Search code examples
windowsffmpeg

Remove error when running ffmpeg in Windows script to shrink MP3 file

I use a script to downsize audiobook files.
The original audiobook file was concatenated from multiple MP3 files into one MP3 file.
The script (in Windows) relies on ffmpeg (version git-2020-06-26-7447045) and contains

FOR %%A IN (dir *.mp3) DO ffmpeg -i "%%A" -c:a libmp3lame -q:a 8 "_%%A"

However, this error message appears:

deprecated pixel format used, make sure you did set range correctly
[mp3 @ 000001f026d56400] Frame rate very high for a muxer not efficiently supporting it.
Please consider specifying a lower framerate, a different muxer or -vsync 2

How do I modify the script for greater efficiency and remove that error message?

Solution

  • Stream copy album art instead of re-encoding it:

    FOR %%A IN (dir *.mp3) DO ffmpeg -i "%%A" -c:v copy -c:a libmp3lame -q:a 8 "_%%A"

    Other, unrelated suggestions:

    • Add -ac 1 if you want to make the outputs mono to save space (assuming the inputs are stereo).
    • Consider using Opus (-c:a libopus) instead of MP3 if you want to use a modern, very efficient encoder for lower bitrates.