You could use the following ffmpeg command line:
ffmpeg -i video.mkv -map 0:v -map 0:m:language:eng -codec copy video_2.mkv
Explanation:
-i video.mkv input file (identified as '0:' in mappings below) -map 0:v map video streams from input to output file -map 0:m:language:eng map streams for language 'eng' from input to output file (may be specified multiple times for multiple languages) -codec copy copy streams without reencoding video_2.mkv output file
The resulting file will retain streams for English only (except for video streams which are copied regardless).
I actually even created a script for this a while ago (GitHub Gist: remove-unneeded-languages.sh):
#!/usr/bin/env bash # ------------------------------------------------------------------------- # - # Remove unneeded language(s) from video file - # - # Created by Fonic <https://github.com/fonic> - # Date: 04/14/22 - 08/26/22 - # - # Based on: - # https://www.reddit.com/r/ffmpeg/comments/r3dccd/how_to_use_ffmpeg_to_ - # detect_and_delete_all_non/ - # - # ------------------------------------------------------------------------- # Print normal/hilite/good/warn/error message [$*: message] function printn() { echo -e "$*"; } function printh() { echo -e "\e[1m$*\e[0m"; } function printg() { echo -e "\e[1;32m$*\e[0m"; } function printw() { echo -e "\e[1;33m$*\e[0m" >&2; } function printe() { echo -e "\e[1;31m$*\e[0m" >&2; } # Set up error handling set -ue; trap "printe \"Error: an unhandled error occurred on line \${LINENO}, aborting.\"; exit 1" ERR # Process command line if (( $# != 3 )); then printn "\e[1mUsage:\e[0m ${0##*/} LANGUAGES INFILE OUTFILE" printn "\e[1mExample:\e[0m ${0##*/} eng,spa video.mkv video_2.mkv" printn "\e[1mExample:\e[0m for file in *.mkv; do ${0##*/} eng,spa \"\${file}\" \"out/\${file}\"; done" printn "\e[1mNote:\e[0m LANGUAGES specifies language(s) to KEEP (comma-separated list)" exit 2 fi IFS="," read -a langs -r <<< "$1" infile="$2" outfile="$3" # Sanity checks [[ -f "${infile}" ]] || { printe "Error: input file '${infile}' does not exist, aborting."; exit 1; } command -v "ffmpeg" >/dev/null || { printe "Error: required command 'ffmpeg' is not available, aborting."; exit 1; } # Run ffmpeg printh "Processing file '${infile}'..." lang_maps=(); for lang in "${langs[@]}"; do lang_maps+=("-map" "0:m:language:${lang}"); done ffmpeg -i "${infile}" -map 0:v "${lang_maps[@]}" -codec copy -loglevel warning "${outfile}" || exit $? exit 0
Use it like this (e.g. to process all .mkv files and only keep streams for English and Spanish):
mkdir out; for file in *.mkv; do remove-unneeded-languages.sh eng,spa "${file}" "out/${file}"; done
