pouët.net

ChristopherJam information 2 glöps

• general:
• level: user
• personal:
• first name: Christopher
• last name: Phillips

• demo slideshow Amiga OCS/ECS elevation by The Electronic Knights
• bifat: very cool image codec. I like the work you did to minimize palette changes from one line to the next. It'd be interesting to try encoding the mtf transformed indices with an arithmetic coder (adaptive or otherwise), see if another smidge more ratio could be squeezed out :)
• isokadded on the 2024-04-14 09:49:40
• demo Amiga OCS/ECS TM2: Attack of the Ego Bots by Zymosis
• noby, sensenstahl: Scene quitting? Really? Why not just run with the time honoured "vote high for prods you like, low for prods you don't" and let the scene decide what to encourage people to produce next time?
  
  photon: you couldn't just slap this together with off the shelf components - the image codec is far crunchier than you'd get from png or gzip, and the only way we managed to get the art onto one disk. As mentioned before, I was recruited long after the art was underway, purely to assist with demo size. The purpose was never "show off cjam's codec, and krill's streaming and decrunch" but in the end that's part of what's on show here. And I gather the display tech is quite novel too. You may as well say "this demo could have easily been an .mp4 on a bigger computer" - which is true of every demo ever produced.
  
  4gentE: a newly created account isn't evidence of a sock puppet. It's pretty common for someone to not bother creating an account until they actually have something to say. (I remember being accused of being a sock puppet the first time I left a comment as Ars Tecnnica 🙄 - new account, siding with a woman against some misogynistic comments). And, I only created my account here so I could post in this thread too. (quick, someone PM christopherjam on csdb, tell him there's an imposter around :P)
  
  vurpo: no interest in controversy here - I just saw a fun technical challenge to bring across some ideas from my c64 4k cruncher.
• isokadded on the 2024-04-14 09:44:56
• demo Amiga OCS/ECS TM2: Attack of the Ego Bots by Zymosis
• Hi bifat, nice to meet you!
  
  Thanks Depeche 💜
• isokadded on the 2024-04-04 13:28:01
• demo Amiga OCS/ECS TM2: Attack of the Ego Bots by Zymosis
• Hey all.
  
  My involvement with this production basically came down some discussions on IRC, receiving a couple of raw dumps of test data, and sending a Python prototype codec. First I saw of the full production was watching the stream 6am Perth time on Monday :)
  
  
  Heavily paraphrased IRC logs, starting from back in early February:
  
  
  <krill> Is the stuff you wrote for bitpickler* adaptable for amiga? I've got some files that are too big.
  <me> Send me a .bin, I'll have a play..
  
  (* bitpickler is a cruncher I wrote for c64 4k demos, using a magic multiply-free tANS implementation and mixed context models)
  
  
  (Some time later - 4 bit values, ok. ...attempt to get a feel for the data characteristics by shaping it into a rectangle with an arbitrary stride and displaying it with matplotlib.. "ooh, this looks like it's a 640x480 image. I don't have the right palette, but it's probably.. some kind of comic, in a city?? Ok, I'll try and use context from last pixel or two, and maybe a pixel from the previous line. Oh, and a symbol to help with those big blank areas")
  
  <me> Ok, I can get it down to X bytes, about 50% of original - *much* smaller than you'd get from gzip or PNG. But the decruncher is pretty slow. Here are a couple of prototypes in Python, one's a slightly better ratio for 3x the work (context mixing), so the other's probably a better fit.
  
  <krill> Size (from faster one) is great! Imma port the decruncher to C.
  ....
  <krill> Ok, it's fast to decrunch on big computer.. but takes about 2m20s on A500.
  <krill> Seems like I'll need to port C to asm now and optimise the shit out of that
  ...
  (Insert some back and forth like Krill asking me if I can cut down the required shifts, because they're hella expensive on 68000, and me doing what little I could manage on that count, me trying some codec changes that didn't end up making the cut, etc. But mostly Krill optimising like hell while I buried myself in $dayjob)
  ...
  <krill> Alright, it's down to 13.75 seconds now.
  <me> Holy shit, nice work!
  ...
  <krill> Hi! For credits and such, how to bill you?
  (me, thinking - sweet! first amiga credit!)
  
  
  Some days later
  (me on discord, watching the live stream):
  [6:02 AM] ChristopherJam: ahahaha this is what i get for not vetting the content before agreeing to a colab…
  
  In hindsight I'd have probably requested we explicitly acknowledge the use of generative AI? Personally I'm mostly not a huge fan because most of them source their training data unethically. Beyond that it's just a tool - and it's not like I credit Vim, VICE, Photoshop, Python, Rust, ca65, etc when I do c64 demos.
  
  But like, mostly I release standalone crunchers, and what people use them for is their business really.
  
  and, MAD PROPS TO KRILL for getting a 10x speedup over the C version of the decruncher :D
  
  -cjam
• isokadded on the 2024-04-04 12:10:53