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/* avcodec API use example.
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* Note that this library only handles codecs (mpeg, mpeg4, etc...),
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* not file formats (avi, vob, etc...). See library 'libav' for the
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#define INBUF_SIZE 4096
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* Audio encoding example
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void audio_encode_example(const char *filename)
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AVCodecContext codec_context, *c = &codec_context;
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int frame_size, i, j, out_size, outbuf_size;
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printf("Audio encoding\n");
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/* find the MP2 encoder */
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codec = avcodec_find_encoder(CODEC_ID_MP2);
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fprintf(stderr, "codec not found\n");
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/* put default values */
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memset(c, 0, sizeof(*c));
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/* put sample parameters */
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c->sample_rate = 44100;
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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/* the codec gives us the frame size, in samples */
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frame_size = c->frame_size;
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samples = malloc(frame_size * 2 * c->channels);
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outbuf = malloc(outbuf_size);
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f = fopen(filename, "w");
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fprintf(stderr, "could not open %s\n", filename);
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/* encode a single tone sound */
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tincr = 2 * M_PI * 440.0 / c->sample_rate;
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for(j=0;j<frame_size;j++) {
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samples[2*j] = (int)(sin(t) * 10000);
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samples[2*j+1] = samples[2*j];
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/* encode the samples */
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out_size = avcodec_encode_audio(c, outbuf, outbuf_size, samples);
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fwrite(outbuf, 1, out_size, f);
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void audio_decode_example(const char *outfilename, const char *filename)
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AVCodecContext codec_context, *c = &codec_context;
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int out_size, size, len;
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UINT8 inbuf[INBUF_SIZE], *inbuf_ptr;
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printf("Audio decoding\n");
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/* find the mpeg audio decoder */
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codec = avcodec_find_decoder(CODEC_ID_MP2);
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fprintf(stderr, "codec not found\n");
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/* put default values */
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memset(c, 0, sizeof(*c));
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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outbuf = malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE);
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f = fopen(filename, "r");
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fprintf(stderr, "could not open %s\n", filename);
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outfile = fopen(outfilename, "w");
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fprintf(stderr, "could not open %s\n", outfilename);
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/* decode until eof */
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size = fread(inbuf, 1, INBUF_SIZE, f);
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len = avcodec_decode_audio(c, (short *)outbuf, &out_size,
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fprintf(stderr, "Error while decoding\n");
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/* if a frame has been decoded, output it */
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fwrite(outbuf, 1, out_size, outfile);
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* Video encoding example
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void video_encode_example(const char *filename)
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AVCodecContext codec_context, *c = &codec_context;
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int i, out_size, size, x, y, outbuf_size;
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UINT8 *outbuf, *picture_buf;
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printf("Video encoding\n");
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/* find the mpeg1 video encoder */
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codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
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fprintf(stderr, "codec not found\n");
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/* put default values */
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memset(c, 0, sizeof(*c));
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/* put sample parameters */
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c->bit_rate = 400000;
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/* resolution must be a multiple of two */
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/* frames per second */
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c->frame_rate = 25 * FRAME_RATE_BASE;
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c->gop_size = 10; /* emit one intra frame every ten frames */
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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/* the codec gives us the frame size, in samples */
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f = fopen(filename, "w");
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fprintf(stderr, "could not open %s\n", filename);
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/* alloc image and output buffer */
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outbuf_size = 100000;
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outbuf = malloc(outbuf_size);
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size = c->width * c->height;
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picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
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picture.data[0] = picture_buf;
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picture.data[1] = picture.data[0] + size;
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picture.data[2] = picture.data[1] + size / 4;
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picture.linesize[0] = c->width;
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picture.linesize[1] = c->width / 2;
