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[Discuss-gnuradio] Problem with 192KHz sampling rate on alsa source
From: |
Marcus D. Leech |
Subject: |
[Discuss-gnuradio] Problem with 192KHz sampling rate on alsa source |
Date: |
Tue, 28 Dec 2010 17:14:00 -0500 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101103 Fedora/1.0-0.33.b2pre.fc14 Thunderbird/3.1.6 |
I'm running Fedora 14, with the latest Gnu Radio code.
I have an M-Audio Revolution 7.1 sound card, which can sample up to 192KHz.
I have a flow-graph that sets the card up for 192KHz sampling, and I've
confirmed that the hardware apparently thinks it's sampling
at 192KHz, but when I display the FFT of the resulting sample stream,
the spectrum is "mirrored" about 48KHz, almost as if something,
somewhere, is running at the wrong sample rate, but I can't figure
out *where* that might be.
Do I have to do anything special to pulseaudio configuration to get
support for the 192KHz rate? This particular card uses the Envy24HT
(ICE1724) chipset:
Here's the hw_params file from /proc/asound for the card in question:
access: RW_INTERLEAVED
format: S32_LE
subformat: STD
channels: 2
rate: 192000 (192000/1)
period_size: 1920
buffer_size: 7680
This is a 24-bit card, which means that the driver is using S32_LE --
does that confuse Gnu Radio Alsa source? Is it expecting 16-bit samples,
and mis-interpreting the 32-bit samples it's getting?
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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