source vs target frame. This allows us to accumulate runs across
unchanged bytes, if they happen to be the same content value.
- introduce an allowable bit error when building runs, i.e. trade
some slight imprecision for much more efficient decoding. This gives
a slight (~2%) reduction in similarity on my test frames at 140 pixels
but improves the 280 pixel similarity significantly (~7%)
- so make 280 pixels the default for now
- once the run is complete, compute the median value of each bit in
the run and use that as content byte. I also tried mean which had
exactly the same output
- runs will sometimes now span the (0x7x) screen holes so for now just
ignore invalid addresses in _write
for runs of N >= 4.
Also fix a bug in the decoder that was apparently allowing opcodes to
fall through. Replace BVC with BRA (i.e. assume 65C02) until I can work
out what is going on
solver to minimize the cycle cost to visit all changes in our estimated
list.
This is fortunately a tractable (though slow) computation that does give
improvements on the previous heuristic at the level of ~6% better
throughput.
This opcode schedule prefers to group by page and vary over content, so
implement a fast heuristic that does that. This scheduler is within 2%
of the TSP solution.
bonus we now maintain much better tracking of our target frame rate.
Maintain a running estimate of the opcode scheduling overhead, i.e.
how many opcodes we end up scheduling for each content byte written.
Use this to select an estimated number of screen changes to fill the
cycle budget, ordered by hamming weight of the delta. Group these
by content byte and then page as before.
weight of the xor of old and new frames, and switch to setting the
new byte directly instead of xor'ing, to improve efficiency of decoder.
Instead of iterating in a fixed order by target byte then page, at
each step compute the next change to make that would maximize
cycles/pixel, including switching page and/or content byte.
This is unfortunately much slower to encode currently but can hopefully
be optimized sufficiently.
bytestream by prioritizing bytes to be XOR'ed that have the highest
hamming weight, i.e. will result in the largest number of pixel
transitions on the screen.
Not especially optimized yet (either runtime, or byte stream)
kris