Re: [Discuss-gnuradio] Increasing ALSA Sampling Rate

[George S. Williams]

Hey, Tom,

Thanks for the reply. I'm not sure that it's entirely an ALSA problem.

Both my aplay and snd-bt88x are patched to allow 1792000. If I do-
arecord -D hw:1,1 -r 1792000 -f S16_LE -t wav -d 5 test0.wav

I get-
Recording WAVE 'test0.wav' : Signed 16 bit Little Endian, Rate 1792000 
Hz, Mono

And- soxi reports-
Input File     : 'test0.wav'
Channels       : 1
Sample Rate    : 1.792e+06
Precision      : 16-bit
Duration       : 00:00:05.00 = 8960000 samples ~ 375 CDDA sectors
Sample Encoding: 16-bit Signed Integer PCM

So it looks to me like ALSA recorded at 1792000.

Wish I knew more about ALSA and gnuradio- probably will before it's over.

George



On 1/31/2011 10:30 AM, Tom Rondeau wrote:
> On Thu, Jan 27, 2011 at 11:38 AM, George S. Williams<address@hidden>  wrote:
> > Is it possible to increase the maximum sampling rate for audio_alsa?
> >
> > I am experimenting with using a modified TV tuner card as an ADC. The card
> > uses a Bt878a chipset. arecord can record from the card at 1972000 rate and
> > GRC shows the maximum rate as 1972000, but GNUradio can only sample at
> > 896000.
> >
> > Running GNUradio at 1972000 rate gives the following error-
> >
> >
> > audio_alsa_source[hw:2,1]: get_period_size failed: Invalid argument
> > Traceback (most recent call last):
> >   File "/root/top_block.py", line 81, in<module>
> >     tb = top_block()
> >   File "/root/top_block.py", line 49, in __init__
> >     self.audio_source_0 = audio.source(samp_rate, "hw:2,1", True)
> >   File "/usr/local/lib/python2.6/site-packages/gnuradio/audio_alsa.py", line
> > 241, in source
> >     return _audio_alsa.source(*args, **kwargs)
> > RuntimeError: audio_alsa_source
> >
> >
> > Is there some setting change that can enable the 1792000 rate?
> >
> > Thanks,
> > George
>
>
> George,
> It appears that this error is occurring in the ALSA asound library
> itself (see line 205 of gr-audio-alsa/src/audio_alsa_source.cc). I
> haven't spent much time looking around the alsa implementation, so I
> can't say for certain, but this appears to be a problem with ALSA, not
> GNU Radio.
>
> Hopefully, someone else with much more knowledge about ALSA and it's
> capabilities can tell you better.
>
> Tom
>
>
>
>
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