CPCWiki forum

General Category => Emulators => Topic started by: cpcitor on 01:09, 25 May 21

Title: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 01:09, 25 May 21
TL;DR summary:
* In practice most current machines, PC, Android, etc have 60Hz, which cannot render smooth scrolling at 50Hz.
* A CPC prod perfectly synced at 50Hz will not look good on a 60Hz screen.
* But a real hardware CPC can output 60Hz, so a CPC prod can be perfectly synced at 60fps! 
* For real-CPC based execution, it's easier+cheaper to plug a simple cable from CPC to a 60Hz monitor than find a monitor supporting 50Hz or buy an adaptor that kills the smoothness and picture quality.
* The only missing part of this puzzle is this: to ease working on 60fps prod on the CPC, wish more CPC emulators support emulating a 60Hz monitor.
* Bonus: realistic rendering of effects like RetroVirtualMachine "beam" can become possible.

Or "why caprice32 has the image below right and how this is related to 60fps/60Hz display":





People implementing an emulator might be interested in the analysis that follows.

Motivation

1. Show demos with perfectly smooth rendering.

This is only possible by mapping one CPC frame to one output frame. This is easy when framerates are close. 50.04Hz of the CPC is close to 50Hz. Frames can be played in sync and audio/video sync will not drift much quickly. This is not close to 60Hz which is current standard. This means either audio/video drift, or duplicating frames several times per second. I took this approach (one-to-one frame mapping) on the 60Hz YouTube rendering of 2021 a CPC Odyssey by cpcitor & The Other Days :: pou√ęt.net (https://www.pouet.net/prod.php?which=89060) because after the music starts, audio/video sync can drift wildly without it being a problem. This required manual adjustment and won't fit most prods in general!

Which means... to support 60fps video files on the web we can... work on hardware CPC with a 60Hz screen. Easier development environment is: support 60Hz on CPC emulators!

2. Support 60Hz on CPC emulators.

The CPC hardware and firmware supports 60Hz. A real CPC can be connected to a TV (even a recent one, provided it has analog input) through an analog cable and produce 60Hz that can be decoded. Even a PC monitor can do the job with a custom CPC-to-VGA cable. Few monitors support 50Hz through VGA because it is out of standard. With a CPC at 60Hz most monitor can accept that.

If an emulator supports a CPC configured for 60Hz, then prods can offer a 50/60Hz toggle and finally be rendered perfectly on modern displays and on video platforms (like YouTube).

This is now new: I remember in 1993 seeing a game on Atari ST where pressing space toggled between 50Hz and 60Hz display. The analog monitor adjusted, and the aspect ratio changed since there were less lines in the 60Hz mode

First thoughts about how emulator could support 50 and 60hz

This is highly technical and could very well go over the head of many readers, that's okay. Faithful emulation of the CPC monitor is similar to capturing analog video, and this is complicated. This video is interesting on the topic https://www.youtube.com/watch?v=2a9E6Cx8Hgw . (One can guess that I worked in a company making video products that supported analog and digital output, with a high bar on excellent output quality and never missing a frame.)

CRTC = the chip that generates signals, including hsync and vsync
CRT = the tube-based monitor, the circuitry that senses hsync and vsync and tries to fit that to its expectation to drive an electron beam on a zigzag to the front of the tube.

We could concentrate on the CRTC output directly:

* "horizontal event": every time a horizontal CRTC counter says so, it triggers a hsync, that's a new line and we continue plotting pixels in the emulator's framebuffer on the next line on the left
* "vertical event": every time a vertical CRTC counter says so, it triggers a new vsync, that's is a new frame and the emulator spits a new frame and continues plotting pixels back to top of the framebuffer.

Questions:

* What happens when the time between two "event" is not close to the monitors expectations (1/15625s horizontal, 20ms vertical)?
* The signal is sometimes in steady state (identical time between hsync and vsync), with definite stable fps, but at times it is not.

Not answering these questions prevents from faithfully emulating a number of situations.

A basic emulator would have currently crude solutions to this (like, a hsync or vsync is the event to consider), but will this be enough to render all prods?
To their defense I would say: different CRTs react differently, so most prod avoid it, although some demos use it.

Conclusion: a faithful emulation of 50Hz/60Hz and some demos benefits from a CRT model.

Adding a CRT model and considering the signal downstream

What's a CRT model?  It's an answer to "what to do when facing early, late or absent hsync/vsync signals from the emulated CRTC?".

