What you should know
AVI (Audio Video Interleave) is Microsoft's video container, introduced with Windows 3.1 in 1992. For two decades it was the de facto standard for home videos and early DivX files.
Its simple structure, inherited from RIFF files, explains its longevity: it accepts almost any codec, which makes it unpredictable but always open.
Strengths
- Readable by an enormous variety of players, including old ones
- Very common in personal archives and digitised video
- Simple, well-documented, royalty-free container
- Accepts many codecs, from MPEG-4 to MJPEG
Limitations to know
- No native support for multiple tracks or modern subtitles
- No progressive playback: an AVI often plays only after a full download
- Larger files than MP4 at equivalent quality
- The lack of a codec standard makes compatibility unpredictable from one file to the next
When to use it
Convert an AVI when you need to play it on a recent device, publish it or send it: MP4 is then the natural choice. Keep the original AVI as an archive only if you do not need to edit it.
Quality, size and compatibility
An old AVI often contains a dated codec — DivX, Xvid, MPEG-4 Part 2 — that must be fully re-encoded. Quality then depends on the output bitrate: since the source is already compressed, avoid aiming too low or artefacts will show.
Frequently asked questions
- Why is my AVI so large?
- The AVI container and older codecs compress less efficiently than H.264. Converting to MP4 can cut the size sharply at comparable visual quality.
- Do all AVI files convert?
- Almost all. The hard cases are AVI files with very old or exotic codecs: FFmpeg often decodes them, but output quality remains limited by the source.