A simple implementation of an encoder for the Robot36 SSTV mode. It uses jpeglib and sndfile and is just the basic encoder, with no frills.

Makefile

#

CFLAGS=-I/u0/markv/include -g
LDFLAGS=-L/u0/markv/lib 
LIBS=-lsndfile -ljpeg -lm

all: robot36

robot36: robot36.o
	$(CC) -o $@ $(LDFLAGS) robot36.o $(LIBS)

robot36.c

#include <stdio.h>
#include <stdlib.h>
#include <complex.h>
#include <math.h>
#include <setjmp.h>
#include <assert.h>

/* 
 * $Id$
 *  ___  ___  ___  ___ _____ ____  __ 
 * | _ \/ _ \| _ )/ _ \_   _|__ / / / 
 * |   / (_) | _ \ (_) || |  |_ \/ _ \
 * |_|_\\___/|___/\___/ |_| |___/\___/
 *                                    
 * An implementation of a Robot 36 SSTV encoder
 * Written by Mark VandeWettering (K6HX)
 */

/* JPEG related headers */
#include <jpeglib.h>
#include <jerror.h>

/* soundfile related headers */
#include <sndfile.h>


#define WIDTH 		320
#define HEIGHT		240
#define HALFWIDTH	(WIDTH/2)
#define HALFHEIGHT	(HEIGHT/2)

typedef float Image[HEIGHT][WIDTH][3] ;
typedef float HalfImage[HALFHEIGHT][HALFWIDTH][3] ;

Image image ;

int
ReadImage(char *fname, Image img) 
{
    FILE *inp ;
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;
    int stride, x, y, c, idx ;
    JSAMPARRAY buffer ;


    if ((inp = fopen(fname, "rb")) == NULL) {
	fprintf(stderr, "can't open %s\n", fname);
	return 0;
    }

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_decompress(&cinfo);
    jpeg_stdio_src(&cinfo, inp);
    (void) jpeg_read_header(&cinfo, TRUE);
    (void) jpeg_start_decompress(&cinfo);

    if (cinfo.image_width != WIDTH || 
	cinfo.image_height != HEIGHT) {
	fprintf(stderr, "image size is %dx%d, should be %dx%d.\n",
		cinfo.image_width, cinfo.image_height, WIDTH, HEIGHT) ;
	return 0 ; 
    }

    /* this would be a programming error if it failed. */
    assert(cinfo.output_components == 3) ;

    stride = cinfo.output_width * cinfo.output_components;
    buffer = (*cinfo.mem->alloc_sarray)
		((j_common_ptr) &cinfo, JPOOL_IMAGE, stride, 1);

    while (cinfo.output_scanline < cinfo.output_height) {
	y = cinfo.output_scanline ;
	(void) jpeg_read_scanlines(&cinfo, buffer, 1);
	/* copy out the data into the image */
        for (x=0, idx=0; x<cinfo.output_width; x++) {
	    for(c=0; c<3; c++, idx++)
		img[y][x][c] = buffer[0][idx]/(float)MAXJSAMPLE ;
	}
    }

    (void) jpeg_finish_decompress(&cinfo);
    jpeg_destroy_decompress(&cinfo);
    fclose(inp);
    return 1 ;
}

#define 	SAMPLERATE	11025

SNDFILE *sf ;
SF_INFO sfinfo ;

complex osc = 0.95 ;

void
blank(float ms)
{
   int nsamp = (int) (SAMPLERATE * ms / 1000.) ;
   int i ;
   float r = 0.0 ;
   for (i=0; i<nsamp; i++)
	sf_write_float(sf, &r, 1) ;
}

void
pulse(float freq, float ms)
{
   /* convert ms to samples */
   int nsamp = (int) (SAMPLERATE * ms / 1000.) ;
   int i ;
   float r ;
   complex m = cexp(I*2.0*M_PI*freq / SAMPLERATE) ;

   for (i=0; i<nsamp; i++) {
	osc *= m ;
	r = creal(osc) ;
        sf_write_float(sf, &r, 1) ;
   }
}

void
Vis(int code)
{
    int i ;

    pulse(1900, 300.0) ;
    pulse(1200, 10.0) ;
    pulse(1900, 300.0) ;
    pulse(1200, 30.0) ;		/* start bit */
    for (i=0; i<8; i++) {
	if (code & 1)
	    pulse(1100, 30.0) ;
	else
	    pulse(1300, 30.0) ;
	code = code >> 1 ;
    }
    pulse(1200, 30.0) ;		/* stop bit */
}

void
ScanlinePair(Image img, HalfImage halfimg, int y)
{
    int i, j ;
    int ysamp = 88 * SAMPLERATE / 1000 ;
    int samp = 44 * SAMPLERATE / 1000 ;

