[FFmpeg-user] avcodec_decode_video2 question

[Bob Self]

I am trying to get the following program to work to simply get video frames
from an avi file. I will run through this outer loop for about 7000 times,
and
then crashes with an unhandled exception. I'm trying to get individual video
frames so I can display them with opengl. I have a VFW version working that
does that, but would like to switch to ffmpeg.

Is this the correct way to get frames from a video file?

thanks,
Bob


void test_ffmpeg(void)  {
   AVFormatContext *ic;
   char fname[256];
   int err;
   AVCodec *codec=NULL;
   AVCodecContext *codec_context = NULL;
   FILE *stream=NULL;
   AVFrame *picture=NULL;
   int frame, got_picture, len;
   uint8_t inbuf[INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
   char buf[1024];
   AVPacket packet;

   strcpy(fname, "test.avi");


   avcodec_init();
   avcodec_register_all();
   av_init_packet(&packet);

   memset(inbuf + INBUF_SIZE, 0, FF_INPUT_BUFFER_PADDING_SIZE);

   codec = avcodec_find_decoder(CODEC_ID_MPEG4);

   if (!codec) {
      goto finis;
   }

   codec_context = avcodec_alloc_context();
   picture = avcodec_alloc_frame();

   codec_context->debug = FF_DEBUG_PICT_INFO;

   if(codec->capabilities&CODEC_CAP_TRUNCATED)  {
      codec_context->flags|= CODEC_FLAG_TRUNCATED;        // we do not send
complete frames
   }


   if (avcodec_open(codec_context, codec) < 0) {
      bp = 3;
      goto finis;
   }


   stream = fopen(fname, "rb");
   if (!stream) {
      goto finis;
   }

   frame = 0;

   while(1)  {
      packet.size = fread(inbuf, 1, INBUF_SIZE, stream);         // 4096
      if (packet.size == 0)  {
         break;
      }

      packet.data = inbuf;


      while (packet.size > 0) {
         len = avcodec_decode_video2(codec_context, picture, &got_picture,
len ? &packet : NULL);

         if (len < 0) {
                // do what here?
         }

         if (got_picture) {
            frame++;
         }
         else  {
            if (len<0)  {
               break;
            }
         }

         packet.size -= len;
         packet.data += len;
      }            // while (avpkt.size > 0) {
   }               // while(1)  {

   packet.data = NULL;
   packet.size = 0;
   len = avcodec_decode_video2(codec_context, picture, &got_picture,
&packet);

   if (got_picture) {
      frame++;
   }

finis:
   FCLOSE(stream);
   if (codec_context)  {
      avcodec_close(codec_context);
      av_free(codec_context);
      codec_context = NULL;
   }
   if (picture)  {
      av_free(picture);
      picture = NULL;
   }

   return;
}                        // test_ffmpeg()