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Old 18 November 2009, 00:26   #43
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Join Date: Sep 2007
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Age: 40
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Originally Posted by gulliver View Post
Why HAM6 is not feasible from my point of view:

Well, if the proposed Amiga Video Format draft is taken into account, due to the way HAM works, in an attempt to move an image around the screen (such as subtitles, timing info, etc) will generate noticeable fringing that will degrade the quality of the image a lot. This is typical behaviour of an Amiga in HAM mode trying to move a blitter object around.
Also it has restrictions on color combinations between adjacent pixels that can only be avoided with careful planning and a few neat tricks. So I think no.
You want to leave out Ham6 because possible subtitles might not look so good? That's a mistake, see after the quotes. Subtitles would only be possible if you reserve two colors, using the closest colors in the palette may result in unreadable text. Also, you don't have 32 selectable colors anyway, because you need the screen color to be black at all times, or the borders will change colors all the time. That leaves 31 colors for the frame...
Originally Posted by gulliver View Post
Changed my view on EHB:

While not present on the very first few A1000 NTSC models sold in USA and Canada, it sure provides 64 colors, so it could be implemented provided the player program checks that the EHB mode is available, and if not just ignore the offending bit and play the video at 32 colors. In this case we have to be carefull on datarates, which will obviously raise.
When you leave out the 6th bit from an EHB image, you'll get an ugly looking image, so that's not a good idea.

About the subtitles:

What would you need sub titles for anyway? It's not like watching a movie in this kind of format would be a very pleasant experience, and what's the point? You'd have to convert the whole movie to raw, and then you have to convert all the frames to something the Amiga can display properly. Doesn't sound like anything that's going to be used for such purposes. An hour of video in this format already uses up about 3600 MB, so you'd need a dvd drive on your Amiga to use the video.

EHB and 32 colors will most certainly look uglier than some Ham fringing, so Ham 6 certainly has to be an option. It's better that way anyway. Let the maker of the video decide what image format to use, rather than to limit them to EHB or 32 colors.
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