Problem mit libav

int count = 0;
  AVPacket packet;
  av_init_packet(&packet);
  AVFrame *pFrame;
  pFrame = avcodec_alloc_frame();
  avcodec_get_frame_defaults(pFrame); // reset frame
  int gotPicture = 0;
  QString type;
  int ret;
  // output frame types for all frames
  while (av_read_frame(m_formatContext, &packet) == 0) {
    if (packet.stream_index != videoStreamIndex) { //only check the frame that belong to the current stream
      av_free_packet(&packet);
      continue;
    }


// HERE avcodec_decode_video2 crashes
    ret = avcodec_decode_video2(codecContext, pFrame, &gotPicture, &packet);


    // never reached :(


    if (ret < 0) {
      ui.textBrowser->append(tr("Error decoding video,..."));
      return;
    }


    // get frame type
    if (gotPicture) {
      count++;
      type = frameTypeToString(pFrame->pict_type, pFrame->key_frame);
      ui.textBrowser->append(tr("Frame %1, type: %2").arg(count).arg(type));
      avcodec_get_frame_defaults(pFrame); // reset frame
    }


    // free&reset stuff
    av_free_packet(&packet);
    gotPicture = 0;
  }