Question 1

How do I add music to a silent video?

Accepted Answer

Upload the video and the audio track, choose "replace or add" mode, and merge. The picture is copied untouched, no re-encoding, so quality is identical and the job is fast, while your audio is encoded as standard AAC that every player accepts. If the audio is longer than the video, the merge stops at the end of the video; if it is shorter, the rest of the video stays silent.

Question 2

What is the difference between replace and mix?

Accepted Answer

Replace throws the video's original sound away and uses only your new audio, right for silent clips and for videos whose recorded sound is noise. Mix keeps both: your added track plays together with the original audio, right for adding background music under a voice recording. Mix needs the video to actually have an audio track; for a truly silent video, use replace, which works whether or not the original had sound.

Question 3

Will adding audio reduce my video quality?

Accepted Answer

No. In both modes the video stream is copied bit-for-bit (stream copy), so the picture is exactly the original file's picture. Only the audio is encoded, to AAC at a clean bitrate. This is also why the merge is dramatically faster than a full editor export: the heavy half of the file is never re-processed.

Question 4

Which audio files can I add?

Accepted Answer

MP3, WAV, M4A, AAC, OGG and FLAC all work, as does the audio from another video file if you drop one in. The output is always an MP4 with AAC audio, the most compatible combination for phones, browsers and social platforms. If your video is in a format whose picture cannot live in an MP4 container, the merge will report it rather than silently producing a broken file.

Question 5

My music is longer than the clip. What happens?

Accepted Answer

With replace mode, the output ends when the video ends: the extra music is trimmed automatically (the -shortest behaviour). To loop a short track under a long video or fade it out gracefully, that is an editing-suite job; for the common cases, a soundtrack swap or a music bed under speech, this merge is exactly the tool, and it happens on your device without an upload.

Add Audio to Video

Use Add Audio to Video

How to use the Add Audio to Video

Add the video

Add the audio

Replace or mix

Download the merged MP4

About the Add Audio to Video