This is a bat file that transcodes all audio files in a directory into `.opus` files. I use this neat script to sync my `.flac` library with my mobile library.

convert_to_opus.bat

@echo off

rem Copies the original directory structure from F:\Music to D:\Music
rem xcopy /T %1 %2

Robocopy %1 %2 /E /XF *.flac *.mp3 *.mp4

for /R %1 %%i in (*.flac;*.mp3;*.mp4) do (

    rem check if file exists
    if exist "%~d2%%~pni.opus" (

        echo "%~d2%%~pni.opus" already exists

    ) else (

        echo Converting "%%~fi"

        rem convert to opus

        ffmpeg -v quiet -i "%%~fi" -map 0:a:0 -map_metadata 0 -c:a libopus -b:a 128k -frame_duration 20 "%~d2%%~pni.opus"
    )
)
echo Done
pause

@echo off
setlocal EnableDelayedExpansion

:: Ask for source and destination directories
set /p SRC="Enter the source directory (e.g., F:\Music): "
set /p DEST="Enter the destination directory (e.g., D:\Music): "

:: Copy directory structure (excluding files)
robocopy "%SRC%" "%DEST%" /E /XF *.flac *.mp3 *.mp4 *.opus /CREATE

:: Loop through all audio files
for /R "%SRC%" %%i in (*.flac *.mp3 *.mp4) do (

    set "srcfile=%%i"
    set "relpath=%%~pi"
    set "filename=%%~ni"

    set "outfile=%DEST%!relpath!!filename!.opus"

    if exist "!outfile!" (
        echo "!outfile!" already exists
    ) else (
        echo Converting "%%i"
        ffmpeg -v quiet -i "%%i" -map 0:a:0 -map_metadata 0 -c:a libopus -b:a 128k -frame_duration 20 "!outfile!"
    )
)

echo Done
pause