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Old 05 April 2012, 17:30   #1
Mad-Matt
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Was CDXL format Optimal for CD32

Just a passing thaught really. Was CDXL Optimal for the CD32 or could a better codec have been developed for fullscreen fmv sequencies. Could we of had games such as Rebal Assault or any number of fmv games that were doing the round in 94,95.

I've been Longplaying alot of SegaCD games recently, and you can see the progress from its earlier games, Small grainy window to the later games full screen video (around 288x230) with 10-15 fps playback which was just enough not too luck juddery.

Would it have been commodores job to continue refining there own codec or could devs have done this on there own if they wanted too. Given that they prefured to just stick floppy versions of gameson a cd with no extras I dont know if they would have bothered even though fmv footage existed from their sega/pc games.
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Old 06 April 2012, 01:01   #2
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Those Sega CD videos were limited to 16 colours I'm pretty sure. You could make a 16 colour CDXL almost full screen and have it playing at the same speed on a CDTV or CD32 too. The reason so many CDXLs are a lot smaller than Sega CD videos is because they're spooling 4,096 colours per frame. You can make and play CDXLs in any Amiga colour depth except 18bit, so with a bit of playing around you could maybe get a full screen video playing at a decent framerate at around 16-32 colours. I've always wanted to experiment with converting a Simpsons episode or something. You can also use the Copper to double the height of a CDXL video. I've made example CDXLs using 4,096 and 256 colours which are 320x80, and are played at 320x160 making them roughly the same aspect ratio as a widescreen movie, and they fill the screen (apart from overscan areas). I've tested them on a real CD32 and they play fine, and I calculated you could fit around 45 minutes of video on a CD if you used this format. So an hour and a half long film could be divided onto two CDs similar to a Video CD, but would be playable on all CD32s, but the film would have to be in 2.35:1 roughly to start with unless you want to crop or shrink the video... or reduce the colours to less than 256.

A colour-mapped CDXL can use a different palette for each frame, so you might get nice results from 128 colours using a good image processing program to convert all the frames with a smart colour-reduction and dithering routine.

I don't know if the 68EC020 would be fast enough to deal with any kind of compression for a streaming video either, but it would be interesting to know if the frames or audio could be compressed slightly if a new format was created.
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Old 06 April 2012, 04:53   #3
Minuous
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I'm not aware of any Amiga that supports 18-bit screenmodes. 15, 16 and/or 24 bits, yes, but not 18 bits.
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Old 06 April 2012, 12:27   #4
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HAM8 was always described as a pseudo 18bit mode. But it was 8bit, but had a 24bit palette...so who knows what it was! I always thought of it as a 24bit mode with colour placement difficulties...

It would be interesting to know if CDXL was optimal, I guess 030's and above could of handled additional compression.

Also were the CDXL limitations (colours/resolution) on the CD32 due to drive speed/640MB limit, or was it more to do with the processor being at it's limit?
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Old 06 April 2012, 16:13   #5
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Microcosm seems to be a good cadidate for quality comparison between cd32 and Sega cd. Whatever codec/compression sega used its clearly of lower quality then cd32 version. However the cd32 version does seem to use much smaller footage even though its overall clearer. I do recall a button combo to get the cd32 intro full screnn, but it didnt look too good.

CD32 was suposably the most popular cd console before playstation/saturn so I do wonder what stopped em using cd32 for its fmv capabilities for those kind of games. Not saying they were good games, but the cd32 seemed to be ignored as sega pc and 3d0 were getting the fmv games and nobody had a 3d0. Even when commodore went bust, cd32 was still outthere in more holmes then segacd and deffinatly 3d0.

Which brings me back to, would cdxl have been good enough for a fullscreen fmv game. Microcsom shows it could work, and have liked to see that Rebal Assault on cd32 and maybe even Psygnosis's Novastorm.
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Old 06 April 2012, 19:28   #6
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Quote:
Originally Posted by Minuous View Post
I'm not aware of any Amiga that supports 18-bit screenmodes. 15, 16 and/or 24 bits, yes, but not 18 bits.
A1200, A4000 and CD32 support it, it's called HAM8 and displays 262,144 colours on screen from a 24bit palette.


As for the CDXL limitations on the CD32 it was the 2x speed CD drive holding back the size and quality of the video, which is why CDTV CDXLs are half the size of CD32 ones, they were designed to spool from its 1x speed CD drive.

The reason the CD32 missed out on a lot of the FMV games is because it was never officially released in USA where most of those games were made and became popular. Nearly all the CD32 games ended up being from smaller European development houses.

Last edited by Rebel-CD32; 06 April 2012 at 19:34.
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Old 06 April 2012, 20:29   #7
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Was the microcosm intro even CDXL?

Reason I ask is WinUAE has always played it reasonably well and other intros I know to be CDXL stutter throughout, and the quality is far higher than others too.
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Old 07 April 2012, 00:56   #8
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Quote:
Originally Posted by Rebel-CD32 View Post
A1200, A4000 and CD32 support it, it's called HAM8 and displays 262,144 colours on screen from a 24bit palette.
Yes, I know what HAM8 is, however 262,144 is an arbitrary number which doesn't accurately describe the actual number of colours possible in this mode. You can have more colours than that, subject to resolution of course.
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Old 07 April 2012, 10:14   #9
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in my opinion most of these systems shouldnt have used fmv to begin with. Very low quality, combined with poor low budget cg or worse bad acting.

Many of the old floppy intros look alot more appealing than the fmv ones.
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Old 18 June 2016, 05:23   #10
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Originally Posted by Rebel-CD32 View Post
You can also use the Copper to double the height of a CDXL video. I've made example CDXLs using 4,096 and 256 colours which are 320x80, and are played at 320x160 making them roughly the same aspect ratio as a widescreen movie, and they fill the screen (apart from overscan areas).
How to do that? Any chance of example how and where to call copper for double the height of CDXL video?
 
Old 18 June 2016, 07:33   #11
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You would need to change the modulo on each scanline.
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Old 18 June 2016, 09:04   #12
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You would need to change the modulo on each scanline.
No its only a simple command in the cdxl startup sequence 'sdbl' i think it is.
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