How this tool works
One video becomes two files: the picture with no sound, and the sound as an MP3. Both are produced on your own device, so nothing is uploaded.
For MP4 files the picture is copied across exactly as it was, without being decoded or encoded again, so there is no loss of quality at all and it takes seconds rather than minutes. The timing is carried over precisely, so the two files line up again if you put them back together in an editor. Other formats have to be re-encoded, which is slower and costs a little quality; the tool says so before it starts.
What people use it for
- Editing the sound separately: clean up, level or replace the audio in a sound editor, then bring the two back together — the untouched picture is waiting.
- Reusing footage with new music: the silent video is ready for a different soundtrack, and the original audio is kept rather than thrown away.
- Keeping the audio of a talk: the MP3 plays anywhere a podcast does, and the video is still there if the slides are needed later.
- Quality applies to the MP3 only: the setting chooses the MP3 bitrate. The video is never recompressed when the source is MP4.