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Started by cpcitor, 22:21, 03 November 21
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Quote from: megachur on 07:38, 08 November 21Firstly : Yes it's a good idea but what do you show with this analysis ? that some emulators are using filter and others not !? what do you use to record the sound of the real hardware on amstrad cpc !? using stereo cable and a very, very good sound card without filter ?
Quote from: megachur on 07:38, 08 November 21Secondly : this youtube video have very bad sound...
Quote from: megachur on 07:38, 08 November 21and yes YM2149 (2Mhz) and AY8912-2 (1Mhz) are very similar.see this source for the real hardware analysis done years before for mame emulator :https://github.com/mamedev/mame/blob/master/src/devices/sound/ay8910.cpp
Quote from: megachur on 07:38, 08 November 21The conversion of atari st songs have allready done some year ago.... the first one have been done by Longshot if I remember correctly : see https://www.cpc-power.com/index.php?page=detail&num=7799.Most of them here : https://www.cpc-power.com/index.php?page=staff&lenom=Transfert%20Atari%20STIt's simple : convert the 68000 code to z80 code then divide frequencies to have correct sound on 1Mhz AY !
for p=2 to 25 : sound 2,p,50,15 : next
Quote from: cpcitor on 08:46, 08 November 21What do you mean? How is it bad?
Quote from: zhulien on 17:16, 10 November 21What is the technical reason that 1 sound channel on the AY cannot simulate a spectrum's beeper as per above?
Quote from: zhulien on 17:16, 10 November 21The sound chip isn't the only way the CPC can make music. You can also click the tape motor on and off fast on a 464. I don't know if you can 'control it' but, has anyone tried to control the faint buzzing of the z80 you hear at night when you do certain tasks?
Quote from: zhulien on 17:16, 10 November 21If a beeper on a spectrum can sound like this: https://www.youtube.com/watch?v=L4LSHnMhFPU
Quote from: zhulien on 17:16, 10 November 21(Interesting technical page about how spectrums can achieve multichannel sound using a beeper https://www.gamejournal.it/the-sound-of-1-bit-technical-constraint-as-a-driver-for-musical-creativity-on-the-48k-sinclair-zx-spectrum )
Quote from: BSC on 23:06, 10 November 21I think there are a couple of reasons why the sound of the beeper engines can not (easily) be reproduced on a CPC using the AY:1. Much slower access to the sound chips registers, yielding a lower max replay frequency2. I believe the beeper, even though it is programmed in a digital way, i.e. only 0 or 1 is possible, does in fact work very much like an analog(ue) device, the hardware geeks here might be able to say if I am wrong or elaborate further, but I think if for example you toggle from 0 to 1, then hold for a very short amount of time before toggling back from 1 to 0, the beeper (which is a tiny speaker that is directly connected to port &fe) will not have fully moved to its maximum displacement, but only a fraction of that, depending on the amount of time 1 was active.
Quote from: BSC on 23:06, 10 November 21I was planning to make more experiments, like manipulating a single volume register directly instead of going through the envelope generator (that was done purely out of curiosity) or actually using the tape port (port &f5) which might result in more speccy-like, albeit really delicate, sounds.
Quote from: BSC on 23:06, 10 November 21I have done some experiments using the envelope generator, they are on soundcloud:https://soundcloud.com/betasoftcologne/4bit-sweeping-demohttps://soundcloud.com/betasoftcologne/cocio-and-finsprit-6-channel-preview
Quote from: megachur on 17:53, 10 November 21Just hear it on the real Atari ST and you will understand what I mean ! Even some Atari ST emulator feature no right 2Mhz YM emulation...
Quote from: cpcitor on 18:58, 04 November 21xcellent! Thanks! This is the best output so far.Is it Arnold Emu by Kevin Thacker?Which version of Arnold is it?
Quote from: cpcitor on 10:29, 11 November 21Note sure I agree with 2 as an argument. First, is the beeper on the CPC very different from what can be plugged on a spectrum?Let's admit the speaker will not reach maximum displacement, but so what ? Let's rephrase.The speaker provides sound by pushing or pulling air.Effects of high speed bit flipping put the speaker closer to a not saturated but linear regime, where frequency domain analysis provides hints.In other words, at high base frequency, the harmonics will get dampened, right. At which frequency does this happen?To get a hint, we'd like to guess the range of frequencies the speaker can provide. Easiest is to ask what frequencies are emitted, disregarding if those are harmonics or even the fundamental.The answer is : above many kHz, as people report hearing sound from the CPC even with periods as small as 5.This is why those musics on the spectrum sound scratchy, and on the CPC, too.But all of this does not explain IMHO why the beeper engines can not be easily reproduced on the CPC.I would rather say: with one bit-banging output, the Spectrum developers had no choice but to explore what happens when varying delays between highs and lows.The CPC's AY chip can modulate while the Z80 does other work, but with less control (especially no PWM), and got people accustomed to that.In some sense the CPC has some unexplored potential, yet how that can be combined feels a tough space to explore.
Quote from: cpcitor on 10:29, 11 November 21On a CPC you can control the tape signal output "very" quickly (Z80 OUT takes 'µs or 1/250000s on the CPC). About 5 times quicker than the fastest PSG access.So, I recently had the idea of a "tape demo". You put a cassette in your CPC464, press "record", run the code, you hear a low volume music while tape records. Then you put the cassette in a regular player and it plays something "remarkable".(If you're sad enough to own a CPC 6128, you can plug a cable on the DIN and either connect that to you audio amplifier or to a tape recorder.)
Quote from: cpcitor on 10:29, 11 November 21Interesting. Could you share what parameters are set and are changing in each section?I can't even say if the sequence of sections repeat periodically or not.
Quote from: BSC on 21:18, 14 December 21I am not sure if I follow you on what you wrote concerning frequencys and harmonics. Care to elaborate?
Quote from: BSC on 21:18, 14 December 21Anyway, there is no "beeper" in the CPC as is in the Spectrum. The beeper I was referring to is the envelope generator of the AY.
Quote from: BSCbeeper (which is a tiny speaker that is directly connected to port &fe)
Quote from: BSCYes! I think the tape "beeper" is a good approximation of the Spectrum one. Have you already tried this approach?
Quote from: BSCRegarding this:https://soundcloud.com/betasoftcologne/4bit-sweeping-demoI think it consists of 4 virtual oscillators which trigger a re-start of the envelope generator shape every time one of the oscillators"transitions" from low to high or vice versa. The envelope shapes vary throughout the track, every 3 seconds, but I don't recallwhich exact shapes were used at what time, but all of them were of the non-repeating type. And the oscillators were only a fewhertz apart each, like 400, 403, 406 and 409, to get a lot of beating.And regarding this one:https://soundcloud.com/betasoftcologne/cocio-and-finsprit-6-channel-previewThis is basically the same as above, but with 4 oscillators for the bass and 2 for the lead and I think the frequency difference waseven smaller, like 1 Hz apart.
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