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

[Eric Blossom]

On Mon, Feb 25, 2008 at 12:00:22PM +0000, Mathis Richter wrote:
> Hello
> 
> I'm new on this list. I'm working on a radio orienteering project for a
> university course and we are using gnuradio for signal analysis.
> 
> I'm trying to get the Edirol UA-25 (USB sound card) to work with
> gnuradio. My test program currently looks like this:
> 
> ---snip---
> # UA-25 as audio source
> src0 = audio.source (96000, "hw:1,0");
> # laptop on-board sound card as destination
> dst = audio.sink (44100, "hw:0,0")
> # connect them
> fg.connect ((src0, 0), (dst, 0))
> ---snap---
> 
> This works just fine when using 16-bit and a sampling rate of 44.1kHz on
> the UA-25, but I will need 24 bits (with 96kHz). Those settings produce
> the following error however (verbose output):
> 
> ---snip---
> PCM name: hw:1,0
> Access types:
>     MMAP_INTERLEAVED     YES
>     MMAP_NONINTERLEAVED  NO
>     MMAP_COMPLEX         NO
>     RW_INTERLEAVED       YES
>     RW_NONINTERLEAVED    NO
> Formats:
>     S24_3LE              YES
> Number of channels
>     min channels: 2
>     max channels: 2
>     2 channels  YES
> Sample Rates:
>     min rate:   96000 (dir = 0)
>     max rate:   96000 (dir = 0)
>       8000  NO
>      16000  NO
>      22050  NO
>      32000  NO
>      44100  NO
>      48000  NO
>      96000  YES
>     192000  NO
> audio_alsa_source[hw:1,0]: failed to find acceptable format
> Traceback (most recent call last):
>   File "./ardf.py", line 37, in ?
>     fg = build_graph ()
>   File "./ardf.py", line 19, in build_graph
>     src0 = audio.source (96000, "hw:1,0");
>   File "/usr/local/lib/python2.4/site-packages/gnuradio/audio_alsa.py", line 
> 219, in source
>     return _audio_alsa.source(*args)
> RuntimeError: audio_alsa_source
> ---snap---
> 
> I tried understanding what the problem was, but wasn't able to figure it
> out. audio_source_alsa seems to not be able to set the sample format
> (S24_3LE?) and it seems that audio_source_alsa.cc specifies only S16 and
> S32 as acceptable sample formats.
> I'm guessing that audio_source_alsa supports 24-bit samples, so does
> anybody have an idea what I'm doing wrong?

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.

  http://gnuradio.org/trac/wiki/PatchSubmissionGuidelines


Let me know if you need more of a clue, and I'll take a look at the
code.

Thanks,
Eric