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Re: [Discuss-gnuradio] Increasing ALSA Sampling Rate

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] Increasing ALSA Sampling Rate
Date: Mon, 31 Jan 2011 10:30:58 -0500

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

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.


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