FRS' MSX page WIP

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By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

18-08-2017, 00:33

ricbit wrote:

Do you plan to release source code for the new tr drivers? I could add my carcara basic improvements in the patch.

Yes, I plan to open source them, but not right now. The driver uses my HIDlib library (*1) that I also plan to release as open source. But HIDlib requires a lot of documentation to allow programmers to use it properly, specially the whole part of the signature of the devices, as this was a de-facto standard. And this documentation is only partially done. This documentation will also allow new hardware to be created according to the standard.

*1: yes, joylib has grown to become HIDlib, as it now supports way more than just joysticks/joypads. Joylib is now only one of the libraries inside HIDlib.

By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

19-08-2017, 15:32

@Grauw

If your turboR is an FS-A1GT, there's an easy fix for the jailbar problem. If you wish, I can publish the fix in my site alongside with its audio fix.

By Grauw

Ascended (8457)

Аватар пользователя Grauw

19-08-2017, 18:23

Hey FRS, thanks for your elaboration! Interesting to know.

About recapping, I thought in general it was a good idea to do for these old machines, but if you say the Japanese caps from the early 90s were not affected by the faults that many caps from the 80s-90s suffer from, I’ll trust you on that and save myself a lot of work Big smile.

About jailbars in the video output of my GT, I had figured that these were maybe the result of bad caps, where the rgb signals maybe weren’t held long enough by the caps, but it was a bit of a shot in the dark. The jailbars are pretty prominent on most solid coloured backgrounds (on my two Samsung flatscreens), for more colourful pictures it’s not so visible so I’ve been able to ignore it, but it’d still be nice to fix.

I note that the jailbars aren’t visible on a black, gray and white background (color 0, 1, 14, 15), are near invisible on bright yellow (color 11) and not so visible on medium red (color 8). Maybe that has some relevance.

[Edit: I also played around with the palette values, (0,0,0) through (7,7,7) did not show any, I didn’t see any for (0,0,0)-(0,0,7) either, for (0,0,0)-(7,0,0) I see some, stronger for (0,0,0)-(0,7,0), and also stronger for mixed values the further they deviate from the grays. They seem to be about a pixel wide. The lower frequency bands you see on the image below are moiree from my camera.]

By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

19-08-2017, 20:06

Ok. Those jailbars you're seeing are a design mistake on the A1GT. But it's an easy fix.

I'll publish the solution so you can fix the jailbars on your machine at the same time you'll do the soundfix.

BTW, was this picture taken from the RGB, s-video or CVBS output?

By Grauw

Ascended (8457)

Аватар пользователя Grauw

19-08-2017, 20:21

Looking forward! It is SCART RGB.

By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

19-08-2017, 21:26

Done. I have just published the fix for the jailbars on the FS-A1GT RGB output. I hope it helps you. :)

By Grauw

Ascended (8457)

Аватар пользователя Grauw

19-08-2017, 22:11

Haha, that surely is one of the easiest fixes ever! I had expected to at least have to replace a resistor or something, but none of that Smile. The hardest part was to remember how to open the turboR’s case Big smile.

And it works like a charm! Perfectly smooth image now. Wow, many thanks for that. So much better.

Very elegant fix, too, Panasonic should’ve just done it like that in the first place, instead of hiding it behind some jumpers on the motherboard…

By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

19-08-2017, 22:12

You're welcome. Smile

By sd_snatcher

Prophet (3072)

Аватар пользователя sd_snatcher

19-08-2017, 23:52

Since my statement about the Micro Cabin using the PSG as a 3rd operator for the FM sound seems to have been controversial (MRC sadly even edited this info out of that news), I think it's better to show what exactly it means.

There's one specific song in Xak-1 (song 10) that sounds to me as a clear demo by Micro Cabin from what their were proud that their driver could do. It's composed with only three instruments and all of them use the PSG as a 3rd operator do produce much more elaborated instrument waveforms than what was possible with the OPLL alone. You can notice that it's not just using the PSG to produce accords for the notes like Konami did with the PSG+SCC formula. The PSG channel is modulated with ADSR just as a lone carrier would have been, and with its timings carefully calculated to match the FM timings.

The result is a brass instrument with a metallic finish that is way more rich than the original OPLL instrument alone. And the PSG channel alone sounds like the notes are delayed.

For the 2nd instrument (*1) the difference is even more noticeable. Without the PSG "3rd operator", the OPLL instrument alone is shallow and lifeless, because a huge part of it is missing. And when the PSG channel is played alone it sounds like, well, a plain square wave.

*1: I don't know this instrument name, sorry. It plays high pitched notes on the song.

I made three recordings of this song for comparison. Please hear it in this sequence, since it enhances the perception of what went missing/got worse.

1) FS-A1ST with the audio fix. Notice how the instruments waveforms are rich and detailed

2) FS-A1ST with the original uncalibrated audio circuit. Notice how the details are washed out and the PSG channels are to loud to their respective OPLL channels, making the effect not that great and causing a gap in the middle of the trumpet. The whole sound is muffled and the global audio output level is also ridiculously low.

3) Standalone OPLL without the PSG. I recorded it from a real cartridge that has a separate audio output for the OPLL. This cartridge also has the FM lowpass filter fix. Notice how the two main instruments become rather poor and incomplete without the 3rd operator trick.

Regarding only the sound fix subject, I'll put some more before/after recordings online so people can check the sound quality difference.

By Grauw

Ascended (8457)

Аватар пользователя Grauw

20-08-2017, 00:38

Thanks for the comparison! I was hoping one would be posted Smile.

Gives nice insight in Micro Cabin’s techniques, especially the FM-only clip. That song is called To Town btw! (it plays a bit quick in your recording?) VGM pack here.

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