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phaeron

Altirra 3.20 released

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Absolutely love the blue/white phosphor option. And the amber & green ones too. Very vintage and moody just like I played it decades ago in the backseat of the old chevy with the 9" B/W TV set!

 

One thing however is that the Star Raiders' shields don't "change color" or shades of whatever monochrome "color" it's set at. When I was a kid I'm fairly certain I remembered the screen becoming a bit foggy or hazy & lighter with the shields on and darker with them off. Do you think you can fix that up?

 

But, of course, when using the regular default color settings and palette or like the Atari 800 color palette, everything is fine. So definitely don't make any changes there.

 

Edited by Keatah

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I noticed that the reference indicator for the shield color disappears when in monochrome mode. Is that a bug? or by design? Or maybe just a result of circumstance?

 

 

221901587.png

221948074.png

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20 hours ago, Keatah said:

Absolutely love the blue/white phosphor option. And the amber & green ones too. Very vintage and moody just like I played it decades ago in the backseat of the old chevy with the 9" B/W TV set!

 

One thing however is that the Star Raiders' shields don't "change color" or shades of whatever monochrome "color" it's set at. When I was a kid I'm fairly certain I remembered the screen becoming a bit foggy or hazy & lighter with the shields on and darker with them off. Do you think you can fix that up?

 

But, of course, when using the regular default color settings and palette or like the Atari 800 color palette, everything is fine. So definitely don't make any changes there.

This is most likely bleed-through of the chroma signal. The chroma signal is pure AC and has no DC component, so it doesn't bias the luma, but I'm guessing it might have cause a visual brightness shift due to the gamma curve and the pattern, and also clipping at black. The Atari's signal also does not invert on lines or fields so it would have shown up as a stable pattern of vertical jailbars. I can probably emulate the brightness shift directly in the palette, more than that and the artifacting engine would have to be involved (though I need to hit that in order to fix unaccelerated scanlines anyway).

 

Who was it who caused me to open this particular can of worms again? Next you guys are going to ask for hum bars. I should start pretending that I don't know about some of these really old artifacts, that way I don't have to admit my own age.

 

12 hours ago, Keatah said:

I noticed that the reference indicator for the shield color disappears when in monochrome mode. Is that a bug? or by design? Or maybe just a result of circumstance?

Bug, happens when the color is pitch black and it doesn't update properly. Monochrome mapping makes it a lot more likely to occur. Fix queued.

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overly pronounced jail bars like we see today were not something a great monitor and appropriate cable or decent television produced, especially if any number of video modifications were done. The shields making the screen turn ever so slightly lighter (as you call haze or perhaps grey) was as it should be on a black and white tv or monochrome monitor.

most people on color sets or monitors saw the shields as blue or green tinge depending on calibration and tint of the computer or display...(some considered it a transparent blue or green tint of the view port)

Edited by _The Doctor__
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2 hours ago, phaeron said:

Who was it who caused me to open this particular can of worms again? Next you guys are going to ask for hum bars. I should start pretending that I don't know about some of these really old artifacts, that way I don't have to admit my own age.

I just want to add my +1 to my appreciation of adding these mono video modes, it's right up there with the other 'CRT like devolving' modes you've added to the video display.

 

I still have a really good memory of the 'vertical' venetian blind' effect of using the composite output on a monochrome monitor with color output... I don't recall if Luma 0 colors showed anything though.. But it seems it must have had to. It would be very nostalgic to see that emulated... not required, but it seems right up there with 'emulate what we remember seeing' haha.

 

Having a darndest time finding a picture of what the effect looked like online though. Maybe someone with a real mono CRT can show the effect of composite video being input?

 

Edit: Chroma subcarrier - thats the term I was looking for...

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1 hour ago, _The Doctor__ said:

overly pronounced jail bars like we see today were not something a great monitor and appropriate cable or decent television produced, especially if any number of video modifications were done. The shields making the screen turn ever so slightly lighter (as you call haze or perhaps grey) was as it should be on a black and white tv or monochrome monitor.

most people on color sets or monitors saw the shields as blue or green tinge depending on calibration and tint of the computer or display...(some considered it a transparent blue or green tint of the view port)

For a color monitor, sure, a higher quality cable and a monitor with better color separation would reduce or eliminate the jailbars. For a monochrome monitor, however, it's the opposite and the better your monitor was the more you saw them. Pretty sure you could easily see the chroma subcarrier on an Apple Monitor ///, because not only did it have enough clarity and bandwidth, that was the point -- it was designed for 80-column text and didn't do any luma/chroma separation.

