[Coco] CoCo video?

[Gene Heskett]

On Sunday 29 January 2006 20:22, John Kowalski wrote:
>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.)
>
The 6x09 doesn't, without extensive hardware help, support dma, so the 
max transfer is going to be someplace in the 12 seconds per megabyte 
moved area, and this doesn't address the "are we done with this block" 
conditional tests to terminate the movement of the individual field so 
that an outer loop can reset the 'to' register thats addressing the 
video memory.  That also will require they be mapped into the same 
space, a bit of trickery at init time.

Based on that, it might be a doable thing. But I'll let you fellows 
figure the achievable frame rate.

A far larger problem is that it will be silent since the audio data will 
actually take up as much or more data space than the video even if its 
only 6 bit sound.

But its an intrigueing mental exersize to calc all the what ifs. :)


>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
>>
>>
>>
>>--
>>Coco mailing list
>>Coco at maltedmedia.com
>>http://five.pairlist.net/mailman/listinfo/coco
>
>                                         John Kowalski (Sock Master)
>                                        
> http://www.axess.com/twilight/sock/

-- 
Cheers, Gene
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