How to use the AVI to MP4 converter
- Choose the AVI files, DivX and Xvid ones included.
- Pick a quality. High holds on to the most detail from low-resolution tapes and captures.
- Convert, then download each MP4 or all of them together.
Why the MP4 shrinks
DivX and Xvid (MPEG-4 Part 2) and MJPEG need far more bits than H.264 for the same picture. At Balanced, a typical home-video AVI comes out at half its size or less with no visible difference.
MP3 or uncompressed PCM soundtracks become 160 kbps AAC, which is what MP4 players expect to find.
Where the work happens
Browsers cannot read AVI by themselves, so ffmpeg compiled to WebAssembly does the decoding and encoding. Your first conversion fetches that engine, roughly 31 MB, and later ones reuse the cached copy.
The engine works on a single core: SD clips finish quicker than they play, a 1080p AVI takes longer than its running time. Interlaced camcorder material is converted as it is, without deinterlacing.
Odd frame sizes
Some capture cards produced AVIs with odd dimensions or non-square pixels. Because H.264 wants width and height divisible by two, one line of pixels may be shaved off, and the original pixel shape is preserved so faces are not stretched.
When you only want the sound from an old clip, Video to MP3 is far quicker than converting the whole picture.
Questions
The converted clip is silent. Why?
First check that the AVI plays with sound elsewhere. Unusual audio codecs are decoded by ffmpeg too; an error in the queue usually means a damaged file.
Can I queue lots of AVIs?
Yes. They are processed one after another and the ZIP button collects every MP4.
Should I pick High or Balanced?
High for small or low-resolution AVIs, where every detail counts. Balanced is fine for most clips and gives a lighter MP4.
Is anything uploaded?
No. The ffmpeg engine runs inside your browser, so family videos never leave your computer.