CRT behavior

Monitors of the era adapted to a few missing or extra lines (a.k.a vsync happening a little too early or late) without much noticeable visually. This means slight deviations from the theoretical framerate were just obeyed without problem.

Facing unexpected (or absent) hsync/vsync signals, CRT behavior is this: the CRT "hunts" for the signal.

* Unexpected horizontal timing results in generating a horizontal beam return at an "arbitrary" time. Visually this causes possibly wild slants of vertical lines into diagonals, with pixel or even subpixel horizontal shifts.
* Unexpected vertical timing results in generating a vertical beam return at "arbitrary" time. Visually this causes possibly wild "rolling" of the picture up or down.

Notice that when the monitor is "rolling", it does refresh the screen repeatedly but at a different framerate, depending on the monitor, so not 50Hz not 60Hz, something even different.

So, what about 50Hz vs. 60Hz then?

Hunting is when CRT could not catch the vsync in the expected time slot. The "expected time slot" is dependent on 50Hz/60Hz monitor devices. Notice that a GT-65 monitor with its "vertical sync" knob fits this model if you think of the knob as "manual adjust of expected delay between two vsync".

In practice, a 50/60Hz bi-sync CRT model would solve our goals.

How to do that in an emulator: adjust the expected time slot for the vsync signal so that a 50Hz vsync interval is recognized, a 60Hz vsync interval is also recognized, and depending on the case, the vertical line density (lines per inch) is adjusted.

Great! So, supporting 60Hz in an emulator can be simple! Now, what about fine timing details?

My current setup has 3 screens with respectively 60.03 59.95 and 50.01 Hz. This means that a program cannot generate a highly realistic rendering when not knowing on which screen it is, or even worse when its window spans multiple monitors. This means this corner case has to be "delegated to downstream" (not trying to handle it oneself).


There are two use cases:
* targetting interactive use on a PC desktop, possibly multimonitor, or a video capture to a modern format (MPEG family)
* targetting demo with perfectly smooth scrolling on a rigid platform with exact known framerate, or full-screen rendering on a monitor with known characteristics (think Raspberry Pi on a HDMI TV)

Timing option "Free": The first use case is well suited to formalizing with "free timing" of every frame. This fits the MPEG model of video streams: every frame in MPEG comes with a PTS "Presentation TimeStamp". The emulator would generate images (stable or rolling) and whenever its emulated CRT model would command the electron beam to fly back (stable or rolling), it would spit the frames as they come (using SDL API or any other, like FFMPEG), with PTS information if the API supports. This is "simple" and the best solution when running on a desktop environment or unknown framerate downstream equipment. When you get a "refresh-on-demand" screen on your desktop, you'll want this.

Timing option "Fixed": assume a display framerate, like the one of the HDMI TV connected to the Pi, or the fixed framerate expected by the target video platform. Emulate what the CRT monitor would display, and spit frames at the exact rate required downstream. This is formally sound. It does not match current multi-screen setup. It implies a specific step, somethings to do when the "ideal, free" timestamps are far from the fixed rhythm. That's where extremely realistic emulation becomes possible.

Indeed, the problem we face with timing option "fixed" is very similar to filming the virtual CRT with a camera. This is interesting as it allows a level of realism that no other option can provide. One can fade pixels depending on the exact time the electron beam passed on it ("remanence effect"). This is the "beam effect" RetroVirtualMachine has been faking because its emulation model does not allow to reproduce if faithfully. With this option "fixed", the actual beam effect could be emulated accurately! It would also emulate the exact reason why filming an actual original CPC screen with a modern camera or smartphone yields awful results. But being emulated this can be tweaked at will: for example, one can define an emulated remanence profile. This reminds me how some professional cameras have had for the last 20 years a button to lock to an external monitor just by aiming at it and pressing a button: they would film the scene normally, but that screen would be perfectly stable, removing all flicker and beam artifacts. Once you get there it's relatively simple to do. This is what we can do in emulation.

Summary

That was tough! To summarize:

* It is possible for CPC prods to support 50 and 60 fps output. 50Hz for original CRT, 60Hz for VGA screens not supporting 50Hz, for TVs, for Youtube and other online platforms.
* Hardware-wise, 60fps prods that render perfectly on Youtube without a hack are possible with a real CPC and an analog video capture card (google for "VGA capture").
* Emlulator-wise, the CRT model and discussion above allows emulators to support CPC prods targetting 60 fps output.

