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• ffmpeg alpha and transition leaving a ghosting effect

  18 octobre 2018, par Amin Baig

  I have the following ffmpeg command :

  //video from image and text insertion in one step
  
  ffmpeg -framerate 30 -loop 1 -t 5 -i 1.jpg -i 3D_Transition_02.mp4 -filter_complex "[0]format=rgba,scale=1280:720,split[img][a]; [1]format=rgb24,negate,scale=1280:720[tr];[a][tr]overlay=format=gbrp[al];[img][al]alphamerge,setsar=1,format=yuva444p,
  
  drawtext=enable='gte(t,.5)':box=1:boxcolor=black@.2:boxborderw=10:fontfile=fonts/Roboto-Black.ttf:fontcolor=white:fontsize=56:shadowcolor=Black:shadowx=1:shadowy=1
  
  :text='Some text here':y=h-th-10:x=10" -an -c:v libvpx -crf 10 -b:v 0 -quality realtime -auto-alt-ref 0 a1.mkv

  Using this command I create a v5 seconds video from a single image, there is a transition effect which is given to the image and then a text is rendered on it using drawtext.
  I create four videos using the above command only changing text and image, then I used the following command to conbine the four generated videos into one :

  ffmpeg -c:v libvpx -i a1.mkv -c:v libvpx -i a2.mkv -c:v libvpx -i a3.mkv -c:v libvpx -i 4.mkv -filter_complex "[1]setpts=PTS+5.00/TB[a2];[2]setpts=PTS+10.00/TB[a3];[3]setpts=PTS+15.00/TB[a4];[0][a2]overlay[o2];[o2][a3]overlay[o3];[o3][a4]overlay" out.mp4

  The problem I am facing is that there is a gost text from previous video which is seen on the next video (image attached for reference)

  I am totaly lost in how to rectify this issue. Please advise.

• Process GIF using FFmpeg libraries - can't find parser at av_parser_init

  24 novembre 2018, par natario

  I am playing with ffmpeg libs, namely libswscale and libavcodec for now. My goal is resize GIF files. From my ridiculous understanding, I think I need to

  • decode the GIF and get an AVFrame
  • process the frame with libswscale
  • encode again into GIF

  But I am stuck at step 1. Based on official sample at https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/decode_video.c , I need to get a parser :

  codec = avcodec_find_decoder(AV_CODEC_ID_GIF);
  
  parser = av_parser_init(codec->id);

  But no parser is found. I am not touching parser in my configure call, so I take all :

  Enabled parsers:
  
  aac                       cavsvideo                 dvbsub                    h263                      mpegvideo                 sipr                      xma
  
  aac_latm                  cook                      dvd_nav                   h264                      opus                      tak
  
  ac3                       dca                       dvdsub                    hevc                      png                       vc1
  
  adx                       dirac                     flac                      mjpeg                     pnm                       vorbis
  
  av1                       dnxhd                     g729                      mlp                       rv30                      vp3
  
  avs2                      dpx                       gsm                       mpeg4video                rv40                      vp8
  
  bmp                       dvaudio                   h261                      mpegaudio                 sbc                       vp9

  What am I doing wrong ? If this is the wrong approach, what is the correct one ?

• Pass ID3D11Texture2D back buffer to libx264 encoder

  17 janvier 2019, par Chris Sixsmith

  I’m writing a C++ program to encode frames from a DirectX game to the H.264/MPEG-4 AVC format. I am using libx264 alone with no other dependencies at the moment.

  I have a ID3D11Texture2D* resolved back buffer of the next game frame. I need to somehow copy this into the x264_picture input (apparently YUV420P format according to limited help I’ve found) but I cannot find any way to do so online.

  Here is my code at the moment :

  void Fx264VideoEncoder::Fx264VideoEncoderImpl::InitFrameInputBuffer(const FTexture2DRHIRef& BackBuffer, FFrame& Frame)
  
  {
  
      x264_picture_alloc(Frame.InputPicture, X264_CSP_I420, x264Parameters.i_width, x264Parameters.i_height);
  
  
  
      // We need to take the back buffer and convert it to an input format that libx264 can understand
  
      {
  
          ID3D11Texture2D* ResolvedBackBufferDX11 = (ID3D11Texture2D*)(GetD3D11TextureFromRHITexture(Frame.ResolvedBackBuffer)->GetResource());
  
          EPixelFormat PixelFormat = Frame.ResolvedBackBuffer->GetFormat();
  
  
  
          // ...?
  
      }
  
  }