Re: [Discuss-gnuradio] Increasing ALSA Sampling Rate

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<ra@websterling.com> 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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