[Jack-Devel] Capture problems with jack2 on Axia-Alsa device

[Thomas Brand]

On Tue, January 30, 2018 19:46, Christian Affolter wrote:
> Hi Thomas,
>
>
> On 30.01.2018 18:15, Christian Affolter wrote:
>
>> On 30.01.2018 16:23, Christian Affolter wrote:
>>
>>>> the alsa device could be the issue. you could try to start a dummy
>>>> jack and add the alsa device with alsa_in to see if it makes a
>>>> difference.
>
> This seems to work, the audio gets captured (and can be played)
> correctly. Here is what I did:
>
> # Start jackd with the dummy backend
> jackd -d dummy
>
> # Add the alsa device via alsa_in
> alsa_in -d hw:0 -c 2
>
>
> # Capture via jack_capture
> jack_capture -b 32 -c 2 -d 10 -fn /tmp/test-jack_capture.wav \ -p
> alsa_in:capture_1 -p alsa_in:capture_2
>
>
> # Capture via jackrec
> jackrec -f /tmp/test-jackrec.wav -d 10 -b 32 alsa_in:capture_1
> alsa_in:capture_2
>
>
>
> What I also observed is the fact, that capturing 10 seconds
> (jack_capture -d 10 ...) directly from the "-d alsa" jackd takes around
> 40 seconds (real 0m40.457s) vs. 10 seconds (as one would expect) with
> the "-d dummy" jackd (real 0m10.339s)
>
> So I guess we're one step closer.
>
>

now that's an interesting find .. in theory it should not make a
difference if jack uses alsa backend or if you attach via alsa_in but
obviously it *does* make a difference.

40 seconds is the length when played at 12k.
4 x 8 bit also fit into 32 bit. something is fishy.

>
> Thanks a lot for your help
> Chris
>
>