Frogger is slow on my MMU '030 playing VCD

[Karlos]

For enjoyable non-hardware based mpeg decoding on a miggy you need

1) A fast, DMA driven drive. PIO will suck the CPU dry even before you start decoding anything.

2) As fast a CPU as you can get with the largest bandwidth memory access you can manage. Nothing less than a good 060 (CS MK3 or CSPPC with 64-bit bus access is about as good as classic 680x0/PPC will get) will have sufficient power. A lot of number crunching is involved.

3) The fastest possible graphics bus you can get. Basic 640x480x16bpp video at 25fps requires 14.7 MB/s.

I've studied the results of quite a few classic amigas and TBH, the only cards I have seen that can sustain this kind of continious copy speed (or beter) from fast RAM to VRAM are the BVisionPPC/CVisionPPC and some PCI cards running on GRexx. The majority of mediator and prometheus systems seem to max out at about 8-10MB/s for this kind of operation.

Of course a lower resolution helps; 320x240x32bpp at 25fps (which needs 7MB/s copy speed) is achievable by pretty much all existing cards.

Some cards, notably those that support overlays and such can accelerate some aspects of video playback. Overlays can typically use YUV data directly and perform scaling which saves the CPU a lot of work.

[Karlos]

@crumb

You have to make sure you write your data to VRAM in the widest possible units to get a fast throughput. For 24-bit packed pixels (3 bytes per pixel) that can be a bit of an arse to do - you'd ideally want to buffer some amount of data thats a common multiple of 3 and 4 bytes and shove it along as 32-bit words (well, for zorro3 at least - I expect it makes less difference for zorro2 cards). For 68040/60 I found that move16 works well on quite a few z3 / PCI cards :-)

[Karlos]

@hyperspeed

We didn't lose the plot. We are discussing the factors that influence the performance of mpeg playback on classic amiga hardware. A 68030/30MHz + AGA is really asling a tad too much, no matter how great the playback software is.

As for graphics memory write speed, AGA is on a par with a Z2 graphics card (max about 7MB/s) which is sufficient for 8-bit playback. Can look pretty good in HAM8 too. But of course this means your absolutely need as fast a CPU as possible - converting 24-bit RGB to some sort of planar HAM8 isn't exactly a cakewalk. An 060 starts to become essential.

Nobody is slamming the "integrated" 1200D, but it is over 10 years old now - you need to expand it to get much joy these days. I had one that was absolutely crammed to the brim but eventually a tower was essential if it was all to survive.

Now I have another 2 1200D's to go along side it that I have no intention of towering ;-)