minimodem fixed black magic
This commit is contained in:
Kamal Mostafa
parent
cbb4f6a242
commit
a5492bbc6a
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@ -74,6 +74,7 @@ int main(int argc, char*argv[]) {
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unsigned int sample_rate = ss.rate;
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unsigned int band_width = decode_rate / 2;
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// unsigned int band_width = decode_rate;
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unsigned int bfsk_mark_band = (bfsk_mark_f +(float)band_width/2) / band_width;
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unsigned int bfsk_space_band = (bfsk_space_f +(float)band_width/2) / band_width;
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@ -146,7 +147,14 @@ int main(int argc, char*argv[]) {
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* Prepare the input sample chunk rate
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*/
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int nsamples = sample_rate / decode_rate;
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nsamples -= 1; // BLACK MAGIC!
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#if 1
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/* BLACK MAGIC! Run the decoder 1% slow ... */
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int nsamples_speedup = nsamples * 0.01;
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if ( nsamples_speedup == 0 )
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nsamples_speedup = 1;
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nsamples += nsamples_speedup; // BLACK MAGIC!
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#endif
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// float magscalar = 1.0 / (fftsize/2.0); /* normalize fftw output */
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float magscalar = 1.0 / (nsamples/2.0); /* normalize fftw output */
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@ -158,6 +166,7 @@ int main(int argc, char*argv[]) {
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magscalar /= 2.0;
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float actual_decode_rate = (float)sample_rate / nsamples;
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fprintf(stderr, "### nsamples=%u ", nsamples);
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fprintf(stderr, "### baud=%.2f mark=%u space=%u ###\n",
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actual_decode_rate,
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bfsk_mark_band * band_width,
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@ -172,6 +181,9 @@ int main(int argc, char*argv[]) {
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unsigned int bfsk_bits = 0xFFFFFFFF;
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unsigned char carrier_detected = 0;
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unsigned long long carrier_nsamples = 0;
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unsigned long long carrier_nsymbits = 0;
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ret = 0;
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while ( 1 ) {
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@ -238,7 +250,7 @@ reprocess_audio:
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float msdelta = mag_mark - mag_space;
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#define CD_MIN_TONEMAG 0.001
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#define CD_MIN_TONEMAG 0.1
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#define CD_MIN_MSDELTA_RATIO 0.5
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/* Detect bfsk carrier */
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@ -250,23 +262,29 @@ reprocess_audio:
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#ifdef TRICK
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// EXCELLENT trick -- fixes 300 baud perfectly
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// shift the input window if the msdelta is small
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// shift the input window to "catch up" if the msdelta is small
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static unsigned int skipped_frames = 0;
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if ( ! carrier_detect )
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{
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if ( nframes == nsamples ) {
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#if 0
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// nframes = nsamples / 2;
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nframes = nsamples / 4; // shift by 1/4 the bit width
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#if 1
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/* shift by 1/2 the width of one data bit */
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// any of these work ...
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// nframes = nsamples / 2;
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nframes = nsamples / 4;
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// nframes = nsamples / 8;
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// nframes = nsamples / 16;
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// nframes = 1;
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nframes = nframes ? nframes : 1;
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#else
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nframes = 1;
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#endif
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}
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skipped_frames += nframes;
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if ( skipped_frames >= nsamples ) // maybe nsamples/2 ??
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// clamp the shift to half the bit width
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if ( skipped_frames + nframes > nsamples/2 )
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nframes = 0;
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else
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skipped_frames += nframes;
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if ( nframes ) {
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size_t nbytes = nframes * pa_framesize;
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@ -285,11 +303,10 @@ reprocess_audio:
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if ( carrier_detect && textscope ) {
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if ( skipped_frames )
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printf( "<skipped %u (of %u) frames>\n",
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fprintf(stderr, "<skipped %u (of %u) frames>\n",
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skipped_frames, nsamples);
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}
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skipped_frames = 0;
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#endif
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unsigned char bit;
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@ -297,6 +314,9 @@ reprocess_audio:
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if ( carrier_detect )
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{
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// carrier_nsamples += nsamples + skipped_frames;
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carrier_nsamples += nsamples - skipped_frames;
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carrier_nsymbits++;
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bit = signbit(msdelta) ? 0 : 1;
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#if 0
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@ -314,6 +334,8 @@ reprocess_audio:
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else
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bit = 1;
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skipped_frames = 0;
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lastbit = bit;
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// save 11 bits:
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@ -325,14 +347,23 @@ reprocess_audio:
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if ( ! carrier_detect )
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{
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if ( carrier_detected ) {
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printf( "###NOCARRIER###\n");
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float samples_per_bit =
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(float)carrier_nsamples / carrier_nsymbits;
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float rx_baud_rate =
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(float)sample_rate / samples_per_bit;
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fprintf(stderr, "###NOCARRIER (bits=%llu rx=%.2f baud) ###\n",
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carrier_nsymbits,
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rx_baud_rate);
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carrier_detected = 0;
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}
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continue;
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}
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if ( ! carrier_detected )
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printf( "###CARRIER###\n");
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if ( ! carrier_detected ) {
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fprintf(stderr, "###CARRIER###\n");
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carrier_nsamples = 0;
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carrier_nsymbits = 0;
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}
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carrier_detected = carrier_detect;
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if ( textscope ) {
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@ -356,12 +387,16 @@ reprocess_audio:
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for ( i=15; i>=0; i-- )
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printf("%c", bfsk_bits & (1<<i) ? '1' : '0');
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printf(" ");
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fflush(stdout);
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}
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if ( ! carrier_detected ) {
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if ( textscope )
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if ( textscope ) {
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printf("\n");
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fflush(stdout);
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}
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continue;
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}
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// stop--- v v--- start bit
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@ -371,12 +406,23 @@ reprocess_audio:
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unsigned char byte = ( bfsk_bits >> 2) & 0xFF;
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if ( textscope )
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printf("+");
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if ( byte == 0xFF ) {
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if ( textscope )
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printf("idle");
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} else {
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printf("%c", isspace(byte)||isprint(byte) ? byte : '.');
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fflush(stdout);
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}
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bfsk_bits = 1 << 10;
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}
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if ( textscope )
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if ( textscope ) {
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printf("\n");
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fflush(stdout);
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}
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}
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