Re: [Discuss-gnuradio] Edirol UA-25 24-bit recording

[Eric Blossom]

On Tue, Feb 26, 2008 at 01:07:14AM +0000, Mathis Richter wrote:
> On 2008-02-25 14:10, Eric Blossom wrote:
> > The code doesn't support S24_3LE because when we wrote it, we didn't
> > have any cards that used that format, and it wasn't obvious (to me)
> > exactly how the format was represented.  It would be great if you
> > could sort this out and submit a patch with the fix.
> 
> As much as I would like to do that, I don't know enough about it all.
> Looking around a bit to see whether I could figure something out, I soon
> got stuck...
> I then tried to use the .asoundrc file to convert the incoming signal
> into a different format, but no luck there either.
> 
> > Let me know if you need more of a clue, and I'll take a look at the
> > code.
> 
> Any help would be greatly appreciated! I will be working on this during
> the next couple of days.
> 
> Thanks,
> Matt

Hi Matt,

The code that needs to be modified is in
gr-audio-alsa/src/audio_alsa_sink.cc and audio_alsa_source.cc

If you look at either piece of code, you'll see that there's a
work_s16, work_s32, work_s16_1x2, work_s32_1x2.  What you'd need to
provide is the corresponding work_s24 and work_s24_1x2.  The *_1x2
versions are used to force mono data into stereo format to account for
cards that only handle two channels.  I think if you look at the code,
you'll find that it shouldn't be too tricky... and you've got a sound
card which you can test it on!

Please give it a try!

Eric