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• ffmpeg puts black frames in the first few seconds of the video

  30 juin 2018, par Joe T. Boka

  I am adding an audio file to a video file, using ffmpy, which is a python wrapper for ffmpeg.

  The input audio file voice.wave and the input video file video.avi are the same length.

  When I use the below code, the output video output.ts contains both audio and video, as expected. The problem : the audio is running fine, but the first few seconds of the output video output.ts is black.

  from ffmpy import FFmpeg
  
  ff = FFmpeg(inputs={'video.avi': None, 'voice.wav': None}, outputs={'output.ts': '-c:v h264 -c:a ac3'})
  
  ff.cmd
  
  'ffmpeg  -i voice.wave -i video.avi -c:v h264 -c:a ac3 output.ts'
  
  ff.run()

• ffmpeg video encode add artefacts on very dark scenes (near to black)

  10 juin 2021, par Marco999

  I have many videos ripped from blu ray (h.264).

  


  I don't have sufficient space to store all videos and I like to re-encode all video with hevc codec (h.265) and keep similar quality (not exactly the some) but with a good compromise.

  


  I have tried this command :

  


  ffmpeg.exe -hide_banner -hwaccel nvdec -hwaccel_device 0 -vsync 0 -i "title00.mkv" -c:s copy -an  -c copy -c:v:0 hevc_nvenc -profile:v main10 -pix_fmt p010le  -rc-lookahead 32 -spatial-aq 1 -aq-strength 12  -cq 30 -qmin 1 -qmax 30 -b:v:0 10M -maxrate:v:0 20M -gpu 0  title00_nvidia_no_audio.mkv


  


  the quality is excellent and is very close to original, but on the very dark scenes (near to black) there are visible artefacts.

  


  To solve the problem I have tried this changes without get any improvement :

  


  -cq 25 -qmin 1 -qmax 25 

-spatial-aq 1 -aq-strength 4


  


  For some strange reason seem that if I decrease the -cq from 30 to 25 the artefacts are more visible.

  


  I general I'am satasfied about the quality result but before start the encoding I like to understand if there is a way to reduce/remove these artefacts on very dark scenes.

  


  Any tips ?

  


  Thanks !

  


• How to automatically remove black bars using ffmpeg from a Powershell script ?

  27 avril 2021, par timlwsk

  Thanks to the help of the user mklement0 I got this script to automatically convert all files in the folder "video_old" and move them into "video_new", all while keeping the original filename. Original Post.

  



  Now I want to remove the black bars in the container. I know that there is "cropdetect" but AFAIK you have to manually parse the the value into the script. What parameter should I add to bellow's ffmpeg execution ?

  



  Get-ChildItem .\video_old -Filter *.mkv | ForEach-Object {
  .\ffmpeg.exe -i $_.FullName -c:v libx265 -crf 18 ".\video_new\$($_.Name)"
}


  



  Parameters used to remove the bars

  



  ffmpeg -ss 90 -i input.mkv -vframes 10 -vf cropdetect -f null -
...
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:215 t:0.215000 crop=1280:720:0:0
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:257 t:0.257000 crop=1280:720:0:0
[Parsed_cropdetect_0 @ 0x220cdc0] x1:0 x2:1279 y1:0 y2:719 w:1280 h:720 x:0 y:0 pts:299 t:0.299000 crop=1280:720:0:0


  



  In this example, we can apply the filter like this :

  



  ffmpeg -i input.mkv -vf crop=1280:720:0:0 -c:a copy output.mkv


  



  OriginalPost

  



  Screenshot