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• JNI crash when I split code in two functions

  13 septembre 2013, par Lescott

  I have a properly working native C function which I call from my java code. But when I split this code in two functions and sequentially call them both I got fatal error.

  //global variables
  
  AVFormatContext *pFormatCtx;
  
  AVFrame         *pFrame;
  
  AVFrame         *pFrameRGB;
  
  AVCodecContext  *pCodecCtx;
  
  AVCodec         *pCodec;
  
  uint8_t         *buffer;
  
  int             videoStream;
  
  struct SwsContext      *sws_ctx = NULL;
  
  int outWidth, outHeight;

  Working unsplitted function

  JNIEXPORT void JNICALL Java_foo(JNIEnv * env, jclass class) {
  
      av_register_all();
  
      const char* videoPath = "11.mp4";
  
  
  
      int             numBytes;
  
      AVDictionary    *optionsDict = NULL;
  
  
  
      pFrame = NULL; 
  
      pFrameRGB = NULL;
  
      buffer = NULL;
  
      pCodec = NULL;
  
      pFormatCtx = NULL;
  
  
  
      // Open video file
  
      if(avformat_open_input(&pFormatCtx, videoPath, NULL, NULL)!=0)
  
              exit(1); // Couldn't open file
  
  
  
  
  
      // Retrieve stream information
  
      if(avformat_find_stream_info(pFormatCtx, NULL)<0)
  
              exit(1); // Couldn't find stream information
  
  
  
       av_dump_format(pFormatCtx, 0,videoPath, 0);
  
  
  
  
  
      // Find the first video stream
  
      videoStream=-1;
  
      int i;
  
      for(i=0; inb_streams; i++) {
  
              if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
  
                      videoStream=i;
  
                      break;
  
              }
  
      }
  
  
  
      if(videoStream==-1)
  
              exit(1); // Didn't find a video stream
  
  
  
      // Get a pointer to the codec context for the video stream
  
      pCodecCtx=pFormatCtx->streams[videoStream]->codec;
  
  
  
  
  
      // Find the decoder for the video stream
  
      pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
      if(pCodec==NULL) {
  
              fprintf(stderr, "Unsupported codec!\n");
  
              exit(1); // Codec not found
  
      }
  
  
  
      // Open codec
  
      if(avcodec_open2(pCodecCtx, pCodec, &optionsDict)<0)
  
              exit(1); // Could not open codec
  
  
  
      // Allocate video frame
  
      pFrame=avcodec_alloc_frame();
  
  
  
      // Allocate an AVFrame structure
  
      pFrameRGB=avcodec_alloc_frame();
  
      if(pFrameRGB==NULL)
  
              exit(1);
  
  
  
      outWidth = 128;
  
      outHeight = 128;
  
  
  
      // Determine required buffer size and allocate buffer
  
      numBytes=avpicture_get_size(PIX_FMT_RGB24, outWidth, outHeight);
  
      buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
  
  
  
      sws_ctx = sws_getContext(
  
                              pCodecCtx->width,
  
                              pCodecCtx->height,
  
                              pCodecCtx->pix_fmt,
  
                              outWidth,
  
                              outHeight,
  
                              PIX_FMT_RGB24,
  
                              SWS_BILINEAR,
  
                              NULL,
  
                              NULL,
  
                              NULL
  
                      );
  
  
  
      // Assign appropriate parts of buffer to image planes in pFrameRGB
  
      // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
  
      // of AVPicture
  
      avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24, outWidth, outHeight);
  
  }

  Failing splitted functions

  JNIEXPORT void JNICALL Java_foo1(JNIEnv * env, jclass class) {
  
      av_register_all();
  
  }
  
  
  
  JNIEXPORT void JNICALL Java_foo2(JNIEnv * env, jclass class) {
  
      //all lines of code from Java_foo exept the first
  
  }

  Java code

  System.loadLibrary("mylib");
  
  Mylib.foo1();
  
  Mylib.foo2(); //fatal error
  
  
  
  
  
  #
  
  # A fatal error has been detected by the Java Runtime Environment:
  
  #
  
  #  SIGSEGV (0xb) at pc=0x00007faab5012dc0, pid=15571, tid=140371352766208

  Any ideas ?

• How is video decoding corruption be debugged ?

  17 septembre 2013, par TopGunCoder

  I just started working for a new company and my new role demands that I help debug the video corruption that they are receiving through decoding frames. As much as I intend on digging down deep into the code and looking into the specifics of my problem, it made me think about video debugging in general.

  Since handling videos is very new to me, the whole process seems pretty complex and it seems there are a lot of places for corruption to present itself. The way I see it there is at least three places where corruption could pop up (barring memory corruption from the machine) :

  • Transporting the data before it is decoded
  • decoding implementation that perpetuates corruption once it is encountered, or is all together incorrect (Which seems to be my problem)
  • Transportation to the monitor(which seems unlikely but possible)

  So what i'm really curious about is if/how people debug their video streams to determine the location of any potential corruption they are encountering. I'm sure there is no sure fire method but I am curious to see what problems are even possible and how they can be identified and triaged.

  P.S. - I'm not sure of the differences between different decoding methods but, if this question seems too vague maybe it helps to mention I am using ffmpeg and avcodec_decode_video2 for the decoding.

• playing MPEG-dash streaming with FFMPEG [on hold]

  9 mars 2019, par Thanh Nguyen

  I’m having a problem when playing MPEG-dash streaming with ffmpeg. I know there are a lot of tools can play MPEG-dash like OSMO4, DASH.js.. However, I am wondering if I can play MPEG-dash with FFMPEG ?
  And one more question, How can I determine startup time when playing MPEG-dash streaming ? It means, the duration time when I request a MPD file from a server until I get the first picture of video display on a screen ?
  Thanks !