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/* Weblinks */
== Weblinks ==
* https://pulkomandy.github.io/shinra.github.io/willy.html
* [http://www.roudoudou.com/ACE-DL/ OPL3 Player PackArchive ZIP] Huge pack containing 3887 OPL2/OPL3 tunes to be played on Amstrad CPC* [https://opl.wafflenet.com/ The OPL archive] [https://vgmrips.net/packs/chip/ym3812 VGMrips OPL2] [https://vgmrips.net/packs/chip/ymf262 VGMrips OPL3]
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== Compatible Serdaco soundcards ==
*[https://www.serdashop.com/S2P S2P soundcard] aka Roland MT-32 or General MIDI Wavetable Synth Synthesizer - based on SAM2695 (2014) - [[media:SAM2695.pdf|Datasheet]]*[https://www.serdashop.com/OPL3LPT OPL3LPT soundcard] aka AdLib Gold or Sound Blaster 16 - based on OPL3 (1990) - [[Media:YMF262 199110.pdf|DatasheetOPL3 datasheet]] [[Media:Yamaha yac512 datasheet.pdf|DAC datasheet]]*[https://www.serdashop.com/OPL2LPT OPL2LPT soundcard] [https://github.com/zjuyzj/OPL2LPT-Replica OPL2LPT-Replica] aka AdLib or Sound Blaster - based on OPL2 (1985) - [[media:Yamaha_YM3812.pdf|Datasheet]]*[https://www.serdashop.com/CMSLPT CMSLPT soundcard] aka Creative Music System or Game Blaster - based on two SAA1099 (1986) - [[media:Philips_saa1099.pdf|Datasheet]]*[https://www.serdashop.com/TNDLPT TNDLPT soundcard] aka PCjr or Tandy Sound - based on SN76489 (1979) - [[media:Texas_instruments_sn76489an.pdf|Datasheet]]
*[https://www.serdashop.com/CVX4 CVX4 soundcard] aka Covox Speech Thing - [https://scalibq.wordpress.com/2017/11/28/the-covox-years/ Technical analysis]
Note: Unlike the [[AMSDAP]] OPL4 & YRW801 ROM solution, the S2P soundcard natively supports Wavetable MIDI without requiring a software translation layer. The Willy with S2P soundcard recreates what it was like to connect an Amstrad CPC via a [[Music Machine]] MIDI port to a Roland MT-32 synthesizer in 1987.
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== Technical information I/O Ports ==
2 ports are used to control the MIDI soundcard: &FEAC for data, and &FEAD for control and status.
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The OPL3, released by Yamaha in 1990, is an upgraded version of the OPL2, which came out in 1985. OPL3 is register compatible with OPL2, with twice the number of signal sources, 4 new operator modes, 4 new selectable waveforms (including square wave) , and stereo output.
OPL3 offers 18 FM 2-op chans in its standard mode, but that can be configured:
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The most basic elements of an OPL FM synthesiser are:
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===Operators = Waveforms == On an OPL1 or 2, each channel consists of two operators. On an OPL3 it may also consist of four. In either case, the basic FM synthesis operation is the same: The output of one operator is used to modulate the current phase of another. The former is known as the modulator, the latter as the carrier. In two-operator frequency modulation mode, the output of the carrier, after modulation, is the audio output. In four-operator mode there are some more complicated options involving routing outputs between operators. <br> === Logsin and Exponent tables === The OPL chips use two look-up tables, each containing 256 entries. [https://g.co/kgs/Da1vEi4 Source] They produce the sound without any multiplication or other costly arithmetic operations, using for 2-op "frequency modulated" (actually phase modulated) synthesis the formula: out = exp(logsin(phase2 + exp(logsin(phase1) + gain1)) + gain2) ==== Exponential table ==== x = 0..255, y = round((power(2, x/256)-1)*1024) When such a table is used for calculation of the exponential, the table is read at the position given by the 8 LSB's of the input. The value + 1024 (the hidden bit) is then the significand of the floating point output and the yet unused MSB's of the input are the exponent of the floating point output. ==== Log-sin table ==== x = 0..255, y = round(-log(sin((x+0.5)*pi/256/2))/log(2)*256) This is the first (rising) quarter of sine wave. The rest can be constructed by flipping all the bits of x and/or by changing the sign of the samples. <br> === Waveforms ===
The original OPL only has access to the sine wave.
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FM synthesis does a great job relative to its hardware requirements at reproducing melodic instruments but isn't especially useful for harsh percussion noises like drums. Yamaha provides separate drum noises for this purpose. The programmer has to forfeit three channels of regular FM synthesis, freeing up six operators for five rhythm instruments.
A global random level generator is implemented for this mode; it's a standard LFSR just like the noise generator on simple chips like the AY-3-8910 or SN76489, so it provides a one-bit semi-random output.[https://www.reddit.com/r/EmuDev/comments/gdhjt0/a_primer_on_fm_synthesis/ Source]
The OPL can then generate:
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== OPL3 undeserved reputation ==
The OPL3 soundchip has been underused and unfairly criticized, largely due to 2 factors:
* As OPL3 is compatible with OPL2, PC game producers did not make the effort to specifically exploit the OPL3 soundchip capabilities, instead they relied on inferior OPL2 tunes. These are the equivalent of the Speccy ports that gave the Amstrad CPC a bad reputation.
* Western PC game developers in the early 90's also tended to produce music by using a master MIDI track on Roland MT-32, and then downgrading it for the various PC soundchips. The result was a cheesy so-called "MIDI" music. That was unfair for OPL3 (but also for MIDI, as Wavetable MIDI sounds way better than that).
=== Examples of proper OPL3 music ===
* [https://www.youtube.com/watch?v=a7I-QmrkAak MoonDriver]
* [https://www.youtube.com/watch?v=uyVOy02tW88 Paul the Penguin]
* [https://www.youtube.com/watch?v=6JlFIFz1CFY Zen Challenge]
[[Category:Music and sound]] [[Category:Peripherals]]
