Thumbnail generator from video file

[hdsdi3g]

• [x] Best effort for short and long files
• [x] And at precise ~frame number~ PTS
• [x] Extract embedded image - postponed to https://github.com/hdsdi3g/medialib/issues/110

Base command line:

ffmpeg -y -ss "$1" -skip_frame nokey -i "$2" -map_metadata -1 -an -vsync vfr \
    -vf "thumbnail=10,bwdif=deint=1,format=yuv420p,scale=w=trunc(ih*dar/2)*2:h=trunc(ih/2)*2:out_color_matrix=bt709:out_range=jpeg,setsar=1:1" \
    -frames:v 1 -codec:v mjpeg -qscale:v 1 -huffman optimal \
    snap.jpg

• [x] One call = one image
• [x] Always produce program fullsize images, 1/1 SAR
• [x] Create on I frames (best effort)
• [x] Deinterlace if needed
• [x] HDR to SDR jpeg
• [x] HQ jpeg

[hdsdi3g]

https://www.bannerbear.com/blog/how-to-set-a-custom-thumbnail-for-a-video-file-using-ffmpeg

https://www.bannerbear.com/blog/how-to-extract-images-from-a-video-using-ffmpeg/

-ss position (input/output)
When used as an input option (before -i), seeks in this input file to position. Note that in most formats it is not possible to seek exactly, so ffmpeg will seek to the closest seek point before position. When transcoding and -accurate_seek is enabled (the default), this extra segment between the seek point and position will be decoded and discarded. When doing stream copy or when -noaccurate_seek is used, it will be preserved.

When used as an output option (before an output url), decodes but discards input until the timestamps reach position.

position must be a time duration specification, see [(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual](https://www.ffmpeg.org/ffmpeg-utils.html#time-duration-syntax).