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• 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 !

  


• ffmpeg : combine portrait and landscape video files in one file by adding a black frame

  18 juillet 2021, par Oliver

  i use my iPhone to record videos. Usually i get a lot of short clips, which I upload to my pc and then concatenate them with ffmpeg using this command :

  


  ffmpeg -f concat -safe 0 -i filelist.txt -c:v libx265 -preset slow -x265-params strong-intra-smoothing=0:merange=58 -crf 25 -c:a aac -b:a 320k -tag:v hvc1 output.mp4


  


  filelist contains a list of these clips sorted by date. This works fine, but recently a had some clips recorded in portrait mode. The result was an output video which contained the portrait clips stretched to fill the full horizontal space. Instead of that i would like to just have the horizontal space filled with black borders. Is that possible by changing the command posted above ? Or do i have to convert those portrait clips before ?

  


• ffmpeg vaapi - scale a video keeping the aspect ratio and padding with black lines

  26 décembre 2022, par Rusty Lemur

  I'm trying to use my Vega 11 GPU to perform hardware accelerated transcoding of some video files to a resolution of 1280x720. I would like to keep the original aspect ratio and add black bars to the borders as necessary. I can get the scaling to work with the following :

  


  ffmpeg -hwaccel vaapi -hwaccel_output_format vaapi -vaapi_device /dev/dri/renderD128 -i input.mp4 -codec:v h264_vaapi -vf scale_vaapi=w=1280:h=720,setsar=1:1 output.mp4


  


  But some of the image gets stretched with that, and the original aspect ratio is not preserved.

  


  On the Raspberry Pi I can get the effect I want with the following :

  


  ffmpeg -i input.mp4 -b:v 2M -vf scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:'(ow-iw)/2':'(oh-ih)/2',setsar=1 -vcodec h264_v4l2m2m -num_capture_buffers 128 output.mp4


  


  But when I try to use the force_original_aspect_ratio and pad options with the vaapi codec, I get the following error :

  


  ffmpeg -hwaccel vaapi -hwaccel_output_format vaapi -vaapi_device /dev/dri/renderD128 -i input.mp4 -codec:v h264_vaapi -vf scale_vaapi=w=1280:h=720,pad=1280:720:'(ow-iw)/2':'(oh-ih)/2',setsar=1:1 output.mp4

Impossible to convert between the formats supported by the filter 'Parsed_scale_vaapi_0' and the filter 'auto_scaler_0'
Error reinitializing filters!
Failed to inject frame into filter network: Function not implemented
Error while processing the decoded data for stream #0:0


  


  Is there another option I should use to get the padding and keep the original aspect ratio ?