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Old 17 November 2009, 02:41   #18
gulliver
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Join Date: Aug 2007
Location: The South of nowhere
Age: 39
Posts: 1,498
Amiga Video Format (AVF) - first draft - 16 nov 2009

Features:
Number of Colors 2,4,8,16,upto 32 (HAM8 and 16/32 bit modes are Not available for every Amiga, so NO)
FPS= 5,10,15,20,24,25 upto 30 max
Image size: maximum 320x200, 320x100, 160x200, 160x100, 160x50, 80x100, 80x50
Sound: max 8bit, 2 channel, 27429hz, min 8bit mono at 4410hz, also 8000hz and, 160000hz
Datarate: Should be a maximum that most interfaces can cope with it
Compression: File compression to save space and reduce bandwith at the cost of cpu usage based on open source publicly available compression formats on Amigas.

Philosophy:
The concept behind this format is that even a 1985 256kB kickstart 1.0 NTSC 7mhz 68000 Amiga maybe able to reproduce it without issues, provided the ide/scsi/whatever interface and its media can cope with the datarate performance wise.
This is most likely the limiting factor, not the cpu if adequate or no compression is chosen.
The advantage of the Amiga is that DMA and coprocessors can be used without affecting the cpu performance on playback.
It should be no problem to add HAM8, 16 and 32 bit modes, but then as said before will only run on few Amigas that have that hardware, the same applies to more framerate, image size, sound features. The point here, is that if you have great hardware and want better resolutions, then simply use another video format. This one is intended to be Amiga compatible pursuing the goal that any Amiga should be able to reproduce it, no matter if it is a 1985 unexpanded model.
The proposed format should be designed in a way that frame dropping, image and color reduction should be pretty easy and require very little cpu overhead from a video player program point of view.
Of course, with compression, at the cost of cpu overhead, you can reduce the disk interface clog and earn bandwith in the process, so that the most handicaped storage interfaces can cope with datarates. It is important however, to leave some little bandwith for housekeeping tasks, such as video&audio synchronization, subtitles, scenes selection, menus, and future improvements.

Datarate hipothesis (aproximates are rounded up on worst case scenario: no compression and highest paula sound quality):

32 colors 320x200:
video: 320x200x5bitsx30fps = 9600000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = aprox. 1.23 MB/s

32 colors 320x200:
video: 320x200x5bitsx25fps = 8000000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = 8438864 bits/s (aprox. 1.04 MB/s)

16 colors 320x200:
video: 320x200x4bitsx25fps = 6400000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = 6838864 bits/s (aprox. 835 kB/s)

8 colors at 320x200(NTSC low-res) with 30fps:
video: 320x200x3bitsx30fps = 5750000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = bits/s (aprox. 757 kB/s)

16 colors at 320x200 (NTSC low-res) with 20fps:
video: 320x200x4bitsx20fps = 5120000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = 5558864 bits/s (aprox. 679 kB/s)

32 colors at 320x200(NTSC low-res) with 15fps:
video: 320x200x5bitsx15fps = 4800000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = aprox. 640 kB/s

8 colors at 320x200(NTSC low-res) with 20fps:
video: 320x200x3bitsx20fps = 3840000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = aprox. 523 kB/s

16 colors at 320x200(NTSC low-res) with 15fps:
video: 320x200x4bitsx15fps = 3840000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = aprox. 523 kB/s

8 colors at 320x200(NTSC low-res) with 15fps:
video: 320x200x3bitsx15fps = 2880000 bits/s
audio: 2x8bitx27429hz = 438864 bits/s (aprox. 54kB/s)
Total = 3318864 bits/s (aprox. 406 kB/s)


by IFG 21:36

PS: I declare myself guilty of too much free time


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