✂️ trim.lua

mpv script to create a "precise" clip of audio / video files without transcoding.

❓ Differences from the other similar scripts

• trim.lua is aimed only for extraction of clips with no-transcoding. Encodings will never be occured.
• Without encoding, video trimming becomes tricky.
  • Without transcoding, points you can specify to trim is limited to keyframes.
  • Tested several softwares on macOS and as far as I know there is no software that can do it accurately. Well, there is, but none were perfect nor lightweight.
  • This script is here to achieve accuracy as much as possible — Making a clip from a file within minimum keyframe distance, without transcoding.

In short, trim.lua turns mpv into a simple lossless audio / video editor.

📦 Install

# macOS, *nix
curl https://raw.githubusercontent.com/aerobounce/trim.lua/master/trim.lua >> ~/.config/mpv/scripts/trim.lua

• If your shell has PATH to ffmpeg you're ready to use.
  • If not, rewrite ffmpeg_bin accordingly.
• All Windows users likely have to specify full path to ffmpeg.
  • Or copy the standalone binary into the script directory (not tested).

trim.lua

-- macOS, *nix
ffmpeg_bin = "ffmpeg"

-- Windows
ffmpeg_bin = "ffmpeg.exe"

⚠️ Requirements

• ffmpeg

✂️ Usage

Enable trim mode

• h or k

If initialized with h, default trim positions will be: Current time position to End of file.
If initialized with k, default trim positions will be: Head of file to Current time position.

Toggle strip metadata mode (After initializing trim mode)

Stripping metadata can fix certain corrupted files.

• t

Save Trim Positions

To write out a clip, press either of the keys twice with the same start / end position.
To quit Trim Mode, close mpv instance.

• h Save Trim Start Keyframe
• k Save Trim End Position

Seeking

Seek to saved positions

• shift + h Seek to the saved Trim start position
• shift + k Seek to the saved Trim end position

With video file

• LEFT Seek backward by keyframe (Minimum distance)
• RIGHT Seek forward by keyframe (Minimum distance)
• UP Seek forward by keyframe (Larger distance)
• DOWN Seek backward by keyframe (Larger distance)
• shift+LEFT Seek backward exactly by seconds (-0.1 seconds)
• shift+RIGHT Seek forward exactly by seconds (0.1 seconds)
• shift+UP Seek backward exactly by seconds (0.5 seconds)
• shift+DOWN Seek forward exactly by seconds (-0.5 seconds)

With audio file

• LEFT Seek backward by seconds (-1 seconds)
• RIGHT Seek forward by seconds (1 seconds)
• UP Seek forward by seconds (5 seconds)
• DOWN Seek backward by seconds (-5 seconds)
• shift+LEFT Seek backward by seconds (-10 seconds)
• shift+RIGHT Seek forward by seconds (10 seconds)
• shift+UP Seek forward by seconds (30 seconds)
• shift+DOWN Seek backward by seconds (-30 seconds)

ℹ️ To create a valid video file

• Beggining of the trim position must be a keyframe.
• End position can be any point.

🗜 Concat with ffmpeg

After splitting, you can concat them with a script something like this.

CLIPS=("example_1.mp4" "example_2.mp4")
DESTINATION="concat_example.mp4"

ffmpeg \
    -hide_banner \
    -loglevel verbose \
    -f concat \
    -safe 0 \
    -auto_convert 0 \
    -err_detect ignore_err \
    -i <(
        while read -r; do
            echo "file '$REPLY'"
        done <<< "${CLIPS[*]}"
    ) \
    -copy_unknown \
    -map_chapters 0 \
    -c copy \
    "$DESTINATION"

Known Issue

• Any embedded media other than video / audio will be lost, such as embedded subtitles. This will unlikely be fixed.