Test criteria for emulator support of 60fps

* See if emulator offers an explicit or implicit 60Hz option. If explicit, enable it. Some emulator may detect 60Hz automatically.
* Configure emulated CPC to output a 60Hz signal.
* See if image is stable.
* See if emulated video stream indeed spits 60 frames every second.

Quick experiment

Trying to hack an emulator to switch from 50 to 60Hz (or from "#define FRAME_PERIOD_MS 20.0" which would be 16.666ms but that gets truncated to 16, oh gosh) very much depends on how the emulator is organized. It's very easy to mix up 20ms as basic block for an arbitrary "abstract time frame" and 20ms as an actual output framerate. No success so far.

* Arnoldemu WIP: supports 50/60Hz option in menu which toggles LK4 which has firmware do the right thing! But arnoldemu isn't updated and difficult to compile nowadays. Actual FPS not measured.
* https://floooh.github.io/tiny8bit/ : stable image. Actual FPS not measured.
* Caprice 32: image rolls. No clean success on hacking the source code.
* cpcec 32: image rolls. No clean success on hacking the source code.

Unknown:

* Winape: can you tell here?
* Others: can you tell here?

Other quick experiments

Cpcec and caprice32 both react well to : out &bc00,9 : out &bd00,3 . This generated two images 320x100 stacked and not one 320x100 image at 100Hz. Supporting 60Hz implies more flexibility.

cpcec does not emulate the slanting, it just snaps the next line to the steady state position, something no CRT of the era does.
caprice32 emulates the slanting.




Details about 60Hz on original CPC hardware.

The CPC *can* produce a 60Hz video output, by programming the CRTC to switch to a new frame after fewer than the 312.5 lines of PAL timing. This is seldom discussed, e.g. on https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/60hz-cpc/msg4856/#msg4856

Even the stock firmware in ROM supports 60Hz! To be more precise, at CPC reset, first bytes of ROM sets mode 1 then sets CRTC registers for 50 or 60Hz depending on a wire on the motherboard. This is explained in sections 12 and 13 of official firmware guide, see http://www.cpcwiki.eu/index.php/Soft968:_CPC_464/664/6128_Firmware .

In BASIC it is as easy to activate as:

Code: [Select]
out &bc00,4 : out bd00, &1f     # (0x1F+1)*8 lines = 256
out &bc00,7 : out bd00, &1b    # Adjust vertical position

# ROM does this:
out &bc00,5 : out bd00, &6      # +6 = 262.   15625Hz (line frequency) / 262 = 59.63Hz
# firmware documentation says it should have been 4
out &bc00,5 : out bd00, &4      # +4 = 260.   15625Hz (line frequency) / 260 = 60.096Hz

But although 60Hz CPC were made and sold in the US, this is seldom known.

See ROM disassembly by @arnoldemu (https://www.cpcwiki.eu/forum/index.php?action=profile;u=122) at http://cpctech.cpc-live.com/docs/os.asm lines 1435-1477:

Code: [Select]
;----------------------------------------------------------------
; RST 0 - LOW: RESET ENTRY
0000 01897f    ld      bc,$7f89 ; select mode 1, disable upper rom, enable lower rom
0003 ed49      out     (c),c ; select mode and rom configuration
0005 c39105    jp      $0591

(...)

0591 f3        di     
0592 0182f7    ld      bc,$f782
0595 ed49      out     (c),c

0597 0100f4    ld      bc,$f400 ;; initialise PPI port A data
059a ed49      out     (c),c

059c 0100f6    ld      bc,$f600 ;; initialise PPI port C data
;; - select keyboard line 0
;; - PSG control inactive
;; - cassette motor off
;; - cassette write data "0"
059f ed49      out     (c),c ;; set PPI port C data

05a1 017fef    ld      bc,$ef7f
05a4 ed49      out     (c),c

05a6 06f5      ld      b,$f5 ;; PPI port B inputs
05a8 ed78      in      a,(c)
05aa e610      and     $10
05ac 21d505    ld      hl,$05d5 ;; end of CRTC data for 50Hz display
05af 2003      jr      nz,$05b4         
05b1 21e505    ld      hl,$05e5 ;; end of CRTC data for 60Hz display

