kopia lustrzana https://github.com/windytan/slowrx
258 wiersze
6.3 KiB
C
258 wiersze
6.3 KiB
C
#include <stdlib.h>
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#include <math.h>
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#include <string.h>
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#include <fftw3.h>
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#include <gtk/gtk.h>
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#include <alsa/asoundlib.h>
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#include "common.h"
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/* Find the horizontal sync signal and adjust sample rate to cancel out any slant.
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* Length: number of PCM samples to process
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* Mode: one of M1, M2, S1, S2, R72, R36 ...
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* Rate: approximate sampling rate used
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* Skip: pointer to variable where the skip amount will be returned
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* returns adjusted sample rate
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*/
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double FindSync (unsigned int Length, int Mode, double Rate, int *Skip) {
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int LineWidth = ModeSpec[Mode].LineLen / ModeSpec[Mode].SyncLen * 4;
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// LineWidth = 400;
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unsigned int i, s, TotPix, xmax;
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double NextImgSample;
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double t=0, slantAngle;
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unsigned char SyncImg[700][630];
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int x,y,xmid,x0;
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unsigned short int xAcc[700] = {0};
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double Praw, Psync;
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unsigned char *HasSync;
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HasSync = malloc(Length * sizeof(char));
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if (HasSync == NULL) {
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perror("FindSync: Unable to allocate memory for sync signal");
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exit(EXIT_FAILURE);
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}
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memset(HasSync,0,Length * sizeof(char));
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unsigned short int lines[600][(MAXSLANT-MINSLANT)*2];
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unsigned short int cy, cx;
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int q, d, qMost, dMost;
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unsigned short int Retries = 0;
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int maxsy = 0;
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double Pwr[2048];
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// FFT plan
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fftw_plan Plan;
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double *in;
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double *out;
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unsigned int FFTLen = 1024;
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in = fftw_malloc(sizeof(double) * FFTLen);
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if (in == NULL) {
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perror("FindSync: Unable to allocate memory for FFT");
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free(HasSync);
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exit(EXIT_FAILURE);
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}
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out = fftw_malloc(sizeof(double) * FFTLen);
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if (out == NULL) {
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perror("FindSync: Unable to allocate memory for FFT");
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fftw_free(in);
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free(HasSync);
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exit(EXIT_FAILURE);
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}
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Plan = fftw_plan_r2r_1d(FFTLen, in, out, FFTW_FORWARD, FFTW_ESTIMATE);
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// Create 50-point Hann window
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double Hann[50];
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for (i = 0; i < 50; i++) Hann[i] = 0.5 * (1 - cos( 2 * M_PI * i / 49.0) );
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// Zero fill input array
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memset(in, 0, FFTLen * sizeof(in[0]));
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unsigned int LopassBin = GetBin(3000, FFTLen);
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printf("power est.\n");
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// Power estimation
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for (s = 0; s < Length; s+=50) {
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// Hann window
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for (i = 0; i < 50; i++) in[i] = PCM[s+i] * Hann[i];
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// FFT
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fftw_execute(Plan);
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// Power in the whole band
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Praw = 0;
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for (i=0;i<LopassBin;i++) {
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Pwr[i] = pow(out[i], 2) + pow(out[FFTLen-i], 2);
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Praw += Pwr[i];
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}
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Praw /= (FFTLen/2.0) * ( LopassBin/(FFTLen/2.0));
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// Power around the sync band
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i = GetBin(1200+HedrShift, FFTLen);
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Psync = (Pwr[i-1] + Pwr[i] + Pwr[i+1]) / 3.0;
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// If there is more than twice the amount of Power per Hz in the
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// sync band than in the rest of the band, we have a sync signal here
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if (Psync > 2*Praw) HasSync[s] = TRUE;
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else HasSync[s] = FALSE;
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for (i = 0; i < 50; i++) {
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if (s+i >= Length) break;
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HasSync[s+i] = HasSync[s];
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}
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}
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printf("hough\n");
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// Repeat until slant < 0.5° or until we give up
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while (1) {
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TotPix = LineWidth/2; // Start at the middle of the picture
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NextImgSample = 0;
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t = 0;
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maxsy = 0;
