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• How can i transform dvb subtitles into text format using FFMpeg within a live streaming or how can i optimize the dvb burning process ?

  5 décembre 2018, par alexsua

  I am working on a hls transcoder from any format to HLS and I need to encode multiple subtitles with the format "dvbsub" at the same time with the purpose of being selected by a client who interprets the m3u8 HLS playlist.

  The main problem is that burning each dvbsub into a live video stream in this way :

   "-filter_complex "[0:v][0:s:0]overlay[v0];[0:v][0:s:1]overlay[v1];[0:v][0:s:2]overlay[v2];......"

  is a very CPU intensive task. (I have 8 or more dvbsub in the same stream).

  Does Anyone know how to transform each dvbsub into a text format (webvtt for example) or if there is a way to optimize the process ? (I tried to perform this burning process with NVIDIA gpu but I have not achieved any improvement)

  I read about OCR programs which can do the task but after days of research i still dont know how to do that.

  Thanks in advance.

  EDIT : The input is a live UDP signal. I need to do the transformation on the fly.

• FFMPEG Screen record using AMD GPU encoder in Arch linux

  23 décembre 2020, par Lucas Martins Soares

  I am trying to record my screen with the GPU encoder using the following command :

  


  ffmpeg -vaapi_device /dev/dri/renderD128 -f x11grab -video_size 1440x900 -i :0 -vf 'hwupload,scale_vaapi=format=nv12' -c:v h264_vaapi -qp 24 output.mp4

  


  But I get the following error :

  


  [h264_vaapi @ 0x565330f47580] Driver does not support some wanted packed headers (wanted 0xd,
found 0x1).

  


  the recording starts well but when i finish a 3 second video it takes 3 minutes to process and the
result is an almost slow motion video.

  


  My drivers :

  


  xf86-video-amdgpu 19.1.0-2
xf86-video-ati 1:19.1.0-2
xf86-video-fbdev 0.5.0-2
xf86-video-vesa 2.5.0-1
libva-mesa-driver 20.3.1-1
mesa 20.3.1-1
opencl-mesa 20.3.1-1


  


  vainfo :

  


  
vainfo: VA-API version: 1.10 (libva 2.10.0)
vainfo: Driver version: Mesa Gallium driver 20.3.1 for AMD VERDE (DRM 2.50.0, 5.9.14-arch1-1, LLVM 11.0.0)
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            : VAEntrypointVLD
      VAProfileMPEG2Main              : VAEntrypointVLD
      VAProfileVC1Simple              : VAEntrypointVLD
      VAProfileVC1Main                : VAEntrypointVLD
      VAProfileVC1Advanced            : VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileH264High               : VAEntrypointVLD
      VAProfileH264High               : VAEntrypointEncSlice
      VAProfileNone                   : VAEntrypointVideoProc



  


• FFMPEG extracting frames is slow even with CUDA

  5 juin 2023, par Ξένη Γήινος

  I have a bunch of videos at some location that I want to extract frames from.

  


  The videos are of .wmv format, and have a framerate of 25, and I want to extract all frames from them losslessly.

  


  And I do have a dedicated graphics card (NVIDIA Geforce GTX 1050 Ti, I know it's old), so I want to utilize it to accelerate frame extraction. I downloaded FFMPEG with CUDA support from www.gyan.dev for exactly this.

  


  I came up with this PowerShell command :

  


  gci C:\Users\Xeni\Documents -filter *.wmv | %{
 $folder = 'C:\Users\Xeni\Desktop\' + $($_.name -replace '.wmv')
 md $folder;
 D:\ffmpeg\ffmpeg.exe -hwaccel cuda -i $_.fullname -vf fps=25 "$folder\%05d.bmp"
}


  


  But somehow it is slow, its disk write speed is less than 100 MiB/s and it uses less than 1% GPU, and it takes about 2 seconds to process 25 frames.

  


  How can I speed up this command ?