;; initialise display
;; starting with register 15, then down to 0
05b4 010fbc    ld      bc,$bc0f
05b7 ed49      out     (c),c ; select CRTC register
05b9 2b        dec     hl
05ba 7e        ld      a,(hl) ; get data from table
05bb 04        inc     b
05bc ed79      out     (c),a ; write data to selected CRTC register
05be 05        dec     b
05bf 0d        dec     c
05c0 f2b705    jp      p,$05b7

;; continue with setup...
05c3 1820      jr      $05e5            ; (+$20)

;; CRTC data for 50Hz display
05c5 defb &3f, &28, &2e, &8e, &26, &00, &19, &1e, &00, &07, &00,&00,&30,&00,&c0,&00
;; CRTC data for 60Hz display
05d5 defb &3f, &28, &2e, &8e, &1f, &06, &19, &1b, &00, &07, &00,&00,&30,&00,&c0,&00
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: roudoudou on 09:10, 25 May 21
As MANY CPC productions are neither 50Hz nor 60Hz, maybe a free-sync support?
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 10:40, 25 May 21
As MANY CPC productions are neither 50Hz nor 60Hz, maybe a free-sync support?

Hi @roudoudou (https://www.cpcwiki.eu/forum/index.php?action=profile;u=1714) . Do you mean "neither *exactly* 50 or 60Hz"? Or do you mean they commited to more important deviations?

Can you give examples and elaborate?
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: roudoudou on 11:25, 25 May 21
The Abduction of Oscar Z, 20350 nops between each frame in the menu => 49.14Hz
Examples are numerous
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: TotO on 11:49, 25 May 21
Well...

If you really want to display the CPC correctly in an emulator, you just have to either display in 100Hz (like SugarBox does) or use a screen that supports 50Hz, and there are a lot of them in LCD, whether it is TV or PC monitors. Youtube can display 50Hz recording too. The problem is not just the frequency but the visual rendering anyway, and an LCD will probably never display CPC as well as a CRT.

Why we have to make 60Hz on a machine, which will therefore penalize users of real CPCs, to have to turn the dial behind their CTM each time it is necessary to change frequencies, to please people who use and program for emulators... We walk on the head.

Most PCs and other tablets / smartphones will be freeSync in the near future, so it's a sword in the water. As a reminder, running a program at 60Hz also means reducing the number of scanlines to display to keep the same machine time per frame.

Finally, if you want to see what 60Hz gives in a game on CPC, just launch Pac-Man Emulator which allows to toggle between 50Hz/60Hz by pressing SPACE from the service menu (TAB).
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 14:56, 25 May 21
The Abduction of Oscar Z, 20350 nops between each frame in the menu => 49.14Hz
Examples are numerous

Ok, so there are numerous examples of prods not *exactly* 50 or 60Hz, but they are pretty close, like borrowing a fraction of percent.

These are small deviations to the PAL timings, BTW the default screen does not exactly conform to PAL timings either because it would imply 312.5 lines. A CPC could do that by changing the vertical adjust every frame or using the interlace register of CRTC. Something similar is discussed on https://www.cpcwiki.eu/forum/programming/interlace-demo-maybe-464-only/msg18896/#msg18896 .

Anyway, this shows that virtually all CPC prods stuck to whatever the original CRT could display without rolling. In practice this meant "don't mess with hsync interval more than advancing/delaying a few milliseconds, a.k.a. keep 15625 lines per second" and "ensure the total line number is close to 312, which is roughly equivalent to sticking to 50Hz".

This totally makes sense and even I am reluctant to walk away from anything that the original 464 or 6128 with an original monitor can do. Making a 60Hz output is one thing that is considered here.
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 00:33, 26 May 21
Well...

If you really want to display the CPC correctly in an emulator, you just have to either display in 100Hz (like SugarBox does)

Thanks, didn't know that one. It works on Linux but was not listed in Linux section of https://www.cpcwiki.eu/index.php/Emulators . I just updated the wiki.

Youtube can display 50Hz recording too.

Do you mean that on your machine Youtube changes your screen refresh rate to 50Hz when you watch a 50fps video? I never saw that anywhere. Not on my PCs, not on Android smartphone.

Why we have to make 60Hz on a machine, which will therefore penalize users of real CPCs, to have to turn the dial behind their CTM each time it is necessary to change frequencies, to please people who use and program for emulators... We walk on the head.