 

The intensity of the artifacts would also have depended upon the computer model. The 800 has the weakest chroma signal, the 800XL in between, and the 130XE the strongest. Not sure about the 400, need to check that one.

 

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Just want to show my appreciation for these monitor modes, many on here love the super clear output that altirra gives and I also like those but I'm also a lover of 'how it was in the day' modes so really love the work that's gone in to recreating the nostalgia which for me is a key part of Altirra.

 

I for one am very glad you DO know about all this stuff and take your time to implement it into Altirra..

 

Thank you..

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1 hour ago, Mclaneinc said:

Just want to show my appreciation for these monitor modes, many on here love the super clear output that altirra gives and I also like those but I'm also a lover of 'how it was in the day' modes ...

Ditto. Super-sharp “perfect” modern displays have their places but for emulating stuff I had as a kid, or stuff I use today on real CRTs, these options make a tremendous improvement in emulating the entire user experience. So thank you! 

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Yeah, same thing if you use the artifacting modes....Just one of those things..

 

Btw Avery / anyone else, what do you think of this 'Run Ahead' area of programming for emulators?

 

Nice video by Byuu, author of the fabulous Bsnes / Higan emulator explaining the way it works..

 

 

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On 9/30/2019 at 3:37 AM, ldelsarte said:

For the stereo/mono, it's just that I'm often surprised at the computer with my headphones, when I was doing something else and then I play my old favourite Atari games; suddenly all sounds are in L only. I go to my sound card settings and change that. I was hoping to find in Altirra, maybe, a drop down menu option, easily accessible to route L to both L & R for simplicity.

There is a drop-down menu option. But no keyboard shortcut. Disabling stereo outputs mono to L+R.

Altirra-Stereo.png

Edited by Nezgar
Department of redundancy department.

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If it doesn’t introduce differences between the way the original system and emulated system look, then great.

 

But it looks like it needs tweaking on a per-game basis. So meh..

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The real question is what does real hardware do? It should do what that does. If real hardware takes 1, 2 or 3 frames to register a button, then the emulator should too. 

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The stereo option hasn't been in the menu for a while, it's now in Configure System. Everything in either can be bound or unbound to custom keyboard shortcuts.

 

It's not possible to render the same way as the original hardware because of differing output paradigms. In the original hardware configurations, anything done by the CPU immediately affects the video output, which is scanned out a scanline at a time and displayed immediately by the CRT. There is essentially zero lag inherent in the system and for most games about half a frame of input lag due to sampling input at vertical blank.

 

In modern systems, there are a number of sources of delay, including:

  • Input delay. Keyboards can have 20-50ms delay from physical key down to USB message. Gamepads have some delay as well.
  • Frame render delay, as the entire frame has to be generated instead of being scanned out as it is generated. This can be done more quickly than the CRT scanout, though, but it means that the CPU and display are generated faster than real time -- which means that any input that would have happened mid-frame is missed and not seen by the emulated program until one frame later.
  • Frame synchronization delay. The Atari refresh rate is slightly off from 50/60Hz, and additionally PC refresh rates are often off from even that (40Hz, 75Hz). This adds another half a frame of latency on average.
  • Compositor delay. When running in windowed mode, the display compositor typically adds another frame of delay. In Windows, this happens because the DWM uses the worst possible time to composite, immediately after vblank, with the frame then not beginning scan-out until after the next vblank. Altirra then has to conservatively start far enough behind vblank to ensure that it renders its frame in time for the DWM to pick it up, about half a frame behind vblank -- which basically guarantees 1.5 frames of delay here.

Recent versions of 3.90-test have the frame timing changed to throttle the emulation at scanline 248 instead of 0, which reduces input latency by up to one frame. DirectX 11 mode on Windows 8.1 or later is also generally one frame better due to DXGI waitable latency object support. Still, end-to-end latency is still several frames higher than what you would get with the real hardware on a CRT.

