ffmpeg dev podcast

How to Convert MP3 to MP4 with FFmpeg

By Frizky
· ·
6 min read
Video editing timeline with video and audio tracks on a dark screen

You have an MP3. Maybe a podcast episode, maybe a song. And you want it on YouTube or Instagram.

Problem is, those sites want video. Not audio.

The fix is simple. Put a still image on top of your audio and save it as an MP4. FFmpeg can do this in one line. I'll show you how, and I tested every command in this post myself.

1. Install FFmpeg

FFmpeg is free. Pick the one for your computer:

  • Mac: brew install ffmpeg (you need Homebrew for this)
  • Windows: winget install Gyan.FFmpeg
  • Linux: sudo apt install ffmpeg

No package manager? Download it from the official website.

To check, run ffmpeg -version. If you see a version number, you're set.

2. The basic command

Put your MP3 and your image in one folder. I'll call them audio.mp3 and cover.jpg. Open your terminal in that folder and run this:

ffmpeg -loop 1 -i cover.jpg -i audio.mp3 -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M output.mp4

Terminal showing the FFmpeg command and the new output.mp4 file

Done. You now have output.mp4.

Looks long, right? Don't worry, it's not as scary as it looks:

  • -loop 1 -i cover.jpg shows your image over and over, once for every frame.
  • -i audio.mp3 is your sound.
  • -c:v libx264 makes H.264 video. YouTube, Instagram and TikTok all take it.
  • -tune stillimage lets FFmpeg know nothing moves, so the file stays small.
  • -c:a aac -b:a 192k saves the audio as AAC. 192 kbps sounds great for voice and music.
  • -pix_fmt yuv420p is the boring one you still need. Leave it out and QuickTime shows a black screen.
  • -shortest -fflags +shortest -max_interleave_delta 100M stops the video when the audio ends. More on this one below.
  • output.mp4 is the name of your new video.

3. Why is my video longer than my audio?

This one got me.

Most guides online only use -shortest. So I tried that first. My audio was 8.5 seconds long. The video? 25 seconds. The last part was just the image with no sound.

The looped image runs ahead of the audio, and -shortest alone doesn't catch it in time. Adding -fflags +shortest -max_interleave_delta 100M fixed it for me. The video came out at 8.56 seconds.

So if your video has a long silent tail, that's the reason. Use the full command from step 2.

4. Pick the right size

The basic command keeps the size of your image. A square cover gives you a square video. That's fine for some places. But each platform has its own favorite size.

YouTube (16:9)

ffmpeg -loop 1 -i cover.jpg -i audio.mp3 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M youtube.mp4

This puts your image in the middle of a 1920x1080 frame, with black bars on the sides. Like this:

Square podcast cover centered in a 16:9 video with black bars

Want to upload it as a podcast? Here's my guide on how to upload your podcast to YouTube.

Instagram Reels and TikTok (9:16)

Same trick, just a tall frame:

ffmpeg -loop 1 -i cover.jpg -i audio.mp3 -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2" -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M reel.mp4

Instagram feed (1:1)

Got a square cover? Just scale it to 1080x1080:

ffmpeg -loop 1 -i cover.jpg -i audio.mp3 -vf "scale=1080:1080" -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M square.mp4

Not sure which size to use? I wrote a whole post on how to post audio on Instagram.

5. Add a waveform

A still image is a bit boring. People scroll right past it. A moving waveform shows that something is playing.

FFmpeg has a filter for that called showwaves:

ffmpeg -loop 1 -i cover.jpg -i audio.mp3 -filter_complex "[1:a]showwaves=s=1200x240:mode=cline:colors=white[wave];[0:v][wave]overlay=(W-w)/2:H-h-80:shortest=1[v]" -map "[v]" -map 1:a -c:v libx264 -c:a aac -b:a 192k -pix_fmt yuv420p -shortest waveform.mp4

Here's a frame from my test video:

Podcast cover with a white audio waveform at the bottom

A few things you can change:

  • s=1200x240 is the size of the waveform.
  • mode=cline is the style. Try line, p2p or point too.
  • colors=white is the color. Any color name or hex code works, like 0x1b00ff.
  • H-h-80 places it 80 pixels from the bottom.

Note the shortest=1 at the end of the overlay. It does the same job as the flags in step 3, so the video stops when the audio does.

Want more control over the look? My post on audio waveform animations goes deeper.

6. Convert a whole folder at once

Got a bunch of episodes? Run this and grab a coffee. Every MP3 in the folder gets its own MP4, all with the same cover:

for f in *.mp3; do ffmpeg -loop 1 -i cover.jpg -i "$f" -c:v libx264 -tune stillimage -c:a aac -b:a 192k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M "${f%.mp3}.mp4"; done

So episode-1.mp3 turns into episode-1.mp4. Spaces in file names are fine too. This one is for Mac and Linux. On Windows, run it in Git Bash or WSL.

Don't like the command line?

I get it. FFmpeg is great, but it's a lot of typing for one video. And it can't easily do subtitles, progress bars or nice templates.

That's why I built Vokal. You upload your MP3, pick a template and add a waveform, subtitles and your logo. Then export. No commands needed.

Try it for free. No credit card needed.

More FFmpeg guides from me:

Frequently asked questions

Sort of. A video needs pictures, but they can be plain black. Swap -loop 1 -i cover.jpg for -f lavfi -i color=c=black:s=1920x1080 and you're done.

Wrapping up

That's really all there is to it. One command, one image, one MP3. Pick your size, maybe add a waveform, and you're ready to post.

Happy converting!

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