FFmpeg

## Convert mp4 to webm
ffmpeg -i input.mp4 output.webm

## Convert gif to mp4
ffmpeg -i input.gif -movflags faststart -pix_fmt yuv420p output.mp4

## 指定時間でカット
ffmpeg -i input.mp4 -t 10.0 -c copy output.mp4
ffmpeg -i input.mp4 -ss 00:01:00 -to 00:02:00 -c copy output.mp4

## 入力FPSを変更 = 再生時間が変わる
ffmpeg -r 30 -i input.gif -movflags faststart -pix_fmt yuv420p output.mp4

## 出力FPSを変更 = 再生時間は変わらない
ffmpeg -i input.gif -movflags faststart -pix_fmt yuv420p -r 30 output.mp4

https://trac.ffmpeg.org/wiki/colorspace
https://www.reddit.com/r/ffmpeg/comments/o00ymo/help_iphone_hevc_file_converted_to_h264_has_color/
https://zenn.dev/razokulover/scraps/4282a6911e4ca7
https://apple-log.work/2021/12/24/

特に何も指定せずMOVを変換すると白飛びしてしまう

ffmpeg -i input.mov output.webm

以下の様にColorspaceの調整などで対応は可能だが、特にこだわりがなければVLCの変換機能などを利用した方が簡単

ffmpeg -i input.mov output.webm -pix_fmt yuv420p -vf "eq=brightness=0.0:saturation=1.0:contrast=1.0:gamma=1.0"

https://blog.curegit.jp/posts/tools/image-processing/ffmpeg-snippets/

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