When AVI is the right target
AVI is one of the oldest video formats still in use. It is simple, and for that reason a lot of older software and hardware supports it and nothing newer. People usually convert 3GP to AVI for one of these reasons:
- An older video editor, such as Windows Movie Maker or VirtualDub, cannot import 3GP but accepts AVI.
- A DVD player, a car screen or a digital photo frame plays AVI from a USB stick but shows an error for 3GP.
- Software for motion analysis, sports coaching or science projects needs AVI input.
If none of this applies to you, MP4 is a better choice: smaller files and support on every modern device. See 3GP to MP4.
What the converter does
A 3GP file from a phone usually contains H.263 or MPEG-4 Part 2 video and AMR speech audio. These are not suitable for AVI players, so both streams are decoded and encoded again with codecs that AVI players commonly read. The work is done by the built-in converter engine, which runs inside your browser. It needs no installation and never sends your files to a server.
Fixed frame rate matters for AVI
AVI files store a fixed number of frames per second. Phone videos, on the other hand, were often recorded with a frame rate that changed with the light, for example dropping to 7 or 10 fps indoors. When such a clip is converted, the tool needs a fixed rate. Choose 15 fps to stay close to the original, or 25 or 30 fps if the AVI will be used in an editor together with other footage. This avoids sound that slowly drifts away from the picture.
About file size
AVI codecs are less efficient than those in modern MP4 files, so the AVI may be several times larger than the 3GP. With old phone footage this usually still means only a few megabytes per minute. If it matters, lower the quality preset, or use the AVI Compressor afterwards. To convert AVI videos back for an old phone, open AVI to 3GP.