[Jack-Devel] routing alsa through jack

Hello everybody,

I'm new here and I'm not a Jack developer, but I couldn't find any users 
mailing lists and this page [1] says that «If you're doing anything with jack, 
you need to be on this list», so I assumed users are welcome here...

I use Debian 64bit and I already have Jack working with my crappy integrated 
sound card. It samples mic input, it routes signal all around through the 
patchbay (qjackctl) and it plays the results in my headphones. Meanwhile it 
routes a copy to jack.record that saves all into a wav file, great.

Now I'd like to make a conference call with Skype (Alsa only, I don't want to 
add pulseaudio) and record it using my Jack toy. I need to record both mic and 
output, obviously.

After reading a few howtos, most of which seem too complicated for my needs 
(and in fact I can't manage to get a working configuration following them), I 
decided to roll my own solution, tailored at my needs.

My solution involves snd_aloop.

What I have already tried is to use snd_aloop, which gives 2 loop soundcards 
connected to each other, make Skype use hw:Loopback,0 for both input and 
output, then connect alsa_in and alsa_out to hw:Loopback,1 and add a few wires 
in the patchbay between alsa_in and my jack_mixer, then connect jack_mixer and 
alsa_out (the wire between jack_mixer and jack.record is already there).

The result is plain silence on the Skype side. Since Skype is not very 
friendly in telling users what's wrong, I decided to scrap it for the time 
being and use aplay for a test:

$ aplay -D hw:9 /usr/share/sounds/alsa/Front_Right.wav 
Playing WAVE '/usr/share/sounds/alsa/Front_Right.wav' : Signed 16 bit Little 
Endian, Rate 48000 Hz, Mono
aplay: set_params:1233: Sample format non available
Available formats:
- FLOAT_LE

then

$ aplay -f FLOAT_LE -D hw:9 /usr/share/sounds/alsa/Front_Right.wav 
Warning: format is changed to S16_LE
Playing WAVE '/usr/share/sounds/alsa/Front_Right.wav' : Signed 16 bit Little 
Endian, Rate 48000 Hz, Mono
aplay: set_params:1233: Sample format non available
Available formats:
- FLOAT_LE

So now I guess Skype is having similar problems. However before we dig into 
these problems, that might actually be off topic here, my question is: is my 
solution reasonable at all? Is it at all possible to route Alsa through Jack 
that way?

Thanks in advance fot any help.
Lucio.

[1] http://jackaudio.org/email

1387306286.29776_0.ltw:2, <2051731.ZIBsSLb7dx at fx>