[Coco] CoCo video?

[John Kowalski]

Hi Roger,

I don't have a hard drive on my CoCo, but with the "or less" qualification
in your question, the answer definately becomes YES - just drop the frame
rate until it reaches a data transfer rate the hard drive could sustain :)
All things considered, I think 320x200 running at 12 fps *may* be more
probable.  (I don't know the transfer rates of existing hard drive
interfaces is so I can't say for sure.)

If an existing hard drive interface does have DMA capability, even 24 fps
may be theoretically possible.  Someone else who's reading the list may have
some hard facts about transfer rates.

Not counting audio or overhead data, 320x200x24fps is 750K of data per
second (One megabyte every 1.36 seconds).  In clock cycles, that works to
2.33 CPU clock cycles per transfered byte.  That's too close to the CPU's
own clock rate for a software loop to manually read data that fast...  Even
the 6309's block transfer opcode is slower (at 3 clock cycles per byte.)



At 05:57 PM 29/01/2006 -0600, CoCoList for Color Computer Enthusiasts wrote:
>I've brought this up before but I forgot what conclusions we came 
>to.  Could the CoCo play a preformatted full-length movie from HD if each 
>frame was a raw 32000 bytes (320x200 16-color image per frame) @ 24 fps or 
>less?
>
>I'm not sure how these new IDE interfaces work, but if a DMA mode is in 
>there for pushing the sectors into CoCo RAM then perhaps we could tap into 
>that memory with the video pointer to show the frames quickly.
>
>As you can see from the Projector-3 sample renderings, 320x200x16-color 
>dithered images look quite well at about 4 feet or so back from the monitor.
>
>As for the audio track, I've used the FIRQ interrupt to play simultaneous 
>music in a few of my games and with the right buffering, I think the audio 
>track (mono, 8-bit?) could be pulled off.
>
>Correct me if I'm way wrong here but a 90 minute movie @ 24fps would be 
>90x60x24 for 129600 frames of 32000 bytes each, for a total of ~3.86gigs?
>
>As crazy as it seems, and as impossible as it is to get that size of a 
>movie into a CoCo HD... if the right PC software were made to encode such a 
>raw movie just for the CoCo, this could be pulled off, even if the results 
>are sloppy.
>
>If anything, this could be used as a demo at a CoCo Fest.
>
>-- 
>Roger Taylor
>
>
>
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>
                                         John Kowalski (Sock Master)
                                         http://www.axess.com/twilight/sock/