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• Translating ffmpeg command line to C++ codec settings

  6 mars 2014, par pacificator

  I've been doing some work in ffmpeg for a while in C++.
  Most of the help regarding encoder settings is explained as command line options.
  For example (taken from the ffmpeg site) :

  -mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2’ 

  but beware the ’-g 100’ might cause problems with some decoders. Things to try :

   ’-bf 2’, ’-flags qprd’, ’-flags mv0’, ’- flags skiprd.

  This is not really usefull when you want to set these options in C.
  For example I managed to find int trellis ; in the AVCodecContext struct so that is one solved, but what about the others ?

  Is there a way to determine what command line parameters correspond to what AVCodecContext members ?
  I tried setting them like this :

  AVCodecContext* c;
  
  av_opt_set_int(c->priv_data, "cmp", 2, 0);

  But this returns an error code that the option does not exist.
  I've also tried :

    av_opt_set(c->priv_data, "cmp", "2", 0);

  I still get the error that the option does not exist.

  So, is there a way to determine what AVCodecContext members I should set that are equivalent to the ffmpeg command line parameters above ?

• Recommendataions for robust and invisible video watermarking software / library [on hold]

  1er mars 2014, par id128

  I am doing a research project in search of a robust and invisible video watermarking software / library (preferably in C++). It needs to meet the following requirements :

  • Robust - that is the watermark needs to survive common transformations such as re-encoding, A/D / D/A conversion, luminance/color change, shift, and crop (both in size and length)'

  • Invisible - to the human eye

  The watermark does not need to carry too much data - maybe a 64-bit UUID - and can be temporal or spatial. But I will need the ability to determine the existence (or not) of the watermark with only a few seconds of the video

  Some research I have done so far :

  • JAWS research paper (http://pdf.aminer.org/000/316/002/the_viva_project_digital_watermarking_for_broadcast_monitoring.pdf) but cannot find any implementations on the web and the authors are not responding to emails. Plus, that research is over 10 years old and I am hoping for something more modern.

  • OpenPuff - does not satisfy the robustness requirement in that the resulting video does not survive transformations.

  • ffmpeg software - I have figured out how to overlay a visible watermark, but that does not satisfy the invisibility requirement.

  Any ideas / suggestions / pointers will be awesome. Thanks.

• ffmpeg : RGB to YUV conversion loses color and scale

  27 avril 2015, par learner

  I am trying to convert RGB frames to YUV420P format in ffmpeg/libav. Following is the code for conversion and also the images before and after conversion. The converted image loses all color information and also the scale changes significantly. Does anybody have idea how to handle this ? I am completely new to ffmpeg/libav !

  // Did we get a video frame?
  
     if(frameFinished)
  
     {
  
         i++;
  
         sws_scale(img_convert_ctx, (const uint8_t * const *)pFrame->data,
  
                   pFrame->linesize, 0, pCodecCtx->height,
  
                   pFrameRGB->data, pFrameRGB->linesize);                   
  
  
  
         //==============================================================
  
         AVFrame *pFrameYUV = avcodec_alloc_frame();
  
         // Determine required buffer size and allocate buffer
  
         int numBytes2 = avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,                                 
  
                                            pCodecCtx->height);
  
         uint8_t *buffer = (uint8_t *)av_malloc(numBytes2*sizeof(uint8_t));
  
  
  
         avpicture_fill((AVPicture *)pFrameYUV, buffer, PIX_FMT_RGB24,
  
                         pCodecCtx->width, pCodecCtx->height);
  
  
  
  
  
         rgb_to_yuv_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,  
  
                                         PIX_FMT_RGB24,
  
                                         pCodecCtx->width,pCodecCtx->height, 
  
                                         PIX_FMT_RGB24,
  
                                         SWS_BICUBIC, NULL,NULL,NULL);
  
  
  
         sws_scale(rgb_to_yuv_ctx, pFrameRGB->data, pFrameRGB->linesize, 0, 
  
                   pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
  
  
  
         sws_freeContext(rgb_to_yuv_ctx);
  
  
  
         SaveFrame(pFrameYUV, pCodecCtx->width, pCodecCtx->height, i);
  
  
  
         av_free(buffer);
  
         av_free(pFrameYUV);
  
     }