[LAD] JACK and ALSA elucidations

[Gianfranco Ceccolini]

Hi Guys

sorry for the delay. carnival time here in Brasil...

Jeremy: I’m using the BB Audio Cape, v1. I’ll take a look at the audio driver, but from our tests the BBB cpu won’t do the job.  We’re heading to the Cubie’s A20 cpu.

Paul. I’m really sorry for my lack of comprehension, but I still don’t get it.  Is there a relation between the ALSA period with JACK’s period?

Kind regards

Gianfranco
The MOD Team



Em 28/02/2014, à(s) 17:01, Jeremy Jongepier <jeremy at autostatic.com> escreveu:

> On 02/28/2014 06:57 PM, Gianfranco Ceccolini wrote:
>> When starting it on the Beaglebone Black I get:
>> 
>> 
>> /usr/bin/jackd --realtime -P80 -dalsa -r48000 -p128 -n2 -Xraw
>> 
>> 
>> creating alsa driver ... hw:0|hw:0|128|2|48000|0|0|nomon|swmeter|-|32bit
>> 
>> configuring for 48000Hz, period = 128 frames (2.7 ms), buffer = 2 periods
>> 
>> ALSA: final selected sample format for capture: 32bit integer little-endian
>> 
>> ALSA: use 16 periods for capture
>> 
>> ALSA: final selected sample format for playback: 32bit integer little-endian
>> 
>> ALSA: use 16 periods for playback
>> 
>> 
>> - what are those "periods" in the ALSA lines? (2 for the PC and 16 for the
>> BBB) ? I read a post by Jeremy Jongepier about the Cubieboard2 stating that
>> the hardcoded values for the Cubie (Minimum number of periods was 4 and
>> minimum buffer size was 1024) where unfit for realtime operation. Why is
>> that so?
> 
> Hello Gianfranco,
> 
> What kind of audio interface are you using with the BBB? I'm no ALSA
> expert but it seems as if the minimum period size of the driver has been
> set to 16. If you have access to the source code of the driver you could
> experiment with lower default values for .period_bytes_min and .periods_min.
> 
> Bye,
> 
> Jeremy
> 
> _______________________________________________
> Linux-audio-dev mailing list
> Linux-audio-dev at lists.linuxaudio.org
> http://lists.linuxaudio.org/listinfo/linux-audio-dev