Sound Errors in the most recent unofficial build, game-specific

[Former user]

Original [issue 37](https://code.google.com/p/genplus-gx/issues/detail?id=37) created by Icedus on 2009-08-08T05:26:45.000Z:

What steps will reproduce the problem? 1. Play Sonic 3 2. Get to Angel Island Zone 3. Play to the end of the level, and listen to the Airship sound

What is the expected output? What do you see instead? The airship sound has become static-y and just sounds wrong. Here is a video showing what it SHOULD sound like: http://www.youtube.com/watch?v=bvQhLCkLGSs (around 4:46; ignore the mis-colored Sonic...)

What version of the emulator are you using? r341

Please provide any additional information below (video settings, console region,...) This seems to persist no matter what I have any of the settings on. I didn't originally want to bring this up since this is a beta build, and you may have known about it, but I wanted to bring it to your attention just in case. Sorry if you already knew...

[Former user]

Comment # 1 originally posted by Icedus on 2009-08-08T09:33:15.000Z:

I'd like to add that it's not limited to that one particular sound, either. I went back and played more of the game, and there are pretty big errors in the crumbling platform and disappearing waterfall-platform sound effects, too.

[Former user]

Comment # 2 originally posted by ekeeke31 on 2009-08-09T09:30:24.000Z:

Thanks for pointing this out, these are indeed "hard to trackdown" issues as I don't have time to play through all games completely after each changes to the emulation core.

The first issue seems to be a problem with the new resampler I'm using (this is used to emulate the FM sound chip as its original frequency then convert it to our playback frequency), still not sure how to fix this, it's either a bug at certain sound frequencies with the resampler (which I didn't coded myself so it'd be hard to fix) or I'm using it incorrectly...

You can verify it's fixed by turning the "High Quality FM" option to OFF, in the Sound Settings menu, also it shouldn't happen with any versions below r327.

The problem with the platforms is another one though (the sound is like it is too short, right ?), I think it has always been there but I always thought this was the expected sound, even if it was weird. ALso, on the video you linked, it seems very similar to the emulator so I'm not sure it's really a bug .

Can you verify it also happens with the last official version (1.3.1) from the download page ?

[Former user]

Comment # 3 originally posted by Icedus on 2009-08-09T12:38:03.000Z:

Thanks for taking the time to address the previous issue. :)

I checked the same Airship sound today with the newest revision (r342) and the static sound is no longer present when High Quality FM is OFF. There is one minor thing I noticed, and that is when the airship drops a bomb, the hover sound seems to cut out for a second or so while the bomb sound effect plays. Throughout that scene, the hover sound should be constant, as heard in the video. (Maybe there was something wrong with the headphones I was wearing?)

What I meant by the platforms issue is, both of the platform sounds are more "harsh" than they are on the original hardware. The most recent official build (1.3.1) has the sounds much closer to what they should be, if not precisely.

In the case of the crumbling platforms, the "echo effect" is a little too loud and apparent in the newest unofficial build, where it should be quieter, but not gone entirely. I don't know how to accurately describe the issue with the platforms that disappear behind the waterfall, but you can see for yourself what I mean by the "steam" sound that plays when the platforms appear and disappear being a bit too harsh... if you compare the latest revision to the latest official build, while standing next to those platforms.

If I had to guess, this may caused by something similar to the reason the "echo effect" plays too loud with the crumbling platforms, but I have no idea about the technical aspects when it comes to this sort of thing, haha.

[Former user]

Comment # 4 originally posted by ekeeke31 on 2009-08-09T15:00:22.000Z:

the airship sound is still an issue because the High Quality FM option should provide the best sound emulation, so I'll have to fix it or revert to the previous resampler (which is slower though)

same thing with the platform sound being too harsh, if you tell me there are correct in the 1.3.1 version, it's probably something with the audio filtering

I think the hover sound cutting off is normal and happens on real hardware also (it's random however and happen when one channel is stealing another, in that case, I think it happens when Sonic jumps, the jump sound use the same channel as the hover sound). I might be wrong though, does it happens for you in the 1.3.1 version too, in similar condition ?

