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• cinedec : report white balance gain coefficients using metadata

  9 novembre 2014, par Peter Ross

  cinedec : report white balance gain coefficients using metadata
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/cinedec.c

• FFMPEG convert Black&White AVI into h264 that works inside a HTML5 Video tag

  7 mai 2014, par Eager to Learn

  I would like to convert an existing black and white AVI into h264 that works inside an Html5 video tag.

  I’m currently using this ffmpeg command :
  Ffmpeg -i 0 -y -c:v libx264 1

  where 0 is the avi file and 1 is the output h264 file.

  This command does not work for me, it does produce the h264 but it does not play anywhere else than inside a VCL player (go figure).

  Anybody out there, please please help !!!

• FFMPEG : Displaying a white screen using ffplay via a custom decoder

  11 décembre 2013, par Zax

  I have created a dummy decoder, Here in its decode function, i would be assigning the output file pointer with a YUV420 data filled with 255 (i.e. a white screen).

  I also have a corresponding probe function for my dummy decoder, where it takes an dummy input file and based on some checking i return AVPROBE_SCORE_MAX. This probe section works perfectly fine and invokes my custom dummy decoder.

  The AVCodec structure of for my dummy decoder is as shown below :

  AVCodec ff_dummyDec_decoder = {
  
      .name           = "dummyDec",
  
      .type           = AVMEDIA_TYPE_VIDEO,
  
      .id             = AV_CODEC_ID_MYDEC,
  
      .priv_data_size = sizeof(MYDECContext),
  
      .pix_fmts       = (const enum AVPixelFormat[]) {AV_PIX_FMT_YUV420P},
  
      .init           = dummyDec_decode_init,
  
      .close          = dummyDec_decode_close,
  
      .decode         = dummyDec_decode_frame,
  
  };

  Where,

  .init -> is a pointer to a function that performs my decoder related initializations
  
  .close -> is a pointer to a function that frees all memory that was allocated during initialization
  
  .decode -> is pointer to a function that decodes a frame.

  The definitions for the above functions is shown below :

  #include 
  
  #include 
  
  #include "avcodec.h"
  
  
  
  unsigned char *yPtr=NULL;
  
  unsigned char *uPtr=NULL;
  
  unsigned char *vPtr=NULL;
  
  
  
  int memFlag=0;//If memFlag is zero then allocate memory for YUV data
  
  
  
  int width=416;//Picture width and height that i want to display in ffplay
  
  int height=240;
  
  
  
  static int dummyDec_decode_frame(AVCodecContext *avctx, void *data,
  
                               int *got_frame_ptr, AVPacket *avpkt)
  
  {
  
      AVFrame *frame=data; //make frame point to the pointer on which output should be mapped
  
      printf("\nDecode function entered\n");
  
      frame->width=width;
  
      frame->height=height;
  
      frame->format=AV_PIX_FMT_YUV420P;
  
  
  
      //initialize frame->linesize[] array
  
      avpicture_fill((AVPicture*)frame, NULL, frame->format,frame->width,frame->height);
  
  
  
      frame->data[0]=yPtr;
  
      frame->data[1]=uPtr;
  
      frame->data[2]=vPtr;
  
  
  
      *got_frame_ptr = 1;
  
  
  
      printf("\nGotFramePtr set to 1\n");
  
  
  
      return width*height+(width/2)*(height/2)+(width/2)*(height/2);//returning the amount of bytes being used
  
  }
  
  
  
  static int dummyDec_decode_init(AVCodecContext *avctx)
  
  {
  
      printf("\nDummy Decoders init entered\n");
  
  
  
      //Allocate memory for YUV data
  
      yPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width*height);
  
      uPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width/2*height/2);
  
      vPtr=(unsigned char*)malloc(sizeof(unsigned char*)*width/2*height/2);
  
  
  
      if(yPtr == NULL || uPtr ==NULL ||vPtr==NULL)
  
          exit(0);
  
  
  
      //set allocated memory with 255 i.e white color
  
     memset(yPtr,255,width*height);
  
     memset(uPtr,255,width/2*height/2);
  
     memset(vPtr,255,width/2*height/2);
  
  }
  
  
  
  static int dummyDec_decode_close(AVCodecContext *avctx)
  
  {
  
      free(yPtr);
  
      free(uPtr);
  
      free(vPtr);
  
  }

  From the dummyDec_decode_frame() function, i'm returning the number of bytes that are being used to display the white colour. Is this right ? Secondly, I have no parser for my decoder, because i'm just mapping a yuv buffer containing white data to AVFrame structure pointer.

  The command that i use for executing is :

  ./ffplay -vcodec dummyDec -i input.bin

  The output is an infinite loop with the following messages :

  dummyDec probe entered
  
  
  
  Dummy Decoders init entered
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  Decode function entered
  
  
  
  GotFramePtr set to 1
  
  
  
  .
  
  
  
  .
  
  
  
  .(the last two messages keep repeating)

  Where is it i'm going wrong ? is it the absence of parser or something else ? I'm unable to proceed because of this. Please provide your valuable answers. Thanks in advance.

  —Regards