26 June 2013, 19:41 | #41 | ||
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On the subject of four bitplane hires displays: If my math is correct, with an interlaced screen and nothing else accessing chipram (refresh cycles only), one 312 line field has 69264 available memory access slots and a 313 line field has 69486 available memory access slots. Running a 640x512 four bitplane display requires 40960 memory access slots leaving 28304 memory access slots on a 312 line field and 28526 memory access slots on a 313 line field. The CPU isn't fast enough to use all these slots. At most it can use half of them so on average there are 14207.5 memory access slots available to the CPU per field. Normally a two bitplane hires display or a four bitplane lowres display allows the CPU to use between 34632 and 34743 slots so the additional bitplanes in hires reduce CPU performance by up to 60%. The other half of the slots aren't necessarily wasted, though, and might be allocated to the COPPER, blitter, disk, audio, or sprites. |
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26 June 2013, 22:08 | #42 | ||
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joke aside, mc6809e yours technical comment are always very appreciated! beautifully and price explanation. thanx again, much things are cleared now. |
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27 June 2013, 00:09 | #43 |
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The Atari 2600 had just four color registers: Colump0, Colump1, Columpf, and Columbk. There is a single color for player sprite zero , a single color for player sprite one, a single color for the playfield (and ball), and a single color for the background.
That's a total of four colors. Any Atari 2600 game then that shows more than four colors on screen at once is proof. Qbert released in 1983 for the 2600 creates a six color screen. There are two colors for the sprites, and four colors for the background pyramid. Breakout released in 1978 also for the 2600 is an earlier example of changing color registers to increase the total number of on screen colors. It's no coincidence that one of the people responsible for helping design the 2600 went on to design the Amiga. Seeing the usefulness of changing color registers mid-screen, he invented the COPPER. |
27 June 2013, 00:27 | #44 |
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There is many proofs or not - it depends how deeply you start searching but believe - idea to change something in synchronous way with display is old as computing.
don't blow balloon - it can explode... |
27 June 2013, 08:58 | #45 | |
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(I just want to say that limitation of ST hardware, and far better competition machine: Amiga, push ST coders to do really amazing stuff! so "emulation of Amiga" is not a necessary a bad thing ) I bet that PCHG pictures looks better than HAM |
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27 June 2013, 09:43 | #46 | |
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So as we can use 64 colors in one line (or 32 or HAM) color changing was seen more like curiosity - impressive but not very usable feature. And you can loose bet - HAM is very powerful and definitely underestimated - with good converter especially one wit some tricks and modern quantization algorithms it can provide optimal conditions to display almost any type of graphic. There is lack of power on plain Amiga to use it frequently as HAM can be seen as compressed framebuffer thus processing is required to prepare data for framebuffer. HAM have also serious limitation - it is only LowRes. But anyway Amiga have HAM, EHB and Copper and we can use this, together with correctly processed audio (especially for ECS or AGA) Amga can provide broadcast video quality with audio over 15 - 17 bit dynamics - i would say as for 20 year old technology not bad. I really miss only one thing in AMiga - DSP similar to Falcon as standard from very beginning - even old TMS32010/32025 can be nice to have but... technology of 80's have own limitations. |
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27 June 2013, 11:53 | #47 |
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^
can you convert that three images to HAM? |
27 June 2013, 13:57 | #48 |
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I can do some experiment - prepare low res versions of those pictures with different types of color quantization.
For example plain PCHG (32 color LUT), PCHG EHB and PCHG HAM, also plain HAM. However as i wrote previously - as HAMLab is one of the best converters available for Amiga it still not produce best HAM possible, also it will not provide correct dithering for HAM but general dithering methods which are not optimal from HAM point of view. |
27 June 2013, 14:00 | #49 |
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so you do not have tools to produce best possible HAM pictures? just made them best as you can.
