[MPlayer-dev-eng] About PSX Movies

[D Richard Felker III]

On Tue, Feb 12, 2002 at 09:01:59AM -0700, Mike Melanson wrote:
> 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 

the other purpose is that you get more storage space (maybe 10-15%
more) at the expense of easy seekability and of reliable error
correction when the cd is scratched.

> 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.

thats because the sectors containing the data for the movie files
extend outside the normal mode1 (2048 byte) sector boundaries, into
the space normally used for format header information.

> * 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.

this is correct -- in fact most are only 15 fps afaik.

anyway, i don't know all that much about psx stuff myself, but i know
a few people who do, so if any big questions come up let me know and i
might be able to get some info.


rich