Re: [Discuss-gnuradio] Correct multiple audio cards clock differences

[Murray Thomson]

Thanks Marcus,

It sounds like a good idea but I think I haven't explained my flow graph well enough. This a simplification of what I've got.

I've taken away one of the cards, filters and others. Can I still use your approach using "streams to vector" -> "vector to streams" in this situation?

Thanks,

Murray

On 13 January 2016 at 10:10, Marcus Müller <address@hidden> wrote:

Well, that could well be; at 96kHz, 1s after a day is a drift of

which would be a relatively good value for soundcard oscillators.

For drifts that small, you probably won't be able to correct this from signal.

I'd say, since you can live with dropping samples, do the following:

source 1   ->                                       ->
...        ->streams to vector -> vector to streams ->
source N   ->                                       ->

that enforces sample-synchronity. You then set a maximum size for the output buffers of the source blocks, if you'd rather lose few samples then seeing a growing delay and then lose a bigger bunch of samples.

Best regards,
Marcus

On 01/13/2016 08:30 AM, Murray Thomson wrote:

Hi,

I'm using three audio cards in my flow graph. The internal and a USB audio cards run at 96 kHz and I use a virtual audio card with 5 subdevices loading the snd_aloop kernel module that runs at 48 kHz.

I've noticed that after some days of running there seems to be a delay (around 1 second) processing the signal.

I was wondering if this could be due to the differences in the clocks of the audio cards. Is there a way to correct these differences? I can afford losing data every now and again, but an increasing delay it's a problem for me.

Thanks,

Murray

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