ffmpeg wrapper to customely downmix videos opened by jellyfin

ffmpeg

#!/bin/bash -
#title           :ffmpeg
#description     :This script is a wrapper for jellyfin ffmpeg to downmix audio to stereo using a custom formula
#author          :Daniel Fomin
#date            :20230104
#version         :0.2
#reference       :https://superuser.com/questions/852400/properly-downmix-5-1-to-stereo-using-ffmpeg
#
#
#==============================================================================

###############################################################################
# Installation Notes: 
#   1. Put wrapper in directory accessible from jellyfin
#   2. `chmod +x path/to/wrapper/dir/ffmpeg`
#   3. `ln -s $(which ffprobe) path/to/wrapper/dir/` to the same directory
#   4. Point jellyfin to the wrapper directory
#
###############################################################################

function join { local IFS=$'\n'; echo "${*}"; }

args=$(join "${@}")

match='-ac\n[3-9]'
replace='-af\npan=stereo|FL<0.707*FC+0.707*FL+0.707*BL+0.5*LFE|FR<0.707*FC+0.707*FR+0.707*BR+0.5*LFE'
ffmpeg="/usr/lib/jellyfin-ffmpeg/ffmpeg"

readarray -t new_args < <(sed -z "s/$match/$replace/g" <<<"$args")

#echo "Command Rewrite: $ffmpeg $new_args" 1>&2

$ffmpeg "${new_args[@]}"
exit $?

I'll leave here an improved version or the wrapper script, with proper handling of quotes

#!/bin/bash -
#title           :ffmpeg wrapper
#description     :This script is a wrapper for jellyfin ffmpeg to replace arguments
#==============================================================================

ffmpeg="/usr/lib/jellyfin-ffmpeg/ffmpeg"

#Add quotes for arguments with "spaces" and "round brackets")
for x in "${@}" ; do
    # try to figure out if quoting was required for the $x (Arguments)
    if [[ "$x" != "${x%[[:space:]]*}" ]] \
    || [[ "$x" != "${x%(*}" ]] ; then
        x="\""$x"\""
    fi
    _args=$_args" "$x
done

# Downmix audio to stereo
_args=${_args/-ac [3-9]/-af \"pan=stereo|FL < 0.5*FC + 0.3*FLC + 0.3*FL + 0.3*BL + 0.3*SL + 0.5*LFE | FR < 0.5*FC + 0.3*FRC + 0.3*FR + 0.3*BR + 0.3*SR + 0.5*LFE,volume=2\"}

eval $ffmpeg $_args

exit $?

Thanks for this was trying to write something similar - your foo is much stronger than my bar!

Couple of notes for future noobish users like myself

the "ln -s" command creates a symbolic link for ffprobe - my unraid docker container didn't recognise the "which" command, I had to use:

ln -s /usr/lib/jellyfin-ffmpeg/ffmpeg/ffprobe /config/

where I placed the script in the config directory

another nooby issue is that i forgot to set permissions:

chmod u=rwx,g=rwx,o=rwx /config/ffmpeg

Hope this helps someone!

Thank you @mark-cassidy for your remarks, I have added the chmod command to the installation notes.

Real noob question, but I stumbled upon your script and I am wondering if it is possible to use it somehow in Windows, as currently I am experiencing issues with Jellyfin and 5.1 audio, and want to force downmixing to stereo of everything that is being played.

Unless you’re running Jellyfin inside a docker container the answer is no. This script basically takes the command Jellyfin uses to call ffmpeg and swaps out the commands in Linux.

On Sun, 22 Jan 2023 at 14:27, ivaylo-mk ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ Real noob question, but I stumbled upon your script and I am wondering if it is possible to use it somehow in Windows, as currently I am experiencing issues with Jellyfin and 5.1 audio, and want to force downmixing to stereo of everything that is being played. — Reply to this email directly, view it on GitHub <https://gist.github.com/e79d223d0cb439fadd868edccce9a172#gistcomment-4445163> or unsubscribe <https://github.com/notifications/unsubscribe-auth/AMNIULS2RS2J6ETBR3JCUMDWTU7VXBFKMF2HI4TJMJ2XIZLTSKBKK5TBNR2WLJDHNFZXJJDOMFWWLK3UNBZGKYLEL52HS4DFQKSXMYLMOVS2I5DSOVS2I3TBNVS3W5DIOJSWCZC7OBQXE5DJMNUXAYLOORPWCY3UNF3GS5DZVRZXKYTKMVRXIX3UPFYGLK2HNFZXIQ3PNVWWK3TUUZ2G64DJMNZZDAVEOR4XAZNEM5UXG5FFOZQWY5LFVEYTCMBUGQ2TMOBXU52HE2LHM5SXFJTDOJSWC5DF> . You are receiving this email because you commented on the thread. Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub> .

-- -- Mark Cassidy ***@***.***