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

[Christian Affolter]

On 31.01.2018 21:22, Thomas Brand wrote:
> On Wed, January 31, 2018 15:55, Christian Affolter wrote:
>> On 31.01.2018 15:20, Kjetil Matheussen wrote:
>>> Maybe jack will work if you give it the same parameters that arecord
>>> uses. I.e. compare the content of
>>>  /proc/asound/card0/pcm0p/sub0/hw_params (or a similarly
>>> named file) when running arecord and when running jack.
>>>
>>> Also, maybe it works to record in jack if you change audio from
>>> "duplex"
>>> to "capture only".
>>
>> BINGO and thank you so much for this pointer!
> 
>>
>>
>> # hw_params during jackd -d alsa -d hw:0
>> # jackd -d alsa
>> cat /proc/asound/card0/pcm0c/sub0/hw_params
>>
>> access: MMAP_INTERLEAVED
>> format: S32_LE
>> subformat: STD
>> channels: 8
>> rate: 48000 (48000/1)
>> period_size: 1024
>> buffer_size: 2048
>>
> 
> What i wonder is did you see 8 JACK system:capture ports with the above
> configuration? 

yes, there are 8 ports available:

jack_lsp -c -t

system:capture_1
	32 bit float mono audio
[...]
system:capture_8
	32 bit float mono audio
system:playback_1
	32 bit float mono audio
[...]
system:playback_8
	32 bit float mono audio



> It's still confusing that JACK would attach the device
> differently. The factor 4 can probably be explained by 8 / 2 channels (?)
> or has it do with duplex?.
> It could be that the record just took every 4th sample. But why?

I guess it has something to do with the fact, that I only have the first
Livewire+ Destination on the Axia-ALSA driver configured (which equals
to the first two system capture ports in jackd) to actually receive RTP
streams from the Livewire+ network. The other 3 stereo Livewire
Destinations (6 system capture channels) are not configured. However,
this is just a speculation and I would have to verify that, by
configuring more than one Livewire destinations.

But anyway, it's a pretty unexpected recording behaviour. Either the
driver shouldn't block (or whatever it's doing) or jackd would need a
way to detect that only two of the ports are actually working, which is
most likely outside of jackd's responsibility.


> For future reference, this could be issued on github with these detailed
> debug informations. It's possible that JACK can't do anything about it if
> it's driver related. So.. up to you.

I can do this, if anyone thinks that this issue might be of any help
and/or someone is willing to spend more time to actually debug this
within the jackd source code. On the other hand, it's kind of documented
on the mailing list archive by now for others to find.


>> # hw_params during jackd -d alsa -d hw:0 -C -i 2
>> cat /proc/asound/card0/pcm0c/sub0/hw_params
>>
>> access: MMAP_INTERLEAVED
>> format: S32_LE
>> subformat: STD
>> channels: 2
>> rate: 48000 (48000/1)
>> period_size: 1024
>> buffer_size: 2048

Thanks again for your help
Chris