With current state, CPC prods are penalized when incorporated in a video stream (especially online parties). Working on a perfectly smooth scrolltext and showing a jerky scrolltext to the audience feels pointless. That is being penalized.

With target state, no one is penalized. I mentioned in parent post doing 50/60Hz compatible prods. With this option, a prod can be perfect on a real CPC and perfect on online streams.

Most PCs and other tablets / smartphones will be freeSync in the near future, so it's a sword in the water.

Things are not so simple. What you say would only cover the "interactive desktop" option in parent post, not the online streaming cases.

As a reminder, running a program at 60Hz also means reducing the number of scanlines to display to keep the same machine time per frame.

I explained that in parent post. You get 5/6 of the usual cycle count. That's just part of the deal.

Less workpower on each frame, more frames per second.

Ambitious prods like 3D word (Starion, Elite, Starglider, 3D starstrike) allow several frames anyway, which averages. So the raw computing power per second is the same, you don't lose anything.

Even better: on top of this equivalence, there's an extra property in favor of 60Hz. If the monitor adjusts line density, you cover more area with less lines, so you can animate with 5/6 the amount of bytes to cover.

So, all in all I think that 60Hz is a +20% performance win.


Finally, if you want to see what 60Hz gives in a game on CPC, just launch Pac-Man Emulator which allows to toggle between 50Hz/60Hz by pressing SPACE from the service menu (TAB).

Interesting find. I tested, indeed it does. The top lines are cropped as a result.
How did you get to know that?
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: TotO on 11:49, 26 May 21
@cpcitor (https://www.cpcwiki.eu/forum/index.php?action=profile;u=531) : I mean that Youtube allow to have 50Hz video recorded since some times. I can imagine that if you are in full screen, the refresh rate can match if the monitor support 50/100Hz display, may be not. ;D

OK, may be I have not well understood. Doing compatible 50/60Hz prod will not deserve the 50Hz productions, penalised by the requirement to display more frame and less lines for the 60Hz version and probably require more work. Typically, the problem is known since 35 years ago with the video game systems running worst on the 50Hz consoles while it can be better if dedicated for them (more CPU time, more DMA time, mode scanline displayed, ...).

About Pac-Man Emulator, I know that because I have worked on the project, around 10 years ago. ;D
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: eto on 18:50, 26 May 21
Would switching to 60Hz really change anything? Or would it just affect other people? I mean, 60Hz is not really a standard that everybody but CPC uses. People watching it on a TV will most likely have a 50Hz refresh rate and would then experience a similar problem. Or those that are using gaming monitors with 144 or 165Hz. I remember that when I had a CRT that 72Hz was a thing.

How big is the disadvantage for a CPC production? I guess on the other machines that have been common in Europe, we will also see many 50Hz releases. Or am I mistaken here and they are all running on 60Hz?[size=78%] [/size]

I also quickly checked the displays that I have at home. The displays with HDMI offer a 50Hz mode. So if I WANT to see a production without any stutter on emulation, I can simply switch to a 50Hz mode. And the VGA screens that I have connected to real hardware through a GBS8200 with GBScontrol in line doubling mode also accept 50Hz.


Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: Lone on 19:16, 26 May 21
From what I studied about this subject, the sync to screen frame is not the only problem we have.


In my first attempts, I though that we can approximate 50.04 hz to 50 hz. So, I tried to sync with frame. Screen is perfectly smooth, scrollers are really similar to what a CPC does for example. But....
But we get some sound glitch as we sometimes miss a sample , producing a cracking sound. So, not convincing.


Best guess for emulation, is to use GSync/FreeSync, and synchronize with sound : Sound is always good (so, no sound cracking or anything), and GSync doest the trick (not tested with FreeSync as I don"t own a FreeSync monitor. Guess what, I got my GSync screen just to test those behaviour (and eventually keep it because it's quite convincing).


My attempts are correct for windows (even better than the 100hz-with-black-screen-insertion, because of the perfect sound).





Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: roudoudou on 19:29, 26 May 21
freesync/gsync is the obvious solution for emulator. It's not to CPC coders to do the job

for youtube video, this must be a player problem, not an upload problem

Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 22:10, 26 May 21
freesync/gsync is the obvious solution for emulator. It's not to CPC coders to do the job

for youtube video, this must be a player problem, not an upload problem

Go fix Youtube, then. :P It will be easy to ensure that all players on all platforms that access youtube (web browsers, Android app, iPhone app, various appliances that have dedicated Youtube client), they all become 50Hz capable.

