[MPlayer-dev-eng] About PSX Movies

[Mike Melanson]

Hi team,
	Since I've never really played any Playstation games, I spent some
time picking friends' brains and doing Google searches on how the CDs and
movies work. Here's some stuff I've come up with:

* PSX games use the CD-ROM XA format, which was developed to be conducive
for multimedia applications. Apparently, the format has something to do
with interleaving sectors of data from different file (say, audio and
video files). I guess this was the hardware solution to the problem of
keeping multimedia streams (video, audio, and text) in sync without
seeking everywhere (hey, ever hear of interleaved file formats,
like AVI, MOV, FILM, RM, etc.?...:). So that's why you need to have custom 
ripping software to extract the data properly. I hear that most OS's will
recognize the CD as a regular CD-ROM with an ISO-9660 fs, but if you try
to copy the data directly, things are likely to get jumbled.

* The PSX has a hardware module that some refer to as the motion decoder.
This module takes 16x16 macroblocks of data encoded with DCT/0-RLE and
decompresses them. It's capable of processing 9000 macroblocks/second.
Since a 320x240 image is comprised of 300 macroblocks, the motion decoder
has a theoretical max throughput of 30fps and full 320x240 resolution. But
I hear that many PSX movies are only 15fps.

* Many PSX games have movies stored in a .STR (stream) format. They're
comprised of blocks that are designed to be shuttled directly to the
motion decoder via DMA.

* Audio is a different story, apparently. It's not interleaved in the STR
file. I hear that sometimes a CD audio track is played and sometimes
there's a custom MIDI-style song playing on the PSX audio facilities.
Apparently, the PSX also has some ADPCM facilities (in which case, I wager
that the ADPCM format would look the same as for the Super Nintendo's
SPC-700 chip, since Sony made that too).

Rick <rick at topaz.ne.mediaone.net>: I would appreciate if you could upload
to the MPlayer FTP a small-ish STR file that has been properly ripped from
a PSX game (small-ish means try to keep it under about 10MB).
Alternatively, you could give me the titles of some PSX games that are
known to have good STR movies, and that I could find at a used game shop
for < $10.

	Thanks...
--
	-Mike Melanson