and also, can you send original files? I would like to try them on PhotoChrome on ST... |
27 June 2013, 22:25 | #50 | |
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Intuition, the windowing system of the Amiga, allows an application to open up its own screen with certain attributes, like resolution, number of colors, color palette, width, height, etc. But the Amiga is also a multitasking operating system, so there may be several programs running at the same time with different screen requirements. Intuition uses the COPPER to allow several applications running simultaneously to share the same display by changing the color palette, the frame buffer address, even the resolution, mid-screen. The top half of the display might show a 320x100 32 color screen, for example, while the bottom half shows a 640x300 16 color screen. It's an old trick made efficient by the COPPER and used in the Amiga from the start. Suppose that it does? There's very little CPU time left for anything else. With HAM, 70% of the CPU time remains for things like decompressing a HAM animation. How many animated Photochrome images have you seen? And DMA is still available for audio, blitter, copper, sprites, and disk. But if a programmer really wanted to he could page flip and use the COPPER to alter the 16 palette registers of a HAM image mid-scanline to improve it further. I think during HAM display the COPPER can perform 35 arbitrary writes to the 16 color palette available in HAM. |
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28 June 2013, 11:03 | #51 | |||
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I would not put Spectru512 in same basket as Intuition or NEOchrome... otherwise, Amiga capability to display different resolution on same screen is really impressive! how many?? like 50 per second: [ Show youtube player ] Quote:
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28 June 2013, 12:09 | #52 | |||
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http://en.wikipedia.org/wiki/Intuition_%28Amiga%29 Quote:
Nope - trailer is 24 fps (cinema film framerate), also this is STE not ST and modification of hardware are required to transfer such high amount of data from external storage - CPU is turned to DMA channel - nothing else - show us 12 - 24 fps movie with mono sound decent quality on plain ST. Quote:
AGA is capable to do even better video - with reasonable fast CPU and smart use latest video standards - for example using YCoCg space instead YCbCr thus reduce time required to color space conversion, with using some of techniques used by H.264 (integer transformations) there is a chance for compressed FMV, audio sampling rate can be higher without trickes and thus dynamic range easily can excess 90 - 100dB provide more than 16 - 18 bit quality on ordinary Paula DMA audio channel. Last edited by pandy71; 28 June 2013 at 12:34. |
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28 June 2013, 14:00 | #53 | |
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EDIT: The Netwek image wasn't actually HAM, now I come to look it up. You could do interlaced HAM but not HiRes. It did use palette changing trick though. I wonder if originally the idea came from the old arcade machines that used a monochrome screen with a coloured filter on top. Last edited by Mrs Beanbag; 28 June 2013 at 14:06. |
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28 June 2013, 14:38 | #54 | |
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Original idea for what? dynamic changes for color? |
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28 June 2013, 14:50 | #55 |
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Yes. They added different coloured strips over the top of the black and white screen, thus changing the colour of objects depending on their position on the screen. Kind of like physical copper bars I guess. Obviously it wasn't dynamic but it provided a more interesting picture.
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28 June 2013, 17:42 | #56 | |
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29 June 2013, 22:22 | #57 | ||
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2. so what? my point was that palette color changing was used in 1985. but not for displaying pictures. Quote:
(yours replays are almost always offtopic! - mc6809e ask me: "How many animated Photochrome images have you seen?" and I replay that this video is exactly that - Photochrome images displayed at 50 frames per second!) - it works on plain ST (of course without 50KHz DMA sound) and 512 color table - modification if required only if you want to have same high speed for writings! (without modification you will get only 0.5MB/s write; read speed will be 3.5MB/s anyway) why would you process sound at 18bit precision when you have only 8bit DAC in Amigas ?!? Last edited by prowler; 29 June 2013 at 22:40. Reason: Fixed quote. |
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29 June 2013, 23:13 | #58 | ||
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The Movie playback on Atari ST is truly impressive, my first thought was that the video must be a fake but I have looked it up and it seems real. I'll be honest I've never seen the like on the Amiga but then again it requires the video to be pre-calculated and streamed from a very fast hard disk because it couldn't decompress it fast enough. So it's a neat demo of what old hardware can do but not much practical use. I do wonder, to be honest, if you only come here to say "Atari ST is better than Amiga, ner ner". Quote:
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30 June 2013, 00:26 | #59 |
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30 June 2013, 00:34 | #60 | |||
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it was not clear to me
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You are confused - i never said 18 bit precision and usually i process sound on 24 - 64 bit precision even if target is 8 bit. I said that should be no problems to achieve subjective 16 - 18 bit dynamics - this is something else. How it works? - similar as 1 bit converters in HighEnd audio. |
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