OLD - FFMPEG - Add AC3 audio stream while keeping original video, audio, subtitles

FFMPEG - Add AC3 audiostream.cmd

:: below command will retain original audio stream and then create 2nd stream encoded in ac3
:: move ffmpmeg to c:\windows\system32
:: -vf "crop=trunc(iw/2)*2:trunc(ih/2)*2" command added to avoid errors with cropping
:: this will retain all prev audio streams and just add a new ac3 stream (converts first audio stream to ac3)
:: 
:: THIS does take a LONG TIME and would not recommend this method, use my extract audio as ac3 for fastest way!
:: Also my mapping may be messed up on this one too, def test on test files first!
::----------------------------------------
setlocal EnableExtensions DisableDelayedExpansion
::get filename and extensions as variables
set _name=%~n1
set _ext=%~x1

::add ac3 audio track

ffmpeg -i "%_name%%_ext%" -vf pad="width=ceil(iw/2)*2:height=ceil(ih/2)*2" -map 0:v -map 0:a -map 0:s? -c:a copy -map 0:a:0 -c:a:0 ac3 -b:a 640k -center_mixlev 0.707 -c:s copy "%_name%.NEW%_ext%"

FYI: eac audio streams do not convert to ac3, remain eac. as a workaround here is what i do:

use eac3to to extract EAC file as ff-ac3, then use mkvtoolnix to add ac3 file back to original file (be sure to set compress = no so it will copy streams as is)

updated: this will now work with aac files, does take a while to process. eac3 streams still need to use above workaround with eac3to and mkvtoolnix.

this method is WAY TOO time consuming, i have created a new gist that uses ffmpeg and mkvtoolnix, avg time to extrac ac3 file and then multiplex is around 3 mins vs this one that takes up to 30 mins!!