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SoftFM
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Reject IF sample rates 900kS/s or lower because RTL chip does not support it.

This commit is contained in:
Joris van Rantwijk 2014-01-05 17:02:40 +01:00
parent 7948164205
commit d1593544a4
1 changed files with 4 additions and 12 deletions
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16
main.cc
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@ -215,7 +215,7 @@ void usage()
"Usage: softfm -f freq [options]\n" "Usage: softfm -f freq [options]\n"
" -f freq Frequency of radio station in Hz\n" " -f freq Frequency of radio station in Hz\n"
" -d devidx RTL-SDR device index, 'list' to show device list (default 0)\n" " -d devidx RTL-SDR device index, 'list' to show device list (default 0)\n"
" -s ifrate IF sample rate in Hz (default 1000000)\n" " -s ifrate IF sample rate in Hz (default 1000000, min 900001)\n"
" -r pcmrate Audio sample rate in Hz (default 48000 Hz)\n" " -r pcmrate Audio sample rate in Hz (default 48000 Hz)\n"
" -M Disable stereo decoding\n" " -M Disable stereo decoding\n"
" -R filename Write audio data as raw S16_LE samples\n" " -R filename Write audio data as raw S16_LE samples\n"
@ -297,7 +297,8 @@ int main(int argc, char **argv)
devidx = -1; devidx = -1;
break; break;
case 's': case 's':
if (!parse_opt(optarg, ifrate) || ifrate <= 0) { // NOTE: RTL does not suppor sample rate 900 kS/s or lower
if (!parse_opt(optarg, ifrate) || ifrate <= 900000) {
badarg("-s"); badarg("-s");
} }
break; break;
@ -351,12 +352,6 @@ int main(int argc, char **argv)
exit(1); exit(1);
} }
if (3 * FmDecoder::default_bandwidth_if > ifrate) {
fprintf(stderr, "ERROR: IF sample rate must be at least %.0f Hz\n",
3 * FmDecoder::default_bandwidth_if);
exit(1);
}
// Catch Ctrl-C and SIGTERM // Catch Ctrl-C and SIGTERM
struct sigaction sigact; struct sigaction sigact;
sigact.sa_handler = handle_sigterm; sigact.sa_handler = handle_sigterm;
@ -372,10 +367,7 @@ int main(int argc, char **argv)
} }
// Intentionally tune at a higher frequency to avoid DC offset. // Intentionally tune at a higher frequency to avoid DC offset.
double tuner_freq = freq; double tuner_freq = freq + 0.25 * ifrate;
if (ifrate >= 5 * FmDecoder::default_bandwidth_if) {
tuner_freq += 0.25 * ifrate;
}
// Open RTL-SDR device. // Open RTL-SDR device.
RtlSdrSource rtlsdr(devidx); RtlSdrSource rtlsdr(devidx);