 

Run-ahead attempts to reduce this by correcting the emulation after the fact, by rewinding the emulation state to what you were seeing at the time of the input event and re-simulating forward. It cannot truly reduce latency, but helps improve timing precision of inputs -- which still helps as while you can't press buttons 60 times a second, you can still press buttons with 1/60th second precision. For N frames of run ahead, you still can't see the first N frames resulting from your input, and it makes the emulator N times slower because it has to re-simulate that many frames each time.

 

The most complex requirement of run ahead, though, is the need to be able to perfectly snapshot and roll back the simulation. Altirra has a lot of internal state due to everything it emulates, and still doesn't have save state support for a lot of devices. For those that it does have, not everything is a simple save-restore as some states like clocks need to always run forward and require rebiasing. Disk images currently can't be rolled back, external network connections can't be rolled back, UI displays like printer output can be rolled back but are messy to do so. For these reasons, Altirra won't be supporting run-ahead any time soon.

 

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Thanks for the answer Avery, was interested in your thoughts on it, Altirra does everything I want and 100% more but alternative looks at how things can get done are always interesting to explore, so thank you for looking at it and the in depth explanation....

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Update:

http://www.virtualdub.org/beta/Altirra-3.90-test14.zip

http://www.virtualdub.org/beta/Altirra-3.90-test14-src.zip

  • Monochrome colors are now brightened when color is present, based on linear blending of the peak signals (clamped y-c and y+c).
  • Monochrome modes now work with high artifacting. Luma/chroma filters and PAL blending are disabled, so this shows the raw chroma signal instead.
  • Fixed a double-init issue in the audio code that was slowing down startup.
  • Fixed representative color table UI not updating properly in monochrome modes.
  • Fixed a crash with SoundBoard at $D600 or $D700 when either the ANTIC display list or playfield was pointed at SoundBoard's hardware registers.

 

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Wow. Thankyou phaeron, with this release you've hit a major nostalgia spot for me... This amber mono + high artifacting mode seems pretty much bang on to what I remember my dads Zenith mono monitor looking like with a composite input... It was this mode on this monitor that gave me a sense of 'how colour was made' in the video signal being able to see the chroma subcarrier like that... Of course, using the grey colours (POKE 710,0 through 15) always looked best and smooth, or just using the luma output from the computer most of the time. So it had (has) some educational value as well.

 

Hats off...

Amber-Chroma1.jpg

Amber-Chroma2.jpg

Amber-Chroma3.png

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Yes!  Big nostalgia hit!  Star Raiders as I first played it! ... I didn't realize the shields tinted the screen blue until I purchased a colour TV!

668226328_MonoStarRaiders.thumb.png.4fbdbd7888203e7551eb8610a6ecd8db.png

 

Thank you phaeron!

 

 

(On a related note, growing up with only a black and white TV meant that I never understood the joke about Star Trek's red-shirts 🙂 )

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10 hours ago, Nezgar said:

Wow. Thankyou phaeron, with this release you've hit a major nostalgia spot for me... This amber mono + high artifacting mode seems pretty much bang on to what I remember my dads Zenith mono monitor looking like with a composite input... It was this mode on this monitor that gave me a sense of 'how colour was made' in the video signal being able to see the chroma subcarrier like that... Of course, using the grey colours (POKE 710,0 through 15) always looked best and smooth, or just using the luma output from the computer most of the time. So it had (has) some educational value as well.

Yes, thank you SO MUCH for these new features.

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3 hours ago, Caterpiggle said:

How do that in monochrome (amber) screen above in self-test mode ?? Guide me how. I did tried to find that feature in new update Altirra 3.90 test 14 ??

System > Configure System > Video > Monitor mode > Monochrome (amber phosphor) and System > Configure System > Video > Artifacting mode > NTSC/PAL high artifacting (auto-switch).

 

If you want the curvature, System > Configure System > Emulator > Display > Hardware acceleration > Use hardware acceleration for screen effects, then View > Adjust screen effects > Horizontal/vertical distortion.

 

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Also, make sure VBXE output is not being used, else you will just get regular colour.

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