fsk cleanup
This commit is contained in:
Kamal Mostafa
parent
5f538ed54d
commit
71baa6f916
86
src/fsk.c
86
src/fsk.c
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@ -162,7 +162,7 @@ fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
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unsigned int bit_nsamples = (float)(samples_per_bit + 0.5);
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// 0123456789A
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// isddddddddp i == idle bit (a.k.a. previous stop bit)
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// isddddddddp i == idle bit (a.k.a. prev_stop bit)
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// s == start bit
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// d == data bits
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// p == stop bit
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@ -251,6 +251,7 @@ fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
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*bits_outp = best_bits;
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*frame_start_outp = best_t;
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/* The confidence equation */
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float confidence = best_v / fskp->n_frame_bits;
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debug_log("FSK_FRAME datum='%c' (0x%02x) c=%f t=%d\n",
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@ -273,9 +274,6 @@ fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
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int
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main( int argc, char*argv[] )
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{
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int ret = 1;
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if ( argc < 2 ) {
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fprintf(stderr, "usage: fsk [filename] baud_rate [ mark_hz space_hz ]\n");
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return 1;
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@ -344,15 +342,9 @@ main( int argc, char*argv[] )
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/*
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* Run the main loop
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* Prepare the fsk plan
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*/
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ret = 0;
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fsk_plan *fskp = fsk_plan_new(sample_rate,
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bfsk_mark_f, bfsk_space_f,
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band_width, 8);
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@ -362,6 +354,11 @@ main( int argc, char*argv[] )
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return 1;
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}
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/*
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* Run the main loop
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*/
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int ret = 0;
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size_t fill_nsamples = nsamples_per_bit * 12;
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@ -375,6 +372,7 @@ main( int argc, char*argv[] )
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unsigned int nbytes_decoded = 0;
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int carrier = 0;
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unsigned int noconfidence = 0;
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while ( 1 ) {
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debug_log( "@read samples+%ld n=%lu\n",
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@ -385,43 +383,54 @@ main( int argc, char*argv[] )
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// carrier_nsamples += read_nsamples;
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debug_log( "--------------------------\n");
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// FIXME: explain
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unsigned int frame_nsamples = nsamples_per_bit * 11;
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unsigned int bits = 0;
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// FIXME: explain
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unsigned int try_max_nsamples = nsamples_per_bit;
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// FIXME: explain
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unsigned int try_step_nsamples = nsamples_per_bit / 4;
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if ( try_step_nsamples == 0 )
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try_step_nsamples = 1;
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debug_log( "--------------------------\n");
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unsigned int t = 0;
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float confidence;
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unsigned int bits = 0;
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/* Note: frame_start_sample is actually the sample where the
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* prev_stop bit begins (since the "frame" includes the prev_stop). */
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unsigned int frame_start_sample = 0;
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confidence = fsk_find_frame(fskp, samples, frame_nsamples,
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/*try_max_nsamples*/ nsamples_per_bit,
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try_max_nsamples,
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try_step_nsamples,
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&bits,
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&t
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&frame_start_sample
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);
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#define FSK_MIN_CONFIDENCE 0.41
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// #define FSK_MIN_CONFIDENCE 0.13
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unsigned int advance;
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if ( confidence <= FSK_MIN_CONFIDENCE ) {
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if ( carrier ) {
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if ( ++noconfidence > 3 ) // FIXME: explain
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{
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fprintf(stderr, "### NOCARRIER nbytes=%u confidence=%f ###\n",
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nbytes_decoded,
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confidence_total / nbytes_decoded );
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nbytes_decoded, confidence_total / nbytes_decoded );
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carrier = 0;
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confidence_total = 0;
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nbytes_decoded = 0;
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}
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}
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t = nsamples_per_bit;
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/* Advance the sample stream forward by try_max_nsamples so the
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* next time around the loop we continue searching from where
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* we left off this time. */
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advance = try_max_nsamples;
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} else {
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@ -431,20 +440,32 @@ debug_log( "--------------------------\n");
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}
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confidence_total += confidence;
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nbytes_decoded++;
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noconfidence = 0;
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// t += nsamples_per_bit * 10;
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t += nsamples_per_bit * 9.5;
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debug_log( "@ t=%u\n", t);
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/* Advance the sample stream forward past the decoded frame
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* but not past the stop bit, since we want it to appear as
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* the prev_stop bit of the next frame, so ...
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*
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* advance = 1 prev_stop + 1 start + 8 data bits == 10 bits
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*
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* but actually advance just a bit less than that to allow
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* for clock skew, so ...
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*
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* advance = 9.5 bits */
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advance = frame_start_sample + nsamples_per_bit * 9.5;
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debug_log( "@ frame_start=%u advance=%u\n", frame_start_sample, advance);
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char the_byte = isprint(bits)||isspace(bits) ? bits : '.';
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printf( "%c", the_byte );
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fflush(stdout);
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}
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}
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memmove(samples, samples+t, (fill_nsamples-t)*sizeof(float));
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read_bufptr = samples + (fill_nsamples-t);
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read_nsamples = t;
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memmove(samples, samples+advance,
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(fill_nsamples-advance)*sizeof(float));
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read_bufptr = samples + (fill_nsamples-advance);
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read_nsamples = advance;
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assert ( read_nsamples <= buf_nsamples );
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assert ( read_nsamples > 0 );
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@ -454,6 +475,11 @@ debug_log( "--------------------------\n");
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if ( ret != 0 )
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fprintf(stderr, "simpleaudio_read: error\n");
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if ( carrier ) {
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fprintf(stderr, "### NOCARRIER nbytes=%u confidence=%f ###\n",
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nbytes_decoded, confidence_total / nbytes_decoded );
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}
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simpleaudio_close(sa);
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fsk_plan_destroy(fskp);
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