Paula 'register dump' compression comparison

[pink^abyss]

This may be of interest for audio replayer coders that also want to try to write a compressed register dump replayer:

To see how well the new Pretracker 'register dump' pack alogrithm works I used it on a traditional tracked chiptune that uses a lot of 'random' commands ('Zapped Out' by 4-Mat!). It has been imported into PreTracker and new instruments have been created to replace the original samples. The resulting song was then stored as normal PreTracker file and as Pretracker register dump.
(For reference, the original Protracker module was also converted with Leonards LSP player, its the only player I know that also uses register dumps on Amiga, but it aims for speed, not data size).

The final size of the shrinkled PreTracker register dump is 6.023 bytes, which seems fine to be used within intros. Unshrinkled the song takes 19.030 bytes in memory.


You can listen to the result here:
https://www.pouet.net/prod.php?which=91611

[Samurai_Crow]

That's cool. I used to think that register dump compression would be useful for converting into Copper list playback such that the Copper would act as a feeder.

[pink^abyss]

Thats possible and would shave off a bit of rastertime. Also you can get rid of the cpu dma waiting. I would say you could save around 4 rasterlines compared to a pure cpu based solution, that needs 8 rasterlines DMA wait. Or you use Paula interrupts.. lots of choices with pros and cons. Personally I prefer the CPU solution because its the most simple does not really hurt on the performance side.

[WayneK]

And just to be clear, you are playing directly from the compressed register dump? There's no need to unpack the register dump in memory before playback, right?

[pink^abyss]

Originally Posted by WayneK

And just to be clear, you are playing directly from the compressed register dump? There's no need to unpack the register dump in memory before playback, right?

The whole dump is not unpacked to memory. Instead each frame '16 words' are unpacked from the compressed dump into a '16 words sized' buffer. 16 of such buffers are needed. From these buffers the Paula registers are fed.