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x = y = 0;
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memset(SyncImg, 0, sizeof(SyncImg[0][0]) * LineWidth * 500);
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// Draw the sync signal into memory
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for (s = 0; s < Length; s++) {
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// t keeps track of time in seconds
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t += 1.0/Rate;
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if (t >= NextImgSample) {
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SyncImg[x][y] = HasSync[s];
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if (y > maxsy) maxsy = y;
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TotPix++;
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x++;
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if (x >= LineWidth) {
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y++;
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x=0;
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}
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NextImgSample += ModeSpec[Mode].LineLen / (1.0 * LineWidth);
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}
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}
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/** Linear Hough transform **/
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// zero arrays
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dMost = qMost = 0;
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memset(lines, 0, sizeof(lines[0][0]) * (MAXSLANT-MINSLANT)*2 * LineWidth);
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// Find white pixels
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for (cy = 0; cy < TotPix / LineWidth; cy++) {
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for (cx = 0; cx < LineWidth; cx++) {
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if (SyncImg[cx][cy]) {
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// Slant angles to consider
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for (q = MINSLANT*2; q < MAXSLANT*2; q ++) {
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// Line accumulator
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d = LineWidth + round( -cx * sin(deg2rad(q/2.0)) + cy * cos(deg2rad(q/2.0)) );
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if (d > 0 && d < LineWidth) {
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lines[d][q-MINSLANT*2] ++;
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if (lines[d][q-MINSLANT*2] > lines[dMost][qMost-MINSLANT*2]) {
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dMost = d;
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qMost = q;
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}
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}
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}
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}
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}
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}
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if ( qMost == 0) {
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printf(" no sync signal; giving up\n");
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break;
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}
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slantAngle = qMost / 2.0;
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//printf(" most (%d occurrences): d=%d q=%f\n", LineAcc[dMost][ (int)(qMost * 10) ], dMost, qMost);
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printf(" %.1f° (d=%d) @ %.2f Hz", slantAngle, dMost, Rate);
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Rate = Rate + tan(deg2rad(90 - slantAngle)) / (1.0 * LineWidth) * Rate;
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if (slantAngle > 89 && slantAngle < 91) {
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printf(" slant OK :)\n");
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break;
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} else if (Retries == 3) {
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printf(" still slanted; giving up\n");
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Rate = SRATE;
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printf(" -> SRATE\n");
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break;
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} else {
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printf(" -> %.2f recalculating\n", Rate);
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Retries ++;
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}
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}
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printf(" gray = %dx%d\n", LineWidth, maxsy);
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// find abscissa at high granularity
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t = 0;
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x = 0;
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xmax=0;
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NextImgSample=0;
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memset(xAcc, 0, sizeof(xAcc[0]) * 700);
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for (s = 0; s < Length; s++) {
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t += 1.0/Rate;
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if (t >= NextImgSample) {
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xAcc[x] += HasSync[s];
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if (xAcc[x] > xAcc[xmax]) xmax = x;
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if (++x >= 700) x = 0;
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NextImgSample += ModeSpec[Mode].LineLen / 700.0;
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}
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}
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// find center of sync pulse
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x0 = -1;
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xmid=-1;
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for (x=0;x<700;x++) {
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if (xAcc[x] >= xAcc[xmax]*0.5 && x0==-1) x0 = x;
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if (x0 != -1 && xAcc[x] < xAcc[xmax]*0.5) {
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xmid = (x + x0) / 2;
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break;
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}
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}
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// skip until the start of the sync pulse
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s = (xmid / 700.0 * ModeSpec[Mode].LineLen - ModeSpec[Mode].SyncLen/2) * Rate;
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// Scottie modes don't start lines with the sync pulse
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if (Mode == S1 || Mode == S2 || Mode == SDX)
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s -= 2 * (ModeSpec[Mode].SeparatorLen + ModeSpec[Mode].PixelLen*ModeSpec[Mode].ImgWidth) * Rate;
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*Skip = s;
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free(HasSync);
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fftw_destroy_plan(Plan);
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fftw_free(in);
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fftw_free(out);
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return (Rate);
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}
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