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* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
* @file
* video decoding with libavcodec API example
* @example decode_video.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INBUF_SIZE 4096
static void pgm_save ( unsigned char * buf , int wrap , int xsize, int ysize,
char *filename)
FILE *f;
int i;
f = fopen(filename, "w" );
fprintf(f, "P5\n%d %d\n%d\n" , xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
fclose(f);
const char *filename)
char buf [1024];
int ret;
ret = avcodec_send_packet (dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n" );
exit(1);
while (ret >= 0) {
ret = avcodec_receive_frame (dec_ctx, frame);
if (ret == AVERROR (EAGAIN) || ret == AVERROR_EOF )
return ;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n" );
exit(1);
printf( "saving frame %3d\n" , dec_ctx-> frame_number );
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
snprintf (buf, sizeof (buf), "%s-%d" , filename, dec_ctx-> frame_number );
pgm_save (frame-> data [0], frame-> linesize [0],
frame-> width , frame-> height , buf);
int main ( int argc, char **argv)
const char *filename, *outfilename;
const AVCodec *codec;
FILE *f;
size_t data_size;
int ret;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file> <output file>\n" , argv[0]);
exit(0);
filename = argv[1];
outfilename = argv[2];
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
/* find the MPEG-1 video decoder */
if (!codec) {
fprintf(stderr, "Codec not found\n" );
exit(1);
parser = av_parser_init (codec-> id );
if (!parser) {
fprintf(stderr, "parser not found\n" );
exit(1);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n" );
exit(1);
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if ( avcodec_open2 (c, codec, NULL ) < 0) {
fprintf(stderr, "Could not open codec\n" );
exit(1);
f = fopen(filename, "rb" );
if (!f) {
fprintf(stderr, "Could not open %s\n" , filename);
exit(1);
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n" );
exit(1);
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE , f);
if (!data_size)
break ;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret = av_parser_parse2 (parser, c, &pkt-> data , &pkt-> size ,
data, data_size, AV_NOPTS_VALUE , AV_NOPTS_VALUE , 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n" );
exit(1);
data += ret;
data_size -= ret;
if (pkt-> size )
decode (c, frame, pkt, outfilename);
/* flush the decoder */
decode (c, frame, NULL , outfilename);
fclose(f);
return 0;