    pulse(1200, 9.0) ;		/* sync pulse */
    pulse(1500, 3.0) ;		/* sync porch */

    /* pulse(1600, 88.0) ; */
    for (i=0; i<ysamp; i++) {
	int idx = i * WIDTH / ysamp ; 
	float f = 0.0625 + 0.9375 * image[y][idx][0] ;
 	float freq = 1500.0 + (2300.0-1500.0) * f ;
	complex m = cexp(I*2.0*M_PI*freq/SAMPLERATE) ;
	osc *= m ;
	float r = creal(osc) ;
        sf_write_float(sf, &r, 1) ;
    }

    pulse(1500, 4.5) ;		/* even separator pulse */
    pulse(1900, 1.5) ;		/* porch */    

    /* pulse(1900, 44.0) ; */
    for (i=0; i<samp; i++) {
	int idx = i * HALFWIDTH / samp ; 
	float f = 0.0625 + 0.9375 * halfimg[y/2][idx][1] ;
 	float freq = 1500.0 + (2300.0-1500.0) * f ;
	complex m = cexp(I*2.0*M_PI*freq/SAMPLERATE) ;
	osc *= m ;
	float r = creal(osc) ;
        sf_write_float(sf, &r, 1) ;
    }

    pulse(1200, 9.0) ;		/* sync pulse */
    pulse(1500, 3.0) ;		/* sync porch */
 
    /* pulse(1600, 88.0) ; */
    for (i=0; i<ysamp; i++) {
	int idx = i * WIDTH / ysamp ; 
	float f = 0.0625 + 0.9375 * image[y+1][idx][0] ;
 	float freq = 1500.0 + (2300.0-1500.0) * f ;
	complex m = cexp(I*2.0*M_PI*freq/SAMPLERATE) ;
	osc *= m ;
	float r = creal(osc) ;
        sf_write_float(sf, &r, 1) ;
    }


    pulse(2300, 4.5) ;		/* odd separator pulse */
    pulse(1900, 1.5) ;		/* porch */    
    /* pulse(1900, 44.0) ; */

    for (i=0; i<samp; i++) {
	int idx = i * HALFWIDTH / samp ; 
	float f = 0.0625 + 0.9375 * halfimg[y/2][idx][2] ;
 	float freq = 1500.0 + (2300.0-1500.0) * f ;
	complex m = cexp(I*2.0*M_PI*freq/SAMPLERATE) ;
	osc *= m ;
	float r = creal(osc) ;
        sf_write_float(sf, &r, 1) ;
    }


}

int
main(int argc, char *argv[])
{
    char *fname = "wally.jpg" ;
    int y, i, j, c ;
    HalfImage halfimage ;

    if (ReadImage(fname, image))
	fprintf(stderr, "%s read successfully.\n", fname) ;

    /* downsample */
    for (j=0; j<HALFHEIGHT; j++) {
	for (i=0; i<HALFWIDTH; i++) {
	    for (c=0; c<3; c++)
		halfimage[j][i][c] = 
		    (image[2*j][2*i][c] +
		    image[2*j+1][2*i][c] +
		    image[2*j][2*i+1][c] +
		    image[2*j+1][2*i+1][c]) / 4.0 ;
	}
    }

    /* now, color space convert */
    for (j=0; j<HEIGHT; j++) {
	for (i=0; i<WIDTH; i++) {
	    image[j][i][0] = 0.30 * image[j][i][0] +
			     0.59 * image[j][i][1] +
			     0.11 * image[j][i][2] ;
	}
    }
    /* and the half image */
    for (j=0; j<HALFHEIGHT; j++) {
	for (i=0; i<HALFWIDTH; i++) {
	    float y = 0.30 * halfimage[j][i][0] +
		      0.59 * halfimage[j][i][1] +
		      0.11 * halfimage[j][i][2] ;
	    halfimage[j][i][1] = (halfimage[j][i][0] - y + 1.0) / 2.0 ; 
	    halfimage[j][i][2] = (halfimage[j][i][2] - y + 1.0) / 2.0 ;
	    halfimage[j][i][0] = y ;
	}
     }

    sfinfo.channels = 1 ;
    sfinfo.samplerate = SAMPLERATE ;
    sfinfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16 ;

    sf = sf_open("wally.wav", SFM_WRITE, &sfinfo) ;

    /* generate the "vis" code. */
    blank(500.0) ;
    Vis(128+8) ;

    for (y=0; y<HEIGHT; y += 2)
	ScanlinePair(image, halfimage, y) ;

    blank(500.0) ;

    sf_close(sf) ;

    return 0 ;
}


/*
 * $Log$
 */

I do not know how can I get sndfile and jpeglib. Please help.