AMV format is the video format used by the video enabled S1mp3s.
Files of this format are suffixed with ".amv”.
The container format used by AMV files is a modified version of the AVI format.
It has the strings “AVI” and “avih” in the header replaced with “AMV” and “amvh”. The section where codec, frame size, and other information would normally be found is filled with zeroes (because most of that information is hard-coded into the player). The the string “AMV_END_" is found at the end of the file.
There is a big possibility that the AMV movie format used by S1mp3 is a rip of 'Apex Media Video' for Nintendo Game Boy (Color). Older info on it can be found at the Apex Designs page
Apex claim pretty good compression ratios and it is capable of being decoded on GB. It is possible that AMV is a rip-off of that codec, mainly considering both devices work with a Z80-based instruction set.
The company haven’t replied to the email sent about the issue.
AMV Video format isn’t Apex Media Video format, it is simple motion jpeg where each frame is saved as jpeg.
Here is a simple test to understand what’s in the AMV video file.
make an AVI video of total 10 frames using RAW DATA format, at 12fps sized 160x120 without sound
save eche frame to BMP (do not use jpeg now, name them as 01.bmp ~ 10.bmp)
convert the BMP files to JPEG, be careful with the JPEG compress level
convert the AVI file to 160x120, 12fps AMV, again be careful about the Image quality setting which is the JPEG compress level, and set Image Zoom to 0
compare the AMV and JPEG files using a hex editor
You will find jpeg headers inside the AMV file.
Acoording to a comment in a blog post, AMV and MTV are both AVI based (ffmpeg demuxer has proven to be able to handle it, with a few hacks), some chunks are removed, some are modified. The audio stream is MP3 and the video stream is mostly 160xY MPEG4.
Hope this Helps!