(Ironically, embedded clients like Kodi on Raspberry Pi may probably already play videos from Youtube in 50Hz on capable screens, as Popcorn Hour devices could.)

More seriously, as written in my too long first post of this thread, there are different use cases:
*Interactive desktop case is best with Freesync clearly.
* 50Hz on youtube is fine if viewer is savvy enough to adjust their screen to 50Hz, which is not always.
* When a party streams on twitch, the video stream is the same for everyone and it is 60fps, period. Party organizers and attendants have seen prods butchered before.

I'm not saying that I like this state, just that a prod for a party that features smooth motion must run smooth. Mechanically, in this case the prod must support 60Hz.
Failure to grap this just results in prods looking jerky compared to other 8bit machines that natively do 60fps and produces a poor impression of the CPC compared to other 8bit machines.
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: eto on 12:49, 27 May 21
Failure to grap this just results in prods looking jerky compared to other 8bit machines that natively do 60fps and produces a poor impression of the CPC compared to other 8bit machines.

Which European 8Bit or even 16Bit does by default do 60fps? The C64 (afaik) can't switch between 50 and 60Hz without a hardware mod so probably most European demo releases are running at 50Hz. I did a quick Google check on 20 Amiga 500, Archimedes, ST and C64 demos and almost every (except for 1) official demo video on Youtube was recorded at 50Hz.

Quote
Mechanically, in this case the prod must support 60Hz.

Youtube supports 50Hz, also Twitch does. It's a matter of if you CARE to make the right settings. Youtube e.g. recommends to upload videos with the frequency of the original source and if you check the official demo videos on Youtube you will see, that they mostly are recorded at  720p@50 or 1080p@50Hz. There is probably a good reason for this. And all of them have the same "disadvantage" on a 60Hz screen. If a party streams at 60Hz all 50Hz releases on all systems are penalised. And that includes all game consoles released in Europe.

50Hz is a problem for those that can't switch and/or don't care to switch to 50Hz. If you care about the 50Hz problem, you can fix it. But if you would switch every demo release to 60Hz you would penalise those that care most: the people with original hardware. I really don't want to adjust the monitor every time, just because otherwise I can't run the demo. I would probably simply not do it - maybe unless it's mind blowing. But 20% less cpu cycles per frame might not be the best guarantee to get something mind blowing. So with a switch to 60Hz we would end up with less impressive demos that are optimised for people that don't care anyway.
Title: Re: Wish 60Hz/60fps support in emulators. Thought on emulating a CRT.
Post by: cpcitor on 14:40, 27 May 21
Quote
I really don't want to adjust the monitor every time, just because otherwise I can't run the demo. I would probably simply not do it - maybe unless it's mind blowing. But 20% less cpu cycles per frame might not be the best guarantee to get something mind blowing. So with a switch to 60Hz we would end up with less impressive demos that are optimised for people that don't care anyway.

This is not what I'm talking about, has already been brought in before and I already explained in previous posts. Repeating: I never pushed to writing anything that would not run on original hardware or need a change. A proper CPC prod must run primarily on the original CRT monitor which does not support 60Hz. What I did is invite modern prods to offer a 60Hz variant. 60Hz variant actually lowers the Z80 effort as explained above.

The interesting thing I will keep:

Quote
Youtube supports 50Hz, also Twitch does. It's a matter of if you CARE to make the right settings.

When I mention the framerate at the latest party, the organizers did not consider the stream could be 50Hz on twitch, that the stream would be 60Hz, mentioned at least one other party where streaming was 60Hz and 50Hz prods were "butchered", no choice. I'll ask them again if they can change that for next time. Thanks for the tip.


Quote
Youtube e.g. recommends to upload videos with the frequency of the original source and if you check the official demo videos on Youtube you will see, that they mostly are recorded at  720p@50 or 1080p@50Hz. There is probably a good reason for this.

Of course: for the selected people (including you and I apparently) that see and appreciate the difference and are capable of setting up their local screen with true 50Hz (or 100Hz), the original 50fps stream of a real 50fps prod is the only true way. When I watch an Amiga demo on Youtube, I pay attention to the stream fps, choosing a high quality capture and render it on a 50Hz-capable screen tuned to 50Hz. Quality often requires effort.