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• lavf : introduce AVFMT_TS_NEGATIVE

  3 avril 2013, par Luca Barbato

  lavf : introduce AVFMT_TS_NEGATIVE
  Most formats do not support negative timestamps, shift them to avoid
  
  unexpected behaviour and a number of bad crashes.
  CC:libav-stable@libav.org
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] libavformat/avformat.h
  • [DBH] libavformat/ffmenc.c
  • [DBH] libavformat/framecrcenc.c
  • [DBH] libavformat/md5enc.c
  • [DBH] libavformat/mux.c
  • [DBH] libavformat/oggenc.c
  • [DBH] tests/ref/lavf/asf
  • [DBH] tests/ref/lavf/mkv
  • [DBH] tests/ref/lavf/mpg
  • [DBH] tests/ref/lavf/ts
  • [DBH] tests/ref/seek/lavf-asf
  • [DBH] tests/ref/seek/lavf-mkv
  • [DBH] tests/ref/seek/lavf-mpg
  • [DBH] tests/ref/seek/lavf-ts

• Read/write to stream with JavaCV

  4 juillet 2013, par Zielony

  I'm trying to make use of JavaCV for android. I would like to create a video stream composed of screenshots. I found out that I can write a file using FFmpegFrameRecorder, but I can't write to a stream, array, buffer, or anything else, other than a file.

  Next thing is that I found a piece of code featuring custom FrameRecorder using 'avio_alloc_context' and read/write/seek callbacks. Unfortunately it's only a snippet and it's in C++. 'avio_alloc_context' method on android takes Read_packet, Read_packet and Seek callbacks, so I cannot pass a Write_packet callback. Moreover, right after 'avio_alloc_context' call, I get 'finalize' called on all objects passed to 'avio_alloc_context'.

  final VideoOutputStream videoOutputStream = new VideoOutputStream(stream);
  
  
  
  Read_packet read_packet = new Read_packet() {
  
      @Override
  
      public int call(Pointer arg0, BytePointer arg1, int arg2) {
  
          VideoOutputStream videoStream = (VideoOutputStream) arg0;
  
          try {
  
              videoStream.write(arg1.getStringBytes());
  
          } catch (IOException e) {
  
              e.printStackTrace();
  
          }
  
          return arg2;
  
      }
  
  };
  
  
  
  AVIOContext pb = avio_alloc_context(new MBytePointer(av_malloc(video_outbuf_size)), video_outbuf_size, 1,videoOutputStream, null, read_packet, null);
  
  
  
  oc.pb(pb);

  Using the above code nothing crashes nor reports errors. I just keep getting empty files.

  My question is - does anyone of you guys managed to get it working ? Do you know a correct way to initialize custom reading/writing in FrameRecorder/Grabber in JavaCV ?

• How to save an SDL bitmap to memory and load it back ?

  19 novembre 2012, par Nav

  I have a bunch of RWops functions :

  static int myseekfunc(SDL_RWops *context, int offset, int whence) { SDL_SetError("Can't seek in this kind of RWops"); return(-1); }
  
  static int myreadfunc(SDL_RWops *context, void *ptr, int size, int maxnum) { memset(ptr,0,size*maxnum); return(maxnum); }
  
  static int mywritefunc(SDL_RWops *context, const void *ptr, int size, int num) { return(num); }
  
  static int myclosefunc(SDL_RWops *context) 
  
  { 
  
    if(context->type != 0xdeadbeef) { SDL_SetError("Wrong kind of RWops for myclosefunc()"); return(-1); }
  
    free(context->hidden.unknown.data1);
  
    SDL_FreeRW(context);
  
    return(0);
  
  }
  
  
  
  // Note that this function is NOT static -- we want it directly callable from other source files 
  
  SDL_RWops *MyCustomRWop()
  
  {
  
    SDL_RWops *c=SDL_AllocRW();
  
    if(c==NULL) return(NULL);
  
  
  
    c->seek =myseekfunc;
  
    c->read =myreadfunc;
  
    c->write=mywritefunc;
  
    c->close=myclosefunc;
  
    c->type =0xdeadbeef;
  
    printf("deadbeef=%d\n",c->type);
  
    c->hidden.unknown.data1=malloc(256);//IS THIS CORRECT?
  
    return(c);
  
  }

  with which I'm trying to write a BMP into memory and then extract it back. The below code is from tutorial02.
  Two problems I'm facing are :
  1. Unless I call SDL_DisplayYUVOverlay, the SDL_SaveBMP function outputs a blank BMP file to the hard disk. How can I output a BMP file without having to call SDL_DisplayYUVOverlay ?
  2. Although I'm able to save the BMP to memory with SDL_SaveBMP_RW and free the memory with filestream->close, I'm unable to load the BMP back from memory with SDL_SaveBMP. The application crashes while trying to load it. Is it because of the c->hidden.unknown.data1=malloc(256); code above ? What would be the right way of allocating this memory ?

    AVFormatContext *pFormatCtx = NULL;
  
    int             i, videoStream;
  
    AVCodecContext  *pCodecCtx = NULL;
  
    AVCodec         *pCodec = NULL;
  
    AVFrame         *pFrame = NULL; 
  
    AVPacket        packet;
  
    SDL_Overlay     *bmp = NULL;
  
    SDL_Surface     *screen = NULL;
  
    SDL_Surface     *screen2 = NULL;
  
    SDL_Rect        rect;
  
  ....
  
  ....    
  
  if(frameFinished) 
  
  
  
  {
  
  SDL_LockYUVOverlay(bmp);//-----------lock
  
  
  
  AVPicture pict;
  
  pict.data[0] = bmp->pixels[0];
  
  pict.data[1] = bmp->pixels[2];
  
  pict.data[2] = bmp->pixels[1];
  
  
  
  pict.linesize[0] = bmp->pitches[0];
  
  pict.linesize[1] = bmp->pitches[2];
  
  pict.linesize[2] = bmp->pitches[1];
  
  
  
  // Convert the image into YUV format that SDL uses
  
  sws_scale( sws_ctx, (uint8_t const * const *)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize );
  
  
  
  SDL_UnlockYUVOverlay(bmp);//-----------unlock
  
  
  
  rect.x = 0;
  
  rect.y = 0;
  
  rect.w = pCodecCtx->width;
  
  rect.h = pCodecCtx->height;
  
  SDL_DisplayYUVOverlay(bmp, &rect);
  
  ++i;
  
  
  
  SDL_RWops *filestream = MyCustomRWop();//SDL_AllocRW();
  
  SDL_SaveBMP_RW (screen, filestream, i);
  
  screen2 = SDL_LoadBMP_RW(filestream,1);//LOADING IS THE PROBLEM HERE. DON'T KNOW WHY
  
  filestream->close;
  
  SDL_SaveBMP(screen, filepointer);