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• Revision c29c613400 : Merge "vp8enc : Prevent out of bounds memory access."

  28 janvier 2015, par Alex Converse

  Merge "vp8enc : Prevent out of bounds memory access."

• Revision c0856b98cc : Merge "Fixing out of bounds access in frame_refs[] array."

  30 janvier 2014, par Yaowu Xu

  Merge "Fixing out of bounds access in frame_refs[] array."

• Access Violation at avcodec_encode_video2()

  23 mars 2016, par bot1131357

  I am trying to understand the FFmpeg API by following online examples available but it seems that the FFmpeg API has changed over time, making most of the examples obsolete ; I hope some of you can help me make more sense of the FFmpeg API examples.

  I am currently trying to understand the encoding-example from FFmpeg, but I am getting an Access Violation error at this line :

  out_size = avcodec_encode_video2(codecCtx, &avpkt, picture, &got_packet);

  where I get "Unhandled exception at 0x77c29e42 in test01_encode.exe : 0xC0000005 : Access violation reading location 0xccccccc8." from Visual Studio.

  I understand that avcodec_encode_video() is deprecated in favour of avcodec_encode_video2(), which uses AVPacket. I’ve allocated a buffer to data member of AVPacket and set its size, but still the same. What did I miss ?

  The library that I’m using is ffmpeg-20160219-git-98a0053-win32-dev. I would really really appreciate if you could help me out of this confusion.

  (Side : What does it mean by "get delayed frames" and why are we encoding by specifying AVFrame* parameter as NULL ?)

  /*
  
   * Video encoding example
  
   */
  
  char filename[] = "test.mpg";
  
  int main(int argc, char** argv)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *codecCtx= NULL;
  
      int i, out_size, size, x, y, outbuf_size;
  
      FILE *f;
  
      AVFrame *picture;
  
      uint8_t *outbuf, *picture_buf;
  
  
  
      printf("Video encoding\n");
  
  
  
      // Register all formats and codecs
  
      av_register_all();
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(AV_CODEC_ID_MPEG1VIDEO);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
      }
  
  
  
      codecCtx= avcodec_alloc_context3(codec);
  
      picture= av_frame_alloc();
  
  
  
      /* put sample parameters */
  
      codecCtx->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      codecCtx->width = 352;
  
      codecCtx->height = 288;
  
      /* frames per second */
  
      //codecCtx->time_base= (AVRational){1,25};
  
      codecCtx->time_base.num = 1;
  
      codecCtx->time_base.den = 25;
  
  
  
      codecCtx->gop_size = 10; /* emit one intra frame every ten frames */
  
      codecCtx->max_b_frames=1;
  
      codecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      /* open it */
  
      if (avcodec_open2(codecCtx, codec, NULL) < 0) {
  
          fprintf(stderr, "could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      fopen_s(&f,filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      /* alloc image and output buffer */
  
      outbuf_size = 100000;
  
      outbuf = (uint8_t*) malloc(outbuf_size);
  
      size = codecCtx->width * codecCtx->height;
  
      picture_buf = (uint8_t*) malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
      picture->data[0] = picture_buf;
  
      picture->data[1] = picture->data[0] + size;
  
      picture->data[2] = picture->data[1] + size / 4;
  
      picture->linesize[0] = codecCtx->width;
  
      picture->linesize[1] = codecCtx->width / 2;
  
      picture->linesize[2] = codecCtx->width / 2;
  
  
  
      picture->width = codecCtx->width;
  
      picture->height = codecCtx->height;
  
      picture->format = codecCtx->pix_fmt;
  
  
  
      AVPacket avpkt;
  
      int got_packet;
  
  
  
      avpkt.size=av_image_get_buffer_size(codecCtx->pix_fmt, codecCtx->width,
  
                      codecCtx->height,1);    
  
      avpkt.data = (uint8_t *)av_malloc(avpkt.size*sizeof(uint8_t));
  
  
  
      /* encode 1 second of video */
  
      for(i=0;i<25;i++) {
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* Y */
  
          for(y=0;yheight;y++) {
  
              for(x=0;xwidth;x++) {
  
                  picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for(y=0;yheight/2;y++) {
  
              for(x=0;xwidth/2;x++) {
  
                  picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
                  picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
              }
  
          }
  
  
  
          /* encode the image */
  
          //out_size = avcodec_encode_video(codecCtx, outbuf, outbuf_size, picture);
  
          // <access violation="violation"> 
  
          out_size = avcodec_encode_video2(codecCtx, &amp;avpkt, picture, &amp;got_packet); 
  
          printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
          //fwrite(outbuf, 1, out_size, f);
  
          fwrite(avpkt.data, 1, avpkt.size, f);
  
      }
  
  
  
      /* get the delayed frames */
  
      for(; out_size; i++) {
  
          fflush(stdout);
  
  
  
          //out_size = avcodec_encode_video(codecCtx, outbuf, outbuf_size, NULL);
  
          out_size = avcodec_encode_video2(codecCtx, &amp;avpkt, NULL, &amp;got_packet); 
  
          printf("write frame %3d (size=%5d)\n", i, out_size);
  
          //fwrite(outbuf, 1, out_size, f);
  
          fwrite(avpkt.data, 1, avpkt.size, f);
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      outbuf[0] = 0x00;
  
      outbuf[1] = 0x00;
  
      outbuf[2] = 0x01;
  
      outbuf[3] = 0xb7;
  
      fwrite(outbuf, 1, 4, f);
  
      fclose(f);
  
      free(picture_buf);
  
      free(outbuf);
  
  
  
      avcodec_close(codecCtx);
  
      av_free(codecCtx);
  
      av_free(picture);
  
      printf("\n");
  
  }
  
  </access>