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picture.linesize[2] = c->width / 2;
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/* encode 1 second of video */
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printf("encoding frame %3d\r", i);
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/* prepare a dummy image */
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for(y=0;y<c->height;y++) {
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for(x=0;x<c->width;x++) {
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picture.data[0][y * picture.linesize[0] + x] = x + y + i * 3;
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for(y=0;y<c->height/2;y++) {
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for(x=0;x<c->width/2;x++) {
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picture.data[1][y * picture.linesize[1] + x] = 128 + y + i * 2;
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picture.data[2][y * picture.linesize[2] + x] = 64 + x + i * 5;
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/* encode the image */
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out_size = avcodec_encode_video(c, outbuf, outbuf_size, &picture);
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fwrite(outbuf, 1, out_size, f);
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/* add sequence end code to have a real mpeg file */
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fwrite(outbuf, 1, 4, f);
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* Video decoding example
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void pgm_save(unsigned char *buf,int wrap, int xsize,int ysize,char *filename)
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f=fopen(filename,"w");
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fprintf(f,"P5\n%d %d\n%d\n",xsize,ysize,255);
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fwrite(buf + i * wrap,1,xsize,f);
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void video_decode_example(const char *outfilename, const char *filename)
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AVCodecContext codec_context, *c = &codec_context;
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int frame, size, got_picture, len;
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UINT8 inbuf[INBUF_SIZE], *inbuf_ptr;
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printf("Video decoding\n");
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/* find the mpeg1 video decoder */
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codec = avcodec_find_decoder(CODEC_ID_MPEG1VIDEO);
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fprintf(stderr, "codec not found\n");
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/* put default values */
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memset(c, 0, sizeof(*c));
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/* for some codecs, such as msmpeg4 and mpeg4, width and height
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MUST be initialized there because these info are not available
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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/* the codec gives us the frame size, in samples */
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f = fopen(filename, "r");
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fprintf(stderr, "could not open %s\n", filename);
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size = fread(inbuf, 1, INBUF_SIZE, f);
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/* NOTE1: some codecs are stream based (mpegvideo, mpegaudio)
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and this is the only method to use them because you cannot
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know the compressed data size before analysing it.
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BUT some other codecs (msmpeg4, mpeg4) are inherently frame
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based, so you must call them with all the data for one
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frame exactly. You must also initialize 'width' and
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'height' before initializing them. */
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/* NOTE2: some codecs allow the raw parameters (frame size,
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sample rate) to be changed at any frame. We handle this, so
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you should also take care of it */
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/* here, we use a stream based decoder (mpeg1video), so we
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feed decoder and see if it could decode a frame */
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len = avcodec_decode_video(c, &picture, &got_picture,
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fprintf(stderr, "Error while decoding frame %d\n", frame);
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printf("saving frame %3d\r", frame);
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/* the picture is allocated by the decoder. no need to
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snprintf(buf, sizeof(buf), outfilename, frame);
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pgm_save(picture.data[0], picture.linesize[0],
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c->width, c->height, buf);
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/* some codecs, such as MPEG, transmit the I and P frame with a
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latency of one frame. You must do the following to have a
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chance to get the last frame of the video */
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len = avcodec_decode_video(c, &picture, &got_picture,
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printf("saving frame %3d\r", frame);
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/* the picture is allocated by the decoder. no need to
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snprintf(buf, sizeof(buf), outfilename, frame);
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pgm_save(picture.data[0], picture.linesize[0],
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c->width, c->height, buf);
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int main(int argc, char **argv)
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const char *filename;
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/* must be called before using avcodec lib */
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/* register all the codecs (you can also register only the codec
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you wish to have smaller code */
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avcodec_register_all();
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audio_encode_example("/tmp/test.mp2");
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audio_decode_example("/tmp/test.sw", "/tmp/test.mp2");
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video_encode_example("/tmp/test.mpg");
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filename = "/tmp/test.mpg";
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// audio_decode_example("/tmp/test.sw", filename);
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video_decode_example("/tmp/test%d.pgm", filename);
added
removed
ffmpeg/libavcodec/apiexample.c
