J. Lance Cotton wrote:
I am trying to get soundmodem (usermode) working with a Soundblaster
Live card on SuSE 9.3 and the commercial OSS driver.
The problem is that apparently the SB card supports only 8k, 11.025k,
12k, ... sampling rates. At 1200bps AFSK, soundmodem demodulator asks
for (or gets) 9600Hz sampling rate.
Something, as far as I can tell, is opening the soundcard for recording
at 9600Hz sample rate, but I've been told that that rate isn't supported
by my SB Live card. I thought that in that instance, the "next closest"
rate would be returned instead...
I do not know if this is a problem with the Commercial OSS driver, the
SB Live card, or soundmodem. I've tried editing the soundcard/audioio.c
file to "force" other sample rates. It does open the card at the forced
rate, but the decoding still doe not work reliably. (The problem is
exemplified in the samples I recorded and put at
http://www.cmsworldwide.com/Files/soundsamples/index.html )
**Question: Is there any official way to have soundmodem request a
user-custom sampling rate? Like a hidden config?
Thanks. 73 KJ5O
I came across a similar thing. Looking at the soundmodemconfig scope
function I saw horizontal lines in the waveform - this is clearly
impossible for an AC coupled signal so I suspected that 9600 was not a
valid sample rate for my audio codec. Here is what I did to fix it:
in line 233 of soundcard/main.c change
unsigned int samplerate = 5000, mode;
to
unsigned int samplerate = 11025, mode;
then in line 710 of configapp/src/diag.c change
diagstate.samplerate = 5000;
to
diagstate.samplerate = 11025;
Even though the sample rate is set to 5000 there is a selection routine
in audioio.c that steps it up to 9600. I tried editing the valid sample
rate list there but it still used 9600.
After making the above changes I have not had any trouble at all with
soundmodem. Not that there aren't any, but I don't know of another way
to force a sample rate.
Hope this helps.
Dave
AD5OO
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