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"FM" speed tech question...
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dmichel
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Joined: 04 Apr 2002
Posts: 1167
Location: France

PostPosted: Sat May 11, 2002 11:11 pm    Post subject: Re: Oh... Reply with quote

Jabberwok wrote:
I see your point... a new ME core definitely sounds sweet Very Happy and kinda makes this whole tread useless then... Have any info on the ETA of this new core? or maybe this is a secret?


Yes, this is *top* secret. Wink
No infos yet, but don't expect it in the near future, I will have the time to release a few more betas before v1.0 is ready.

Quote:
im guessing that the 'infamous' screen stretch WILL be part of this new core hehehe....


We will have screen strectch before version 1.0. Smile
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David Michel
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David Shadoff
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Joined: 10 May 2002
Posts: 83
Location: Toronto, Ontario, Canada

PostPosted: Sun May 12, 2002 8:01 pm    Post subject: Re: "FM" speed tech question... Reply with quote

ethylene wrote:

Yeah, about the CD desynching. I had this, too, at one point, but don't anymore. I know that you are way more knowledgeable than most of us here, David, but still I'd like to suggest you try these settings:

    60 Hz refresh rate
    auto_frame_skip=y
    vsync=y
Does that help?


Actually it makes the problem much worse. In this mode, my Athlon 1.33GHz causes too many VSYNC interrupts, so the PSG music sequencer advances at about double speed.

Also, I like to have my monitor refresh around 72Hz, and i like to use the windowed mode. David's suggestion of adjusting the internal timer is perfect, but I don't know how/what to adjust internally...

My suggestion was based on the following information:
(a) exactly 60Hz is actually wrong. NTSC is 59.97 Hz
(b) internal timers in the PC are not reliable to this level of accuracy
(c) at a high level, the programmer is able to monitor how quickly the sound is drained from the DirectSound buffer, and is also able to count how many FPS are actually displayed (sometimes a frame is delayed slightly, or the timer is inaccurate). Fine-tuning adjustments can be made 2-3 times per second, to ensure that sound and motion are synchronized.

That's really all I meant to say.

- Dave

Amendment...
Actually, with the new code for Win2000/XP, this should become simpler, as I expect that the CDROM sound is ripped from the disc, and played as 44,100 Hz sound samples through DirectSound - and since we all know that there are 75 frames of CDDA audio per second, and 59.97 VBLANK periods, that we can count "virtual seconds" within each subsystem over certain timing periods, and ensure that they are kept in balance.

On the other hand, maybe the video subsystem of the PCE makes some kind of adjustment to the "59.97" VBlanks per second, based on the "vsync width", "# lines before frame", "# lines in frame", etc. measurements as defined to the VDC chip.

So, maybe it isn't too easy - but if anybody knows these technical details, David Michel does.
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Jabberwok
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Joined: 24 Apr 2002
Posts: 532
Location: Quebec, Canada

PostPosted: Mon May 13, 2002 2:39 am    Post subject: Omg... Reply with quote

Quote:
We will have screen strectch before version 1.0.


**Place drool here....** Very Happy

The new 1.0 core and screen stretch will place ME far from reach from the other PCE emulators... oh ya. This may be premature, but I smell perfection down the road Smile .
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