >Moscow ? A: Because every bystander idiot would be trying
>> >to give his invaluable advice.
>>
>> >Vladimir Vassilevsky
>> >DSP and Mixed Signal Designs
>> >www.abvolt.com
>>
>> I love this guy! &#4294967295;Can we hang out some time? &#4294967295;Grab a drink
>> and talk a 
> bout
>> the finer points of Kalman filters?
> 
> might have to wait until the next comp.dsp conference.  i
> missed the first two, but will endevour to make it to the
> next one, whenever it is.
> 
> r b-j

Vlad hosted one and I hosted the other, I guess you're up 
Robert, Have you set a date?

Al

On 4/22/2013 8:24 AM, Mauritz Jameson wrote:
> Vlad,
>
> You wrote:
>
> "Estimate the rate of upcomming/outgoing data. Resample the data so
> everything would work as if it is on the same sample clock."
>
> I think that's something you would do if you have sample rate drift?
> Meaning: You get more or less far-end data per second than near-end
> data, right? This is not the problem in this case. The problem is the
> audio subsystem. The delay on the transmission path between the
> digital speaker buffer (which stores incoming audio from RTP) and the
> digital microphone buffer (which stores audio delivered to the
> application by the audio driver) varies too much (sudden jumps by
> more than 30ms). By transmission path I mean:
>
> digital spk buffer -> audio driver (spk)  -> acoustic path -> audio
> driver (mic) -> digital mic buffer
>
> The delay on the acoustic path is naturally constant.
>

If there is no sample clock slip, then the issue could be fixed by 
sufficient buffering. Why is the problem?

VLV

Vlad,

The problem is the audio driver. It doesn't always accept speaker data. So if I have speaker data that I want to send to the audio driver I can either wait until the audio driver accepts the data or throw it away. On top of that, the audio driver doesn't always return mic data. So what do I do then? Wait until it becomes available or substitute the missing data with silence packets?