Silent clips, screen recordings with a noisy room in the background and holiday footage full of wind often look better with a sound track of your choosing. A voice-over turns a series of shots into an explanation; a piece of music turns it into a mood.
Load a video, choose an audio track, and decide whether the track replaces the video's own sound or plays over it. Set the volumes, choose what happens when the two have different lengths, and press Add audio. The picture is copied without being re-encoded, so the result keeps its original quality and is usually ready quickly.
Replacing versus mixing a sound track
A video file holds the picture and the sound as separate streams. Replace builds a new file from the video's picture stream and your track, leaving the old sound out entirely; it suits music videos, silent clips and narrations that should not compete with background noise. Mix keeps the original sound and plays the track on top of it, each with its own volume, which suits background music under people talking or commentary over game sound. Where the two add up to more than full scale, a limiter holds the peaks down so the mix does not distort.
Only the sound is processed. The video stream is copied byte for byte into a file of the same container, so resolution, sharpness and frame rate are untouched and even long clips finish fast. The new sound is encoded as AAC at 192 kbps in MP4, MOV and MKV files, as Vorbis in WebM and as MP3 in AVI.
Ways people use it
Music for a slideshow or montage
Choose Replace, pick the song, and switch on Repeat the track to fill the video if the music is shorter than the footage.
Narrating a screen recording or tutorial
Record your explanation as an audio file, for example with a voice recorder, and add it with Replace so keyboard clicks and room noise disappear.
Background music under speech
With Mix, keep Video sound volume at 100 percent and lower Track volume to around 20 to 30 percent so the music sits quietly behind the voices.
Volumes and lengths
Track volume runs from 0 to 200 percent, where 100 is the file as it is. In Mix mode a second slider, Video sound volume, sets the level of the original sound on the same scale. If the video has no sound of its own, Mix simply adds the track and a note tells you so.
Three length behaviours cover the usual cases. With End when the shorter one ends, switched on at the start, the result stops when either the video or the track runs out, which avoids silent tails and frozen frames. Switching it off keeps the whole video; if the track is shorter, the rest is silent. Repeat the track to fill the video loops the track from the beginning until the video ends, which is the way to cover a long clip with a short piece of music. The work is done in your browser by ffmpeg compiled to WebAssembly, a one-time download of about 31 MB, and both files may be up to 500 MB.
Bu araç nasıl kullanılır
- Drop an MP4, MOV, WebM, MKV or AVI video on the box above, or click Choose a file.
- Click Choose an audio track and pick an MP3, WAV, OGG, M4A, AAC, FLAC or WebM file. Use its preview to check it is the right one.
- Under Sound, choose Replace or Mix, set the volumes, and decide whether to repeat the track or end when the shorter one ends.
- Press Add audio, play the result and download it.
Limitations
- The track always starts at the beginning of the video. To start it later or use only part of it, cut it first with Trim Audio.
- There are no fades or ducking; the volumes stay constant for the whole clip.
- One video and one track per run. To add several songs in a row, join them first with Merge Audio.
- Only the first audio stream of each file is used.