The astonishing unpopularity of "dynamic-highres"

[ChaosLord]

@mr_a500

Use jpeg quality setting of 100% ?

Even when you set jpeg quality to 100% the result is still lossy and damaged.  Its a scam.

[ChaosLord]

I can't remember which demo reel is which so I can't remember what year they came out so I can't remember how much chipram they required.

Here are the possibilities:
A. Needs 1MB Chipram

B. Needs 512k Chipram and somehow you have a program running on your Amiga that is using some of that.  Like for example you probably have 4 floppy drives connected and each drive use chipram buffers.  Or you have a hard drive connected which probably has very LARGE chipram buffers.

Reduce your chipram consumption and watch it start to work.

[ChaosLord]

So I'm wondering - why wasn't it popular? Why weren't there more paint programs or image converters to use dynamic-highres? AGA didn't come out until 1993 and dynamic-highres was around since 1990. It's unbelievable that for 3 years before AGA, there was the possibility to display 4096 colours in highres using software-only, but very few people were interested.

AGA came out in 1992.
"Dynamic Hires" has been around since 1985.  IIRC There are at least 3 different popular public versions of it.  And who knows how many private versions.

Was it the "dynamic-highres streaking" that turned people off? Digi-Paint allowed you to paint in HAM while minimizing HAM fringing, so it shouldn't have been hard to make a dynamic-highres paint program which minimized streaking. If you search Aminet now, there are a very small number of programs supporting dynamic-highres, SHAM or PCHG. Yes, AGA killed the need for dynamic-highres, but it had a whole 3 years to get popular and failed. Why?

It didn't fail.  Ppl still use it.

And you can do AGA Dynamic Hires better than you can do OCS Dynamic Hires since when you do it on AGA you get to easily have 256 colors on every scanline.  More than 256 colors per scanline with extra effort.

Using the simple method: 256 colors per scanline beats 16 colors per scanline every time.

You can also do Dynamic HAM mode but it is limited to 320x512 resolution  with 4096 colors on OCS.  But on AGA, Dynamic HAM can be 1280x512 with 16,777,216 colors.

[ChaosLord]

This type of method of enhancing still images was popular amongst a lot of the 80s home computers, at least on an app-by-app basis.

Yep!  I used the same type of method "rasterline interrupt color changes" on my C64 in 1983.

And it was very VERY useful on the Atari 800/400 computers which had a palette of 256 colors!  And no HAM mode.  So every good coder did "dynamic hires" on Atari 8-bit computers.  These are the computers that competed against the C64 and Apple ][+

The Atari 400 and Atari 800 chipsets were designed by Jay Miner who then took the idea to the next level in the Amiga.

[ChaosLord]

If you are able to get NewTek Demo #3 to run you'll notice that the resolution of the music playing in the background drops way down when displaying the dynamic-highres image...

That is either because you were using UAE or maybe they switched to lower res music because there wasn't enuff chipram laying around in the 512k chipram days.

I think the reason its not used more commonly is because the copper is leaving the CHIP RAM bandwidth starved...

Impossible on a real Amiga.

But I have seen and heard stuff like that happen lots of times on my WinUAE.

[ChaosLord]

And I would imagine the the PAULA has to share that as well?

Paula has its own 4 DMA channels that are permanently reserved for itself.

There is no such thing on Amiga as "oh no!  The gfx are draining to much electronz!  Its suxx0rizing all the quality out of the audio!"

That is the pc/mac way of doing things.  Not the Amiga way.


If you heard degraded audio then it was either
A: Your opinion, which you are entitled to.  (No one can like all bits of music equally)


B: It was degraded on purpose by the coder of the demo to save memory because that part of the demo was using all the chipram.  It was probably doing some hardcore double buffering or triple buffering or preloading an anim that would be shown later or etc.  There are a lot of reasons why it would run low on chipram and need to start using samples at a lower resoution.

> But I have tons of ram so that can't be it!

But it wasn't coded for your machine.  It was coded exactly and specifically for the machines of the day and had to work on them 100% guaranteed.
I think it was coded to work on 1MB Amigas with only 0.5MB chipram.



C: It might all just be an accident where the coder accidentally turned on the audio filter.  The audio filter makes everything sound "dead".  This might be exactly what you are hearing.

[ChaosLord]

If the CPU can't keep up then Paula would play whatever note it just played in a loop over and over until the cpu caught up.  It sounds really horrible and jarring and obvious when it happens.