Better VMD Support in NihAV

As the certain doctor from ScummVMTrek reminded me, the VMD format (developed by Coktel Vision that was bought by Sierra) was used in their own games too (and even more so, there VMDs were used for many animations where simple sprite would suffice as well) and they kept making some educational games way into 2000s. So I decided to look at those as well.

The Last Dynasty (which I’ve never played and unlikely to ever play) features VMD that can be decoded mostly fine except that in 320×161 video you sometimes have sudden 640×322 frames near the end of video.

Some education game from Adi 4.0 generation. This one has some videos in 15-bit RGB format plus IMA ADPCM compressed audio track. But it can’t beat the weirdness of…

Urban Runner. Here we have a mix for 15-bit RGB VMD, 24-bit RGB VMD and VMDs with Indeo 3 video. And if you thought this was simple enough here’s another fun trick for you. Despite having different depths, all non-Indeo3 VMDs use the same compression methods, just in some cases the buffer should be interpreted as bytes, sometimes as 16-bit little-endian words and sometimes like triplets. So far so good. But they had a bright idea of sometimes storing the image dimensions in pixels and sometimes in bytes. In result I look at VMD header to see what flavour it has there to see if I need to scale frame dimensions by bytes per pixel before decoding or not. And this game also features some videos that have 312×136 resolution except that the last frame is 624×272 (I had to allow my Indeo 3 decoder to change dimensions to handle that particular case).

At least it could be done mostly by guesswork (except for audio, I had to look into ADI4.exe using Ghidra to find out that it has IMA ADPCM now) and all files can be decoded fine now.

If somebody can provide me with some samples and binary for their latest generation I’d look at it as well.

One Response to “Better VMD Support in NihAV”

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