AVI to MP4 Converter

AVI is Microsoft's old video container. Files from the DivX and Xvid era, early digital cameras (Motion JPEG), DV camcorders and screen recorders still turn up as AVI, and phones, browsers, smart TVs and upload sites often refuse them. This converter turns them into H.264 MP4 with AAC sound inside your browser, keeping MP3 and AAC sound as it is and deinterlacing camcorder video. The video engine (ffmpeg, about 30 MB) downloads the first time, and your files are never uploaded.

How to use this tool

1. Choose the options first: quality, deinterlacing and maximum resolution.
2. Choose one or more .avi files; conversion starts right away.
3. Watch the progress bar — re-encoding runs at about 27 frames per second for 480p and 12–13 for 720p on a recent computer.
4. Play the MP4 in the page and download it (several files come as one ZIP).

Formula

Output = H.264 video (x264, CRF 18–26) + audio (MP3/AAC copied, other formats → AAC 160 kbps) in an MP4

CRF is a constant-quality setting: lower numbers mean better pictures and bigger files, and every 6 steps roughly halves or doubles the size. MP3 and AAC sound is copied unchanged; PCM, ADPCM, MP2 and AC-3 sound is converted to AAC, the format MP4 players expect. Deinterlacing uses the yadif filter, which turns each pair of fields into a smooth progressive frame. The picture is always re-encoded, even when the AVI holds H.264: AVI stores frames in decoding order without display times, and copying them into an MP4 would make B-frames play out of order.

Example

A 12-minute Xvid AVI at 640 × 352 and 25 fps has 18,000 frames. At about 27 frames per second (480p-class speed) the conversion takes roughly 11 minutes and gives an MP4 of similar or smaller size at CRF 22. Choosing 480p as the maximum keeps that speed for larger sources too.

DV camcorder tapes

Footage captured from MiniDV tapes is interlaced and uses non-square pixels (720 × 576 for PAL, 720 × 480 for NTSC, shown as 4:3 or 16:9). "Automatic" always deinterlaces DV, and any other file marked as interlaced, and the pixel shape is stored in the MP4, so players show the correct width. Choose "Always" for an MPEG-4 or Motion JPEG capture that shows comb lines but is not marked.