The first version of the codec was used in the games "Blown Away" (1994) and "Panic in the Park" (1995) and has the FourCC code "ipma".
The official name is "Imagination Pilots Transparent AVI Driver [ipma]" as shown in the Windows 95 Multimedia Device Manager.
As seen in VirtualDub, the first frame is the background of the video, and the rest of the frames are a video which has a green background. I do not know how the transparent color is exactly determined.
Before the codec was renamed to "ipma.drv", the original filename is stated as "lzwcodec.drv" . Since the game also uses LZW for its graphics files, it is likely that the video codec also utilises LZW.
In VirtualDub, following information are displayed for this codec:
Name: Imagination Pilots Matte Compressor
Delta frames: Yes
FOURCC code: 'ipma'
Driver name: IPMA.DRV
About dialog: "IP-MATTE, Imagination Pilots Matte Compressor"
Configuration dialog: Imagination Pilots Transparent AVI Driver, Copyright (C) Imagination Pilots 1994, Version "1.10
IPMA.DRV is probably only a decompressor. VirtualDub is not able to encode videos using IPMA.
"IP-MATTE" appears in the "Details" page of an AVI file in Windows 95.
File "IPMA.DRV" has modification date 26. September 1994
Vague mechanism: The first frame contains the background. The other frames contain the transparent video which is placed on top of the background.
The second version of the codec was used in the games "Where's Waldo? At the Circus" (1995) and "Where's Waldo? Exploring Geography" (1996) and has the FourCC code "IP20".
16 Bit codec
Its name is "Imagination Pilots Matte Compressor Ver 2"
The version is still 1.10 and the copyright year still 1994. These things were probably missed during update.
File "IP20.DRV" has modification date 16. March 1995
Vague mechanism: The first frame is not interpreted as background. Instead, the whole video is pure transparent. (You can see the difference between IPMA and IP20 by changing the FourCC code of an AVI file using an hex editor and see the result. Beside the first background frame, the video data is compatible)