AVI to MP4 Converter

AVI is one of the oldest video formats still in circulation. Microsoft introduced it in 1992, and for more than a decade it was the default for camcorder transfers, early digital cameras, screen capture tools and video downloads encoded with DivX or Xvid. Hard drives and old DVDs are full of these files.

The format itself is simple: it interleaves chunks of audio and video in one file. What goes into those chunks varies widely, and that is the problem. A clip from a 2005 camera may use Motion JPEG, a downloaded film may use DivX or Xvid, and a capture card may have used a codec that no longer exists. Current phones, smart TVs and browsers do not ship decoders for most of them, so the file opens with no picture, no sound or an error.

Converting decodes whatever codec the AVI uses and writes H.264 video and AAC audio into an MP4 container. That combination is supported by practically every device sold in the last fifteen years.

Expect a big drop in file size for camera footage. Motion JPEG compresses every frame as a separate picture, while H.264 reuses what stays the same from frame to frame. A clip that filled a memory card in 2006 often becomes an MP4 of a fraction of the size, with no visible difference.

Resolution, frame rate and aspect ratio are kept as they are. Old standard-definition clips stay standard definition, and 4:3 video keeps its shape rather than being stretched to fill a widescreen TV.

Because the old codec only has to be decoded once, the MP4 no longer depends on it. You can delete codec packs you installed years ago just to watch these files, and the MP4 will still play.

Watch one converted file from start to finish before you convert a whole collection. Look at fast movement, where old codecs and low bitrates show blocky patches; those were already in the AVI and will look the same in the MP4. Listen for sound that drifts out of sync toward the end, which can happen with AVI files that were written by unreliable capture software.

If one clip in a series fails while the others work, the file itself is often damaged, for example by an interrupted copy from a camera card. Try copying it again from the original medium if you still have it. Files that play from start to finish in any player on your computer usually convert without trouble.

Keep the MP4s and the AVI originals in separate folders. That way you can share or edit the MP4s freely and still go back to the source if a better tool or a new format comes along.

Old camcorder transfers are often split into many short files. Add up to 20 at a time, each up to 95 MB, and download the MP4s together. Files larger than that can be trimmed into parts with Trim Video first. Uploaded files are removed after processing and the MP4s 30 minutes later.

Name the files by date before you convert, because the names carry over to the MP4s and make an archive much easier to browse. For other targets, such as MOV for an Apple editor or a smaller file for email, the Video Converter and the Compress Video tool take the same batches.