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FM Demodulator fixes

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was an implicit float to int in the primary filter cutoff value causing
distortion.
This commit is contained in:
Charles J. Cliffe 2014-11-12 19:09:22 -05:00
parent adc6fcce85
commit 02cd0f6516
1 changed files with 5 additions and 5 deletions
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10
src/Demodulator.cpp
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@ -41,9 +41,9 @@ static int patestCallback(const void *inputBuffer, void *outputBuffer, unsigned
Demodulator::Demodulator() { Demodulator::Demodulator() {
bandwidth = 300000; bandwidth = 200000;
resample_ratio = (float) (bandwidth) / (float) SRATE; resample_ratio = (float) (bandwidth) / (float) SRATE;
wbfm_frequency = 32000; wbfm_frequency = 100000;
wbfm_resample_ratio = (float) (wbfm_frequency) / (float) bandwidth; wbfm_resample_ratio = (float) (wbfm_frequency) / (float) bandwidth;
audio_frequency = 48000; audio_frequency = 48000;
audio_resample_ratio = (float) (audio_frequency) / (float) wbfm_frequency; audio_resample_ratio = (float) (audio_frequency) / (float) wbfm_frequency;
@ -93,7 +93,7 @@ Demodulator::Demodulator() {
std::cout << "\tPortAudio error: " << Pa_GetErrorText(err) << std::endl; std::cout << "\tPortAudio error: " << Pa_GetErrorText(err) << std::endl;
} }
float fc = 0.5f * (bandwidth / SRATE); // filter cutoff frequency float fc = 0.5f * ((float)bandwidth / (float)SRATE) * 0.75; // filter cutoff frequency
float ft = 0.05f; // filter transition float ft = 0.05f; // filter transition
float As = 60.0f; // stop-band attenuation [dB] float As = 60.0f; // stop-band attenuation [dB]
float mu = 0.0f; // fractional timing offset float mu = 0.0f; // fractional timing offset
@ -106,7 +106,7 @@ Demodulator::Demodulator() {
fir_filter = firfilt_crcf_create(h, h_len); fir_filter = firfilt_crcf_create(h, h_len);
h_len = estimate_req_filter_len(ft, As); h_len = estimate_req_filter_len(ft, As);
liquid_firdes_kaiser(h_len, 0.3f, As, mu, h); liquid_firdes_kaiser(h_len, 32000.0/(float)wbfm_frequency, As, mu, h);
fir_audio_filter = firfilt_crcf_create(h, h_len); fir_audio_filter = firfilt_crcf_create(h, h_len);
@ -120,7 +120,7 @@ Demodulator::Demodulator() {
audio_resampler = msresamp_crcf_create(audio_resample_ratio, As); audio_resampler = msresamp_crcf_create(audio_resample_ratio, As);
msresamp_crcf_print(audio_resampler); msresamp_crcf_print(audio_resampler);
float kf = 0.5f; // modulation factor float kf = 0.75; // modulation factor
fdem = freqdem_create(kf); fdem = freqdem_create(kf);
freqdem_print(fdem); freqdem_print(fdem);