discuss-gnuradio
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [Discuss-gnuradio] New gr-audio-jack module


From: Clark Pope
Subject: RE: [Discuss-gnuradio] New gr-audio-jack module
Date: Mon, 03 Oct 2005 08:56:57 -0400

This post reminded me of a question I had: Has anyone developed a network source/sink? Basically a module just like the audio sink but who's sole job is to package and stream the data to a network destination. With the network source/sink in place one could listen to the audio remotely and do some simple distributed computing, i.e. if one PC isn't enough to do your signal processing you can have 3 or 4 or 5 PCs working on the same flow graph.

----Original Message Follows----
From: Stephane Fillod <address@hidden>
To: gnuradio mailing list <address@hidden>
Subject: [Discuss-gnuradio] New gr-audio-jack module
Date: Mon, 3 Oct 2005 09:35:52 +0200

Gang,

You will find at savannah a new GNU Radio module: gr-audio-jack.
This is both source and sink modules for JACK http://jackit.sourceforge.net.
The JACK Audio Connection Kit is a low-latency sound server. JACK allows
the connection of multiple applications to an audio device, as well as
allowing them to share audio between themselves. It shows handy when you
were connecting previously an external patch cord between the line-out
and line-in of your sound card. With JACK, this is all done by software.

To initally check it out:

$ cvs -z3 -d:ext:address@hidden:/cvsroot/gnuradio co -P gr-audio-jack

It has been tested with libjack-0.100 under Debian, with a USRP/TVRX.
There's a screenshot here http://f8cfe.free.fr/ham/gnuradio/jack_wfm.png
Here was the plumbing:

        tvrx_wfm_rcv_gui.py (tuned to Canal B FM 94.0MHz)
                gr_sink
                   |
                   v
                copy_in
        audio_copy.py -i copy_in -o copy_out
                copy_out
                 /    \
                |      |
                v      v
alsa_pcm:playback_1   alsa_pcm:playback_2
        jackd           jackd

tvrx_wfm_rcv_gui.py was modified to use the audio_jack sink.
audio_copy.py was modified to use an audio_jack sink/source.
audio_copy.py was inserted just to exercice the audio_jack source.
The copy_out(mono) is connected to both playback_1&playback_2,
because alsa_pcm is a stereo device.

Just for the fun of it, I've added a Digital peak/Vu meter with the
following commands: "meterbridge -t dpm gr_sink:out"  and
"meterbridge -t vu gr_sink:out"  (from the meterbridge package
http://plugin.org.uk/meterbridge/).
So this adds gr_sink:out->meterbridge-13207 and ->meterbridge-13723.

JACK design is really nice. I recommand you to have a peek at it.
In the previous example, the patch bay is provided by qjackctl.
The only big drawback of JACK is that the sampling freq is fixed
within its domain (32kHz here, can be anything else). It is possible
to have more than one jackd running in parallel though.

One of my goal behind this gr-audio-jack module, is to be able to feed
legacy non-GNU Radio applications like gmfsk, Dream DRM receiver, DttSP,
etc., with signals from GNU Radio USRP. For that matter, I will need
a resampler. Can anyone recommand me a gr block to resample, say,
from 64kS/s to 48kS/s or directly the usrp source at 512kS/s to 48kS/s ?
Is the gr_rational_resampler finished?

IMHO, JACK enables interesting features, like being able to put a patch
cord somewhere in the flow graph for running a scope, without having to
change the source code of the running application. I'd love to see
that in GNU Radio. To be able to do that, we would need the Python
flowgraph to export its interface to other processes through RPC
(SUN's, IPC, sockets, pipes, etc.). To begin with, returning the current
flowgraph hierarchy and being able to make connections would be nice.
With proprer dressing, this would enable interface GNU Radio API from
Python/C++/etc..


Cheers
--
Stephane


_______________________________________________
Discuss-gnuradio mailing list
address@hidden
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/





reply via email to

[Prev in Thread] Current Thread [Next in Thread]