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Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87183
03/25/13 12:11 PM
03/25/13 12:11 PM
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R. Belmont Online content
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Quoting machine/msx.c:

Code:
	/* key click */
	if ( BIT(m_port_c_old ^ data, 7) )
		m_dac->write_signed8(BIT(data, 7) ? 0x7f : 0);


If you take that at its word, it's toggling the DAC on keypresses (and if m_port_c_old is initialized the wrong way, probably at bootup) which will certainly make a popping sound.

Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87184
03/25/13 12:16 PM
03/25/13 12:16 PM
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Haze Offline
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does that code even belong in the driver/project? it looks like something along the lines of 'funky effects that should probably be in the OSD'

unless the real thing does that?

Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87185
03/25/13 12:47 PM
03/25/13 12:47 PM
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I assume since it's hanging off a PPI bit that hardware does that. But I really have no idea. Judge? smile

Incidentally, it's the only use of the DAC device I saw in the code. Maybe it's a model-specific feature that somehow got smeared across all the MSXes?

Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87190
03/25/13 02:36 PM
03/25/13 02:36 PM
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judge Offline
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The purpose for this code may actually be ok. I remember some setting where the machine would give produce click sounds when you were typing. Not sure if this implementation is ok though wink

Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87196
03/25/13 03:36 PM
03/25/13 03:36 PM
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The default behavior was that the keys would produce that "click" sound when pressed (at least, i remember it like that in my Canon V-20 and my friends' Sony HB-75P and Philips VG-8020). However, the sound posted by Dr.Venom in his first post is different to the "key pressed" sound, which is correct in the MESS MSX drivers that i have tested.

Re: Small (cosmetic) issue with MSX driver [Re: Dr.Venom] #87197
03/25/13 03:50 PM
03/25/13 03:50 PM
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Yes and no - because MAME/MESS lacks the analog backend you'd normally have on a DAC it causes a severe DC offset in the sound, which manifests as a pop when you start and stop audio. The "SPEAKER" device attempts to alleviate that, not always successfully.

Re: Small (cosmetic) issue with MSX driver [Re: R. Belmont] #87225
03/26/13 10:03 AM
03/26/13 10:03 AM
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Dr.Venom Offline OP
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I had to think a bit on what your "yes and no" meant, as I would tend to agree with Luengo that the "click" sounds when typing in MSX basic (which is normal hardware behaviour) seem correctly emulated in MESS.

To understand I created a mess -wavwrite capturing the boot-up and me typing "ZILOG INSIDE". See capture below.



The graph visually confirms your point; MESS clearly generates an inconvenient dc-offset, which is indeed the cause for the plopping sound that can be heard when starting/stopping audio, i.e. on driver boot-up and when pausing/unpausing the emulation. Incidently I found that this plopping sound is magnified to a greater extent (not "plop" but a louder "poing") when "Enable X-Fi Crystalizer" is set to ON on my Creative X-FI soundcard.

From your explanation I understand that the issue is caused by the lack of the analog backend of the DAC in MESS, and in effect it's not an MSX specific issue as such. Which could also explain why Haze noticed similar behaviour with some games in MAME.

Not saying it should be resolved, but since the "SPEAKER" device apparently should be alleviating this problem: is there, give this MSX case, possible room for improving the dc-offset normalizing routine of that device, or would it need another solution?

Re: Small (cosmetic) issue with MSX driver [Re: judge] #87306
03/28/13 07:00 PM
03/28/13 07:00 PM
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Dr.Venom Offline OP
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Originally Posted By judge
Knowledge regarding MSX/MSX2 isn't really a problem. Finding time is smile

That solves at least an important part of the equation smile

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