[Coco] CoCo Video Player Project

[Mark McDougall]

Nick Marentes wrote:

> The real challenge is the decoding of a compressed video format fast 
> enough on a CoCo3 to have a reasonable frame rate. That Timex Sinclair 
> demo seems to be doing that...but would anyone really want to watch a 
> black and white blocky (text block based) video??

I think if you're attempting to play compressed video, you can forget about 
doing it on a Coco unless you're happy with restricting the frame rate / 
resolution even further. You may be able to implement something like RLE, 
but that's pretty much useless for anything other than "cartoon-style" graphics.

An ATA IDE controller in PIO mode can transfer data up to 16.7 MB/s - 16-bit 
mode. Obviously the Coco can't sustain anywhere near that data rate, so the 
video problem with _always_ be CPU-bound. Having said that, I can't speak 
for the performance of the Coco IDE controller implementations.

I'm assuming from Mark Marlette's comments in another thread that the Cloud9 
controller is based on an Altera CPLD - you can implement an entire IDE 
controller running in UDMA mode in an Altera FPGA - so there should be no 
problem running PIO mode 4. Though IIRC, PIO rates define _minimum_ cycle 
times, and there's no reason why the controller can't extend them if the CPU 
can't use the bandwidth. Mark would have to comment on the implementation in 
his controller.

So again, can anyone comment on the sustained throughput available on a 
Coco3 reading data from an IDE drive, assuming the data is simply copied 
into a linear buffer on the Coco? That's your starting point for estimating 
the feasibility of such an exercise.

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"