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minimodem carrier detect

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This commit is contained in:
Kamal Mostafa 2011-05-25 17:02:50 -07:00
parent 4aa97884c4
commit 9e4ad3a2f7
1 changed files with 17 additions and 20 deletions
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37
src/minimodem.c
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@ -237,41 +237,37 @@ reprocess_audio:
float msdelta = mag_mark - mag_space; float msdelta = mag_mark - mag_space;
#define TRICK_DETECT ( 0.5 * MAX(mag_mark,mag_space) )
// Detect carrier #define CD_MIN_TONEMAG 0.001
float mag_detect = 0.001; #define CD_MIN_MSDELTA_RATIO 0.5
unsigned char carrier_detect =
mag_mark + mag_space > mag_detect /* Detect bfsk carrier */
int carrier_detect /*boolean*/ =
mag_mark + mag_space > CD_MIN_TONEMAG
&& &&
fabs(msdelta) >= TRICK_DETECT; fabs(msdelta) > CD_MIN_MSDELTA_RATIO * MAX(mag_mark, mag_space);
#ifdef TRICK #ifdef TRICK
// EXCELLENT trick -- fixes 300 baud perfectly // EXCELLENT trick -- fixes 300 baud perfectly
// shift the input window if the msdelta is small // shift the input window if the msdelta is small
static unsigned int skipped_frames = 0; static unsigned int skipped_frames = 0;
if ( carrier_detected && fabs(msdelta) < TRICK_DETECT ) if ( ! carrier_detect )
{ {
# if 0
skipped_frames++;
if ( skipped_frames >= nsamples ) // maybe nsamples/2 ??
nframes = 0;
else
nframes = 1;
printf( "*" );
# else
if ( nframes == nsamples ) { if ( nframes == nsamples ) {
#if 0
// nframes = nsamples / 2; // nframes = nsamples / 2;
// nframes = nsamples / 16; // shift by 1/4 the bit width nframes = nsamples / 4; // shift by 1/4 the bit width
nframes = 1;
nframes = nframes ? nframes : 1; nframes = nframes ? nframes : 1;
#else
nframes = 1;
#endif
} }
skipped_frames += nframes; skipped_frames += nframes;
if ( skipped_frames >= nsamples ) // maybe nsamples/2 ?? if ( skipped_frames >= nsamples ) // maybe nsamples/2 ??
nframes = 0; nframes = 0;
# endif
if ( nframes ) { if ( nframes ) {
size_t nbytes = nframes * pa_framesize; size_t nbytes = nframes * pa_framesize;
size_t reuse_bytes = nsamples*pa_framesize - nbytes; size_t reuse_bytes = nsamples*pa_framesize - nbytes;
@ -287,7 +283,7 @@ reprocess_audio:
} }
} }
if ( textscope ) { if ( carrier_detect && textscope ) {
if ( skipped_frames ) if ( skipped_frames )
printf( "<skipped %u (of %u) frames>\n", printf( "<skipped %u (of %u) frames>\n",
skipped_frames, nsamples); skipped_frames, nsamples);
@ -298,6 +294,7 @@ reprocess_audio:
unsigned char bit; unsigned char bit;
if ( carrier_detect ) if ( carrier_detect )
{ {
bit = signbit(msdelta) ? 0 : 1; bit = signbit(msdelta) ? 0 : 1;
@ -335,7 +332,7 @@ reprocess_audio:
} }
if ( ! carrier_detected ) if ( ! carrier_detected )
printf( "###CARRIER###\n"); printf( "###CARRIER###\n");
carrier_detected = carrier_detect; carrier_detected = carrier_detect;
if ( textscope ) { if ( textscope ) {