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• doc : fix one accented word

  24 février 2014, par Vittorio Giovara

  doc : fix one accented word
  

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• Révision 21338 : Report de c21337 : Ne pas confondre le Kazakh (kk - http://fr.wikipedia.org/wiki...

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• How to preserve colours when colour metadata is "unknown"

  5 avril 2024, par Hashim Aziz

  I often need to scale up many files with unknown color metadata (probably because FFmpeg itself was dropping that metadata until very recently) :

  


  $ ffprobe -v error -show_streams "input.mp4" | grep color

color_range=tv
color_space=unknown
color_transfer=unknown
color_primaries=unknown


  


  No matter what I do to try and preserve the colours in these files, nothing works to prevent the colours from shifting, usually coming out darker than the input.

  


  I've already tried :

  


  


  1. Setting all four color metadata options (-colorspace, -color_trc, -color_primaries, -color_range) to all of their possible values for PAL, NTSC and HD inputs (bt470bg, smpte170m and bt709 respectively)

     


  


  2. Automatically converting the colorspace as part of the scale by adding in_color_matrix=auto:out_color_matrix=<colorspace></colorspace>, where is either bt470, smpte170m or bt709

     


  


  3. Explicitly converting the colorspace as part of the scale by adding in_color_matrix=<colorspace>:out_color_matrix=bt709</colorspace>, where is either bt470, smpte170m or bt709

     


  


  


  After all of this, I'm still left none the wiser as to how the hell colour works in FFmpeg and what I'm meant to be doing just to get my colour to look as it does in the original input.

  


  Here is the (simplified) FFmpeg command that I'm running as part of a larger script, most of which is probably irrelevant to the issue but which I've included in case it isn't :

  


  ffmpeg -y -hide_banner \
-i "input.webm" -i "outro.mp4" -loop 1 -i "watermark.png" \
-movflags +faststart+write_colr \ 
-filter_complex \
"color=black:16x16:d=780[base];
[0:v]scale=1922:'max(1080,ih)':flags=lanczos:in_color_matrix=auto:out_color_matrix=bt709[v0];
[1:v]scale=1922:'max(1080,ih)':flags=lanczos,fade=in:st=0:d=2:alpha=1[v1];
[2:v]lut=a=val*0.7,fade=in:st=15:d=3:alpha=1,fade=out:st=775:d=3:alpha=1[v2];
[base][v0]scale2ref[base][v0];
[base][v0]overlay[tmp];
[tmp][v1]overlay,setsar=1[tmp2];
[v2][tmp2]scale2ref=w=oh*mdar:h=ih*0.07[watermark_scaled][video]
[video][watermark_scaled]overlay=80:50:shortest=1:format=rgb[outv];
[0:a]afade=out:st=778:d=2[0a];
[0a][1:a]concat=n=2:v=0:a=1[outa]" \
-map "[outv]" -map "[outa]" -c:v libx264 -crf 15 -c:a libopus \
-pix_fmt yuv420p -colorspace bt709 -color_trc bt709 -color_primaries bt709 -color_range tv "output.mp4"