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CSI 5k   [2020]

CSI 5k Released by :

Release Date :
15 January 2020

Type :
C64 Intro

Released At :
Intro Creation Competition 2019

User rating:awaiting 8 votes (2 left)   See votestatistics

Credits :
Code .... ChristopherJam

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Production Info
Submitted by ChristopherJam on 15 January 2020
The intro places a 320x176 bitmap in the area from $2000 to $3b80, but restores that entire area of RAM upon exit. It does this by taking advantage of tiles that contain less than four colours to leave some bits undisturbed, and swapping the remainder with the bitmap source stored from $1168 to $1bf5 (2702 bytes). Each character row has its own background colour, so the exporter can choose the one that maximises the number of "don't care" bits for that row.

The routine that swaps the bits in and out uses a small VM with four opcodes, and an implicit loop around each of the three scripts. Cheers to White Flame for rekindling my interest in VM implementation.

Intro contains the first 97.3 seconds ($1300 frames) of Ben Daglish's "Future Knight," recrunched down to 927 bytes of code and data.

The tiny player supports triangle LFOs for frequency and pulse width modulation, an alternate control byte for the 2nd and 3rd frames of each note, and 8 bit floating point frequency values. Like the original full tune, it doesn't loop. It's also the slowest player I've ever written - each voice reads from three separate compressed bitstreams once per note, to acquire a tuple of indices for frequency, duration, and instrument. The original tune barely touches the ADSR values, so those are handled out of band.

Including the entire tune would have cost an extra 522b of data, as well as needing support for a third control value for some of the instruments. This would have taken the demo up to around 5.6KB

Thanks to Krill for always being willing to lend an ear about compression codecs and code golfing, for discussions about the pros and cons of potential release schedules, and for general inspiration about getting stuff out the door.

Lastly thanks to my wife Jeanette, for supporting me working on this thing over my holiday break, and well over a week past when I was hoping to have this done and dusted.
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CSDb (Commodore 64 Scene Database) is a website which goal is to gather as much information and material about the scene around the commodore 64 computer - the worlds most popular home computer throughout time. Here you can find almost anything which was ever made for the commodore 64, and more is being added every day. As this website is scene related, you can mostly find demos, music and graphics made by the people who made the scene (the sceners), but you can also find a lot of the old classic games here. Try out the search box in the top right corner, or check out the CSDb main page for the latest additions.
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