Convert AVI to MP4

What is inside an AVI

Microsoft introduced AVI (Audio Video Interleave) in 1992. It is a container, and what it holds depends on what made the file:

• DivX and Xvid: compact MPEG-4 video from the 2000s, often sized at 700 MB a film so it fit on a CD.
• Motion JPEG: what many digital cameras of that time recorded, each frame stored as a separate photo, which makes the files big for their length.
• DV: footage captured from MiniDV camcorders over FireWire, about 13 GB an hour.
• H.264, from some later cameras and screen recorders, which goes into an MP4 untouched.
• Older codecs or no compression at all, from capture cards, webcams and early screen recorders.

Octoolo reads anything FFmpeg reads, so all of them open, whether the sound is MP3, PCM or Dolby Digital. Not sure what a file holds? Add it anyway: its row names the codec before anything is converted.

Copy the Xvid, or make H.264?

Xvid, and DivX from version 4 on, are MPEG-4 video, which an MP4 may hold. With As it is, Octoolo copies them across together with MP3 sound: instant, and not a pixel changes. The catch is that this older kind of MPEG-4 plays in VLC and on many PCs, but browsers such as Chrome and Edge do not play it, and many phones and TVs expect H.264.

So for files you will share, upload or watch on a phone, choose High: the picture becomes H.264 and the sound AAC. Whatever cannot be copied is converted to H.264 with either setting: DivX 3, Motion JPEG, DV and uncompressed video, with PCM sound becoming AAC. A quick way to tell: rows marked MPEG-4 or H.264 can be copied, everything else will be converted.

What happens to the size

Motion JPEG camera clips and DV captures shrink the most. H.264 needs only a small part of the data those formats use, so the MP4 often ends up a small fraction of the AVI's size, made at high quality. An hour of DV, about 13 GB, comes out at roughly a gigabyte. Xvid copied with As it is keeps its size; converted at High it usually gets somewhat smaller, since High never spends more than the original needs.

Octoolo never enlarges a picture. Under More settings, Size keeps 640 × 480 or 720 × 576 as it is and lets you pick only smaller sizes. Old video stretched to HD gains no detail anyway.

Tips for a big archive

Drop the top folder of the archive: Octoolo finds up to 500 videos, three folders down, in name order. Under Save in, A folder I choose… collects every MP4 in one place; otherwise each lands beside its AVI. When an AVI sits somewhere Octoolo cannot write, such as an old CD, its MP4 goes to an Octoolo folder in Videos and the row says where.

Up to four conversions run at once, but only one re-encodes a picture at a time, so quick copies keep moving while a long DV capture is being converted. A file that FFmpeg cannot read shows why in its row and is skipped, and the rest go ahead. Need the PC back? Stop all halts the batch, and finished MP4s stay. Your AVIs are never changed: check the MP4s before deleting anything.