.AVI is not a format, it’s a container.
“An AVI file may carry audio/visual data inside the chunks in virtually any compression scheme, including Full Frame (Uncompressed), Intel Real Time (Indeo), Cinepak, Motion JPEG, Editable MPEG, VDOWave, ClearVideo / RealVideo, QPEG, and MPEG-4 Video.”
As nwgat suggests, use mediainfo to identify which encoder has been used for your source.
► MediaInfo - Download