Negative Charge

Trying out some visualisation effects in the player, making better use of the space and moving the track metadata into the scroll text. Broken a few things along the way, but so far working okay even with the software bass active. Now to reduce the number of cycles it takes to display. 🔊

Acorn Electron版 AWASS #acornelectron
inufuto.web.fc2.com/8bit/awass/#...

I thought I'd give the Acorn Electron port of the Squeeker Plus 1-bit engine a go, not expecting much considering the demands on the faster BBC Micro. However, venturing into the murky realms of illegal NMOS 6502 op codes, it's playing!.... badly, but it's at least recognisable with its issues.

A bit of an improvement... pitch is now right, and track length matches the ZX Spectrum version. Drums, however, are still way off...

Very much a work in progress, but quite a while ago @h0ffman.bsky.social shared his .1tm file for 1-Bit High and Rising. The intention was to port the Z80 Squeeker Plus engine to the 6502, but it proved to be difficult... until now.

Pitch is wrong.... but it's finally playing . More work to do! 😊

I think it’s most likely a combination of poor choice on my part using Mode 5 with double width pixels, rounding errors and orthogonal projection. I have a version that implements perspective but broke the backface culling.

Today's demo effect on the BBC Micro... the iconic spinning cube. Here's a very basic version with backface culling. I wasted 10kb on double buffering, so there's only room for a short sound loop on this one. There are much better spinning cube examples already on the Beeb. 🔊

Today we have a classic scroller on the BBC Micro with a slight twist... custom font scaled dynamically to 16x16 pixels and continuous gradient applied to give the impression of more colours than supported by Mode 5. All software scrolling (no CRTC abuse) so works on the Acorn Electron too. 🔊

Another attempt at a BBC Micro Mode 7 demo effect today - the Moiré pattern. Could do with some colour and further optimization, but just wanted to get the basic effect working. This demo is accompanied by some classic Mad Max {Jochen Hippel) music. 🔊

#bbcmicro #demoscene

Thanks. I‘m going to have to get my head around vertical rupture at some point, but putting that off for now. I’ve a few other effects I want to try first and then I may return to the CRTC. So far the effects haven’t been too timing critical so music with software bass works with them.

More 6845 CRTC experimentation on the BBC Micro. This time it's Mode 1 and an infinite vertical scroller. I'm probably not doing this right as it's not as smooth as I would expect. Need to do some more reading on this one. No music with this demo.

#bbcmicro #demoscene

Experimenting with the BBC Micro's 6845 CRTC to do some smooth full screen hardware scrolling. Not something I've attempted before and I can see a number of possibilities. This is a simple Mode 5 dynamically generated gradient that I'd have a lot of difficulty moving at this speed in software. 🔊

Today's demo effect on the BBC Micro... water ripples. This would be much better in higher resolution so I may try a Mode 1 or 5 version. It doesn't quite follow the original algorithm due to the resolution constraints. 🔊

#bbcmicro #demoscene

Another demo effect on the BBC Micro with music... it was going to be a dot tunnel demo but I haven't yet got the tunnel effect working, so here's a variant. 🔊

#bbcmicro #demoscene

Today's BBC Micro demo effect.... it was going to be a rotozoom, but I can't get the rotation looking right or at a reasonable speed at the moment, so here's a panning, zooming checkerboard with music. 🔊

Experimenting with trying to recreate some classic demo effects on the BBC Micro, starting with plasma. The version I have in Mode 5 looks better, but was slide show speed so moved to Mode 7. Needs more optimization, and the plasma effect can be improved. Added some music too. 🔊

Ok, this is about as complete as it will get 😊 Here's a preview... I'll tidy up a few things (maybe change the music) and post on Stardot. 🔊

No, it’s Mode 4. Placeholder background at the moment.

XOR’d direct to screen memory

Stage 2... need to optimize the snow fall some more, and then add the interrupt-driven music. 🎅

Not sure where I'm going with this yet, but I'm determined to make a little festive demo for the Acorn Electron. I have some music ready. Watch this space. :-)

I think the best way is to decode the whole file and compare the output with the original, uncompressed version. If I find time I’ll give that a go. Your code is significantly different from DMSC’s original with the use of the buffer offset, so not easy to compare directly.

Ah, okay. I’m using the original code I linked to from DMSC. check_end_song looks correct to me there unless I’m missing something?

Thanks! Trying to locate the issue in the original code. Is your fix the addition of the bne and bcs here?

github.com/dmsc/lzss-sa...

I've released a beta of the first BBC Micro David Whittaker Music Disk here: www.stardot.org.uk/forums/viewt...

Looking to get some feedback on compatibility with real hardware before I publish the final version to my website. Still may be one or two small bugs to fix.

I now have the ability to use 16kb of main memory if no SWRAM is present on the device, so those without at least get to hear songs that fit into that space and partial songs from those that don't. This also works for songs where you don't have enough SWRAM banks to fit the whole track.

Getting closer to releasing a whole batch of music disks I've put together for the BBC Micro. Spending some time on cycle-optimising the music driver as even two or three cycles make a difference when called in the main play loop. At the moment it requires SWRAM - about to fix that...

Here's a hint where I'm going with this sample sequencer. I've moved the playback loop to zero page and leave the WE (write enable) active which allows output of 16kHz samples (although memory becomes an issue). Need to combine this with my SN76489 conversion of the SID.

It's mightily impressive. Chris is the master. I've something slightly different in mind... sample playback alongside SN playback.

Just a little something I'm working on. This is RLE encoded for fast playback, but I'm sure I can compress the samples better to fit more in memory / SWRAM.