Hmm ... as far as i have seen, the LZ4 decompression is faster than raw-byte reads
You need to be careful when making statements like that. For example, the above statement can only be true when the decompression rate exceeds the disk transfer rate AND the compression ratio is significant. On an Apple IIgs (and most 8-bit systems), with the data I believe you're referring to, this is common. For my platform (8088) this is not the case. If you want to see actual tests I performed with their decompression times and compression ratios, refer to the link in my previous post; I found only a single case (heavy use of RLE) that outperformed raw reads, and only because the CPU had an optimized instruction for doing so.
Regarding Apple II storage, there are several solutions using DMA and archive transfer rates of over 200k/s on the Apple //e (1mhz).
Kilobits or kilobytes? Important distinction! If KB/s, then 200KB/s is definitely fast enough to support video playback in this way. Heck, if you've got 200KB/s then don't bother with any compression; DHGR is 140x192x16=~13KB per frame so even without any processing you can achieve 15fps right there.
But as on the PC, the use of the API will result in unpredictable data transfer rates.
In those cases, you create a system that can be tuned for the available bandwidth (which is what I did) and just make sure you stay within the slowest conditions you are likely to encounter.
What is your thought of accelerating the 8088 (NEC V20 or upgrade-cards)?
Can you be more specific? What about accelerating the 8088 do you want my thoughts on?
What is the limit of upgrades to the XT until it is no longer interesting to you?
When I used these systems as a teen in the 1980s, I enjoyed hotrodding them. I installed an NEC Vx0 chip, I lusted after accelerator cards, I cut holes into my case to add drives, I added a math coprocessor, I added a hardcard, I ran speaker wires out to a jack so I could amplify the speaker, etc. (
Sample video for one of these systems, if you're curious)
Now that I program them for the challenge, I don't enhance them at all. The fun, for me, is breaking previously-established limits with stock hardware, or at the very least, using hardware that was available at the time.
Put another way: If I had chosen an accelerated machine with which to develop my video playback system, I would have designed something completely different (likely a VQ scheme that performs actual heavy lifting). But then again, it's not really that impressive to say that you've created a video system for a 50MHz machine, is it?