M4A to MP4, sound with a picture.

An M4A file holds sound only, and an MP4 is a video, so turning one into the other means giving the sound a picture. That is what this page does. You choose a cover picture or a plain colour, and optionally a waveform that moves with the sound, and it saves an MP4 as long as the sound, with H.264 picture and AAC sound. The sound is saved as AAC, and you can tick a box to copy an M4A's AAC across as it is. Any other sound file works too. Nothing is uploaded, there is no sign-up and there is no watermark.

How to convert M4A to MP4

1. Drop an M4A, MP3, WAV, OGG, FLAC or AAC file on the box, or click to choose. A video file works too, and its sound is used.
2. The preview shows at once. Press Play, or Space, to hear the sound with the picture, and drag the bar to go to another place.
3. Press Choose a picture to add album art, a logo or a photo. With a picture, pick Whole picture to show all of it, or Fill the frame to crop it to fit. Without one, pick a Background colour.
4. Under Moving waveform, choose Bars or Line if you want the picture to move with the sound, and a colour for it.
5. Pick the shape and the size: Wide 16:9, Square 1:1 or Tall 9:16, at 1080p or 720p, smaller.
6. Press Make the MP4. When it is ready, play it on the page and press Download the MP4. Change the picture or look goes back to the settings.

Why a video site wants an MP4

A site for video expects a video file. An M4A has no picture, so the site has nothing to show. YouTube's page on recommended upload settings, checked 18 Oct 2026, lists MP4 as the container, H.264 as the video codec and AAC-LC or Opus as the audio codec, with 48 kHz sound. It says 16:9 is the standard shape on a computer and that vertical and square videos are accepted. It also asks for the moov atom at the front of the file, which this page does, and lists "No Edit Lists" as a recommended setting. An M4A usually carries one edit list to hide the start-up delay of its AAC sound, and copying the sound would carry it into the MP4. So the sound is saved again as AAC by default, which writes none. Read the page at support.google.com/youtube/answer/1722171. If you want the original sound bytes, for example for an archive, tick Copy the sound as it is, without saving it again.

Picture or waveform

A still picture is saved as a slow video, two frames a second, or one frame a second for sound longer than half an hour. That keeps the file small, because a picture that does not change adds almost nothing to the size, and the last frame runs to the exact end of the sound, so the video is as long as the sound. A moving waveform runs at 30 frames a second. Its bars are worked out from the sound itself, a small piece at a time, so the preview and the saved video match. Moving video takes longer to make: a still picture of a ten minute sound takes only a few seconds, while a waveform has to draw 18,000 frames, since 10 minutes is 600 seconds and 600 times 30 is 18,000.

Sizes

The sound takes most of the space in a still picture video. At 128 kbps, ten minutes of sound is 128,000 bits a second times 600 seconds, divided by 8, which is 9.6 MB, and the picture adds little to that.

Common problems

• "That file has no sound in it." The file is not sound, or a video with no sound track. Choose another file.
• The browser cannot make H.264 or AAC. Use a current Chrome, Edge or Safari.
• The picture will not open. Use a JPG, PNG or WebP. Some browsers cannot open HEIC pictures.
• A long sound with a waveform is slow. Switch the waveform off, or pick 720p. A still picture is much quicker.
• Renaming does not work. Changing the ending from .m4a to .mp4 does not add a picture. Many sites check for a video track and reject the file.

To trim the sound first, use the audio cutter. For short clips with a title and a cover for social media, try the audiogram maker.