FFmpeg: decode_video.c

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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>
   
    #include <
    
     libavcodec/avcodec.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);
  
    static
   
    void
   
    decode
   
   (
   
    AVCodecContext
   
   *
   
    dec_ctx
   
   ,
   
    AVFrame
   
   *
   
    frame
   
   ,
   
    AVPacket
   
   *
   
    pkt
   
   ,
  
    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;
  
    AVCodecParserContext
   
   *parser;
  
    AVCodecContext
   
   *
   
    c
   
   =
   
    NULL
   
   ;
  
   FILE *f;
  
    AVFrame
   
   *
   
    frame
   
   ;
  
    uint8_t
   
   inbuf[
   
    INBUF_SIZE
   
   +
   
    AV_INPUT_BUFFER_PADDING_SIZE
   
   ];
  
    uint8_t
   
   *
   
    data
   
   ;
  
    size_t
   
   data_size;
  
    int
   
   ret;
  
    AVPacket
   
   *
   
    pkt
   
   ;
  
    if
   
   (argc <= 2) {
  
   fprintf(stderr,
   
    "Usage: %s <input file> <output file>\n"
   
   , argv[0]);
  
   exit(0);
  
   filename    = argv[1];
  
   outfilename = argv[2];
  
    avcodec_register_all
   
   ();
  
   pkt =
   
    av_packet_alloc
   
   ();
  
    if
   
   (!pkt)
  
   exit(1);
  
    /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
   
   memset(inbuf +
   
    INBUF_SIZE
   
   , 0,
   
    AV_INPUT_BUFFER_PADDING_SIZE
   
   );
  
    /* find the MPEG-1 video decoder */
   
   codec =
   
    avcodec_find_decoder
   
   (
   
    AV_CODEC_ID_MPEG1VIDEO
   
   );
  
    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);
  
   c =
   
    avcodec_alloc_context3
   
   (codec);
  
    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);
  
   frame =
   
    av_frame_alloc
   
   ();
  
    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);
  
    av_parser_close
   
   (parser);
  
    avcodec_free_context
   
   (&c);
  
    av_frame_free
   
   (&frame);
  
    av_packet_free
   
   (&pkt);
  
    return
   
   0;