I’d noticed a problem with running the M-Audio Revolution 7.1 sound card
at 192KHz as a source in Gnu Radio – the spectrum was
all “funny”, with the spectrum getting “reflected” about 48KHz,
almost as if the actual sample rate on the card wasn’t correct, and
perhaps set to 96KHz instead of the expected 192KHz.
To eliminate Gnu Radio as a cause, I used “arecord” with the correct
parameters to record a 20-second chunk of audio from the card,
then used Gnu Radio to plot the spectrum. Sure enough, the spectrum
is still not correct, so I suspect this is a driver issue.
I know that I used to be able to use this card at 192KHz several years
ago, and the card advertises 192KHz sampling as a feature.
–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
On 12/30/2010 03:31 PM, Marcus D. Leech wrote:
I know that I used to be able to use this card at 192KHz several
years ago, and the card advertises 192KHz sampling as a feature.
Yet another follow-up.
It turns out that despite what the hardware reports, the ADC on the
Revolution 7.1 only runs at 96KHz, and the controller apparently does
some kind of half-assed upsampling. Gack!
–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
On 12/30/2010 07:52 PM, Rafael D. wrote:
Have you tried the OSS driver, using the 4front drivers?
Best regards,
Rafael D.
I dug deeper, and the card apparently only supports 96KHz on the input
side. I haven’t used the
card in a few years, so my recollection of its input-side rate must be
wrong.
–
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
Have you tried the OSS driver, using the 4front drivers?
Best regards,
Rafael D.