Free tool
Free MP3 to MP4 converter with a waveform or image
Turn an MP3 into an MP4 video so you can post it where only video is accepted: YouTube, LinkedIn, Instagram, an LMS or a slide deck.
Your audio
Drag a file here, paste it, or choose one.
.mp3, .wav, .m4a, .aac, .ogg, .oga, .opus, .flac, .aif, .aiff. Up to 500 MB.
Up to 30 minutes with a still background, 15 with a waveform.
Your audio never leaves your browser. The video is made on this machine.
Result
Worked example
Measured on our own 2 minute 17 second narration as MP3, made into a 16:9 MP4 with a waveform.
Source MP3
3.1 MB
MP4, 1280 by 720
28.1 MB
Made in 67 seconds in Chrome on a laptop, including the one time engine download. The moving waveform is most of that size; a still colour or image background makes a file close to the size of the audio.
1. Add your audio. 2. Pick a background and shape. 3. Make the video. 4. Watch and download.
What Interlace does
A waveform is a start. Interlace draws the scenes.
- Paste the episode's script or show notes
- Every point gets its own illustrated scene, narrated
- 16:9, 9:16 or 1:1, with your logo, colours and fonts
Real Interlace output, unedited. Shown silent and sped up.
Your file
podcast-ep-12.mp3
With a waveform, 16:9
Questions
Asked and answered
No. The file is read by the page and converted by ffmpeg compiled to WebAssembly, on your own machine. There is no upload step, and closing the tab discards everything.
Because most places people watch only take video. YouTube, LinkedIn and Instagram need a video file, and many LMS players and slide tools handle MP4 better than MP3. A waveform or a cover image tells people it is audio before they press play.
Video is the slow part, because every frame is encoded in one browser thread. A plain colour or a still image is quickest. The waveform redraws every frame, so it takes longer: in the worked example, 2 minutes 17 seconds with a waveform took 67 seconds on a laptop, including the first download of the video engine.
16:9 for YouTube, LinkedIn and an LMS. 9:16 for Reels, Shorts and TikTok. 1:1 for a square post in a feed. An image is fitted inside the frame with your background colour around it, or set to fill the frame with the edges cropped.
Put the title on the image before you add it. For captions, make an SRT with the SRT and VTT generator, then burn it into the MP4 with the subtitle burner.
30 minutes with a colour or image background, 15 minutes with the waveform. The waveform changes every frame, so its file grows by about 12 MB a minute, and all of it has to fit in the browser tab's memory.
Turn this into a video
Create an account and start from a document, script, or prompt.