Replace Video Audio

About this tool

Choose the video and the sound you want on it (MP3, WAV, M4A, OGG and other audio files). The picture of the video is copied as it is, so there is no loss of quality and it is quick; the new sound is encoded as AAC at 192 kbit/s, which every player understands, and the old sound is removed. Decide how long the result is: the same as the video, cutting a longer sound and leaving silence after a shorter one; the same as the video with a shorter sound repeated over and over; or the shorter of the two. We checked each combination of a longer and a shorter sound with each length rule and measured the result: the video stream stayed H.264 and unchanged, the sound was AAC and the length was what the rule says. To mix the new sound with the old one, use a video editor. We checked the ffmpeg commands this tool builds by running them with a real ffmpeg on test clips and measuring the results (sizes with ffprobe, picture content with ImageMagick, sound with a spectrum and loudness meter), and the page itself in a browser with the real ffmpeg.wasm engine. The first use downloads the ffmpeg engine (about 25 MB), which then stays in your browser cache. It needs a current desktop Chrome, Edge or Firefox; large videos use a lot of memory, and very long clips can fail on small devices. Your file is processed in your browser with ffmpeg and never uploaded.

How to use it

1. Choose the video.
2. Choose the new sound.
3. Choose how long the result should be.
4. Press Process and download.

Common problems

The video has no sound left from before

This tool replaces the sound. To keep the old sound too, mix both in a video editor.

The sound is out of step with the picture

The new sound starts at the beginning of the video. Trim it with the audio trimmer first to make it start at the right moment.

The result is longer than I wanted

Choose Same as the video, or trim the video first.