[Former user]

Comment # 5 originally posted by Icedus on 2009-08-09T15:56:02.000Z:

It seems you're right about the hover sound cutting off; I went back and tested it on the official and newest revision, and it hasn't happened since, both while running along and jumping occasionally. (I tested like four or five times in each case to be sure)

Thanks for the explanation as to why it happens though. I guess channels attempting to be used at once is the cause for the music to be cut in Sky Sanctuary Zone (present on real hardware) whenever you collect a ring? Interesting to finally find this stuff out, after so many years =P

Well, thanks for looking into this! The emulator has made fantastic progress. Keep up the good work. I'm sure you have the ability be able to figure out the resampler issue in due time. =)

[Former user]

Comment # 6 originally posted by ekeeke31 on 2009-08-09T16:16:35.000Z:

The static sound issue should be fixed now... strangely, it was due to the channel output limiters, using 15 bits (-16384;+16383) output like in 1.3.1 instead of 16 bits (-32768;32767) fixed this, not sure if this is correct or not though...

About the platform sounds being harsh, make sure filtering is enable (Low pass or 3-Band EQ), it usually cutoffs some frequencies and make the sound more "soft", like the real hardware would do (because of cheap analog components naturally "filtering" the sound output)

[Former user]

Comment # 8 originally posted by ekeeke31 on 2009-08-09T17:54:27.000Z:

really, High-Quality FM should be switched ON (you can for example compare the "end sign" spinning sound in Sonic 1 to see how it is more accurate when ON)

if you tell me the sound is still bad when it's ON, then it's definitively not fixed if you are talking about the sound being too harsh, it might require more stronger low pass filtering...

changing only the Low Freq value without changing the gain values should not change anything (it's a 3 band equalizer, meaning you have to configure each band, 1.0 is the default medium state and no band filtering is applied)

[Former user]

Comment # 9 originally posted by Icedus on 2009-08-09T18:26:00.000Z:

Okay, really sorry for the confusion up there, but you're right in saying that having it ON makes it sound better. I thought I had left it on OFF before obtaining the desired effect, but I went back to check and it was indeed on. The PSG and FM volume settings I had do seem right (Am I right in saying so?), although the Low Freq value thing seemed to be a placebo effect on my part. Regardless, I deleted that comment to avoid causing future confusion.

I don't think stronger filtering is required at this point, as the difference is pretty small. The only discrepancy is that the disappearing waterfall-platform sound effect is slightly higher pitched on actual hardware, but that's it. Everything else sounds good from what my ears can make out.

[Former user]

Comment # 10 originally posted by ekeeke31 on 2009-08-10T11:05:56.000Z:

ok, thanks for clearing that up

About the EQ, changing the low gain value will reduce/increase bass whereas changing the high value will reduce/increase treble. Changing the frequencies let you adjust the band width, but it's better to keep the default values if you don't know what you are doing and only play with the gain values to adjust the filtering (like you would do with an equalizer on your audio amplifier)

The difference in pitch might indeed be due to frequencies not being filtered exactly like the hardware is doing, which is why I added the configurable equalizer: the low pass filter is a simple fiter that will only "muffle" the sound and get ride of some high frequencies and might not act exactly as the real hardware.

The PSG/FM volume settings are only used to change relative level of both sound chips, you should keep the FM one to 1.0 and change the PSG one (from 1.0 to 5.0) to match the console output. On the real hardware, FM output is slightly lower than the PSG output and I found that a 1.5 ratio was pretty correct (you can use the first level music in Sonic 1 to do comparison if you want, it uses PSG sound as background "drum")

[Former user]

Comment # 11 originally posted by ekeeke31 on 2009-09-15T14:31:29.000Z: