ffmpeg

One-liners

Detect encoding errors

ffmpeg -err_detect explode -i <infile> -f null -

Convert music file to Opus format

find . -type f -name '*.flac' | parallel 'test -f {.}.opus || ffmpeg -i {} -vn -c:a libopus -b:a 192k {.}.opus'

Keep display aspect ratio when downsampling

ffmpeg -i in.mp4 -vf "setsar='if(sar,sar,1)',scale=640x480" out.mp4

Scripts

Video transcribe with whisper.cpp

Tips: if no copyright issues are involved, you could also upload videos to YouTube and let it auto transcribe them for you.

#!/usr/bin/env bash
set -euo pipefail
 
MODEL="$HOME/.local/share/whisper-cpp/ggml-base.en.bin"
 
if [ $# -lt 1 ]; then
  echo "Usage: ${0##*/} <input> [output.srt]" >&2
  exit 1
fi
 
input="$1"
output="${2:-${input%.*}.srt}"
 
if [ -e "$output" ]; then
  printf '%s already exists. Remove it? [y/N] ' "$output"
  read -r answer
  case "$answer" in
    [yY]*) rm "$output" ;;
    *) exit 0 ;;
  esac
fi
 
tmpout=$(mktemp "${TMPDIR:-/tmp}/transcribe-XXXXXX")
trap 'rm -f "$tmpout"' EXIT
 
ffmpeg -i "$input" -vn -af \
  "whisper=model=${MODEL}:language=en:queue=20:destination=${tmpout}:format=srt" \
  -f null -
 
mv -i "$tmpout" "$output"