[LAU] recording with firewire device and webcam / alsa and freebob together

Robin Gareus robin at gareus.org
Sun Jun 29 19:14:35 EDT 2008

Nick Urban wrote:
> Hello,
> I just joined the list, so I hope this is the right place for this question..
> I have a M-Audio Firewire solo which I use with jack and firebob to
> record audio.
> I was thinking about making a little video with my Quickcam 9000 Pro,
> but because the audio quality of its built-in mic is poor, I wanted to
> use my nice studio mic instead. I am currently using guvcview to
> record with the camera, and it has a selection of input options, on
> which, when jack is running, an extra option appears: "system". I
> thought, wow, maybe this actually supports jack! But when I try using
> that option it just crashes. Oh well, I didn't expect that to work
> anyway.

Welcome Nick.

If you can reproduce this with guvcview while recording with other
software works, you should report this on the Forum of guvcview or check
their Wiki for the problem - it might be easy to solve. I don't know
much about guvcview but I'm not aware that luvcview has JACK support.
I'm gonna check out the latest version now ;)

> But I thought, okay, maybe I can set up a virtual ALSA device that
> somehow connects to jack. Then I could record for that device, which
> would actually just be a jack sink (which I would have connected my
> mic input to). I can't figure out any way to do that, though. I
> searched around for ALSA jack clients, couldn't find anything. I tried
> running two different jack instances (one with alsa, one with
> freebob), but they didn't seem to be aware of each other when I looked
> at the connections panel in qjackctl.
> Does anyone have any suggestions here? 

You can try gstreamer. I once toyed around with it and got a
jack-audio-port recording in sync with a v4l usb webcam @30fps with a
simple gstreamer pipeline. It's quite straight forward: you use
'gstreamer-properties' to set up your audio and video devices and check
the gstreamer-wiki on how to make a recording eg:

In my experience gstreamer is the quickest solution, but there are
plenty of alternatives, depending on where and how far you want to go:
As you mentioned ffmpeg or maybe guvcview should work using a
virtual-JACK-ALSA device setup in $HOME/.asoundrc - see:

or you might even be able to fire up http://lives.sf.net/ which has JACK
support, or use a puredata+gem patch to do the trick..

> Another reason I'd like jack
> and ALSA to play together is so that I can use my speakers (which are
> connected to my PCI sound card) to play audio from Ardour while I am
> working on takes with my firewire interface.

Every reason to use JACK is a good one, but this is an exception ;) You
can not use two sound-cards in the same jack-server at the same time
[unless you resample with netjack's alsa_in/out].
You could run two independent jack-servers, but they can not share any
clients or I/O ports.


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