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

From: Mathis Richter
Subject: [Discuss-gnuradio] Edirol UA-25 24-bit recording
Date: Mon, 25 Feb 2008 12:00:22 +0000
User-agent: Mutt/1.5.17+20080114 (2008-01-14)


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:

# 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))

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):

PCM name: hw:1,0
Access types:
    MMAP_COMPLEX         NO
    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

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?

I should mention that I'm running the latest gnuradio development code
from subversion (updated last night) on Debian Sid.

Best regards,

Mathis Richter <address@hidden>
GnuPG Fingerprint: 5069 3C27 0178 D542 DFB4 04F6 29BD 9EF2 1BE0 DDF6

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