Got it, let's tweak your existing FFmpeg batch command to preserve the original 5.1 audio tracks while adding your normalized 2.0 stereo track. Here's the breakdown and modified command:

Key Changes Explained #

Your original command was converting all input audio tracks directly to 2.0. To keep both the original and new track, we need to:

1. Copy the original 5.1 audio tracks without modification
2. Generate a new normalized 2.0 track from the original audio
3. Ensure both tracks are included in the output MKV

Modified Batch Command #

for /r %%i in (*.mkv) do (
    @ffmpeg.exe -hide_banner -v 32 -stats -y -i "%%i" ^
    -map 0:v -c:v copy ^
    -map 0:a -c:a:0 copy ^
    -map 0:a -acodec ac3 -ac 2 -ar 48000 -ab 640k -af %aproc2% -c:a:1 ac3 ^
    -map 0:s? -c:s copy ^
    -f matroska "%%~ni [Stereo+5.1].mkv"
)

What Each Part Does #

• -map 0:v -c:v copy: Copies the original video stream unchanged (same as your original command)
• -map 0:a -c:a:0 copy: Maps the original audio tracks (your 5.1 channels) and copies them directly without encoding
• -map 0:a -acodec ac3 -ac 2 -ar 48000 -ab 640k -af %aproc2% -c:a:1 ac3: Maps the original audio again, applies your normalization filter (%aproc2%), converts it to 2.0 stereo AC3 with your specified bitrate/sample rate, and marks this as the second audio stream
• -map 0:s? -c:s copy: Copies all subtitle streams (if present) unchanged
• The output filename is updated to [Stereo+5.1] to clearly indicate both track types are included

Quick Notes #

• If you have multiple original 5.1 tracks, this command will copy all of them and add a normalized 2.0 track for each. If you only want one 2.0 track (e.g., derived from the first audio stream), adjust the second -map 0:a to -map 0:a:0 instead.
• Double-check that %aproc2% is properly defined in your batch environment (it should contain your audio normalization filter string, like loudnorm=I=-16:LRA=11:TP=-1.5 or similar).

内容的提问来源于stack exchange，提问作者aur0n