Re: [Jack-Devel] routing alsa through jack

On Sat, Jan 4, 2014 at 9:19 PM, Dominique Michel
<[hidden]> wrote:
> Le Fri, 3 Jan 2014 18:02:30 +0100,
> Kjetil Matheussen <[hidden]> a écrit :
>
>> I used this setup a while too, but it didn't work
>> very well. There was a latency on around a second,
>> and I also got some scratching noises now and then.
>>
>> So a while ago (still), I changed my .asoundrc file like this:
>>
>> pcm.rawjack {
>>     type jack
>>     playback_ports {
>>         0 system:playback_1
>>         1 system:playback_2
>>     }
>>     capture_ports {
>>         0 system:capture_1
>>         1 system:capture_2
>>     }
>> }
>>
>> pcm.jack {
>>     type plug
>>     slave { pcm "rawjack" }
>>     hint {
>>   description "JACK Audio Connection Kit"
>>     }
>> }
>>
>> pcm.!default {
>>     type plug
>>     slave { pcm "rawjack" }
>> }
>>
>>
>> And suddenly I got no noticable delay, no scratching
>> sounds now and then, and almost no trouble [1].
>>
>> What am I missing? Why run through the trouble
>> of setting up alsa_in, do the loop-thing, scripting,
>> and so forth?
>>
>> [1] Only trouble: I have to restart the chrome
>> browser after stopping and starting jack.
>
> Thank you! I didn't get the time to try it before now. You are the best.
>

Thanks for the kind words, but this is not exactly my invention. :-)
The jack alsa plugin is documented both at the alsa homepage
and at the jack homepage:

http://www.alsa-project.org/main/index.php/Asoundrc
http://jackaudio.org/routing_alsa
http://alsa.opensrc.org/Jack_(plugin)


Regarding this sentence at the jack homepage:

  "Some people have also found it quite buggy or unstable in some situations."

Perhaps this should be changed to "Some people in the past ...", or removed
completely. I also remember it was terribly buggy around 8 years ago (or so),
but it seems stable now.


And this sentence could also be a little bit misleading:

  "Note that this solution will create some latency: the ALSA JACK
plugin has to use a buffer between the data being sent by the
application and JACK itself to avoid clicks and dropouts."

This is of course true to other solutions as well (such as using the loop back
device or using the pulseaudio jack sink). Besides, the latency seems to have
been tweaked to be very small now. It can't be that many milliseconds
any longer.

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