# MP3 to MP4 converter: add a picture to audio, free, no upload

> Turn an MP3 or other audio into an MP4 video with a still picture, in 16:9 for YouTube, 1:1 or 9:16. The sound is encoded to AAC and nothing is uploaded.

URL: https://cutfac.com/tools/mp3-to-mp4  
Last updated: 2026-10-28  
Language: [한국어](https://cutfac.com/ko/tools/mp3-to-mp4)

Drop in an MP3 and a picture, such as cover art, and get an MP4 video to upload where audio files aren't taken. Everything happens in your browser.

Runs in your browser. Nothing is uploaded.

## How to use it

1. **Add the audio.** An MP3, M4A, WAV or any audio your browser plays.
2. **Add a picture and pick the shape.** Cover art or a photo, fitted inside the frame. 16:9 for YouTube, 9:16 for Shorts and Reels.
3. **Make the MP4 and download.** Play it to check the sound, then download it.

## Why turn audio into a video

Video sites and apps take video files, so a song, a podcast episode or a voice-over needs a picture to go up. The MP4 shows the picture for the whole length of the sound.

The picture is fitted inside the frame without cropping. A square cover in a 16:9 frame gets black bars at the sides; a photo of the frame's shape fills it.

## What's inside the MP4

The picture is encoded as H.264 at one frame a second, which is all a still picture needs and keeps the video track tiny. Most of the file is the sound: up to about 1.4 MB a minute.

The sound is encoded to AAC at 192 kbps. YouTube's formatting specifications ask for AAC at 128 kbps or better in an MP4, so it's above that.

## With ffmpeg

The same video on the command line. -tune stillimage tells the H.264 encoder the picture doesn't move:

- ffmpeg -loop 1 -framerate 1 -i cover.jpg -i song.mp3 -c:v libx264 -tune stillimage -pix_fmt yuv420p -c:a aac -b:a 192k -shortest song.mp4

## Sources

- [YouTube Help: Video and audio formatting specifications](https://support.google.com/youtube/answer/4603579)
- [FFmpeg Wiki: H.264 video encoding guide](https://trac.ffmpeg.org/wiki/Encode/H.264)

## Questions

### Is my audio uploaded?

No. The sound and the picture are encoded into the MP4 in your browser. Nothing is sent anywhere.

### Do I need a picture?

No. Without one the video is black, with the sound as it is.

### Which shape should I pick?

16:9 for a regular YouTube video, 9:16 for Shorts, Reels and TikTok, 1:1 for a square post.

### Does the sound lose quality?

It's encoded once more, to AAC at 192 kbps, which keeps music close to a typical MP3. Video sites encode it again after upload anyway.

### How long can the audio be?

The MP4 is built in your browser's memory, so very long recordings may not fit. An hour comes to about 90 MB, which most computers handle.