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• 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);

• ReSample RTP Audio data over Socket as PCM data using FFMPEG

  5 février 2020, par GJ.

  I want to receive a RTP Stream and send the raw data received in it over TCP / UDP socket. For this i am trying following commands.

  1. I am sending the RTP stream using following command.

     ffmpeg -re -i hello.wav -ar 8000 -f mulaw -f rtp rtp ://127.0.0.1:1234

  2. Receiver to re transmit the stream over TCP / UDP socket.

     ffmpeg -i rtp ://127.0.0.1:1234 -f mulaw tcp ://127.0.0.1:5555 -hide_banner

  3. A Player to play this Socket stream to verify.

     ffplay tcp ://127.0.0.1:5555 ?listen

  My second command shows that its receiving data and transmitting the data to tcp over 5555 port.

  Input #0, rtp, from 'rtp://127.0.0.1:1234':
  
    Duration: N/A, start: 0.000000, bitrate: 64 kb/s
  
      Stream #0:0: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (pcm_mulaw (native) -> pcm_mulaw (native))
  
  Press [q] to stop, [?] for help
  
  Output #0, mulaw, to 'tcp://127.0.0.1:5555':
  
    Metadata:
  
      encoder         : Lavf58.29.100
  
      Stream #0:0: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
  
      Metadata:
  
        encoder         : Lavc58.54.100 pcm_mulaw

  But the third command does not receive anything, even i tried dumping the response into a file using FFMPEG in command three but same results.

  What am i doing wrong, Please suggest the correct commands using FFMPEG.

• How to union RAW video data stream with RAW data audio stream through ffmpeg .net

  17 septembre 2022, par zabitstack

  I'm trying to union a raw video data stream with raw audio data stream but without success ! I capture video from webcam and audio from microphone in .net Accord Framework application.

  


  I want use ffmpeg core .net library to transform raw video data into a avi file, then same thing transform raw audio data into mp3 format file. Next merge mp3 with avi in single avi video+audio file.

  


  If you want, I can post source code how I capture data.