text: /*
   * Copyright (c) 2001 Fabrice Bellard
   *
   * 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];
  
      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;
  }
  