60fps Video Capture from Atari 2600 & Framemeister

[+ZeroPage Homebrew]

I currently capture gaming footage from my RGB modded light-sixer Atari 2600 through a Framemeister and into an Elgato HD60S and it works pretty well but it's definitely skipping/duplicating frames here and there for whatever reason. I upgraded a month or so ago from an Elgato HD60 to the HD60S and it works better but it's still not perfect.

 

A lot of homebrew 2600 games use flicker to multiplex the hardware limit of two 'sprites' on the same line at either 30Hz, 20Hz or even at the super flicker rate of 15Hz. If even one frame out of the 60Hz is missed this can lead to the player character or an enemy briefly disappearing making the recorded footage jumpy or even more flickery than it should be.

 

I'm fairly confident that the hardware wasn't made for capturing such precise footage and is more geared toward modern gaming or live video where a replicated/missing frame or two would be almost impossible to detect. Am I just misusing the hardware or is there a better hardware video capture device out there that's is better suited? Any ideas or suggestions? Thanks!!

 

Plenty of video examples on my YouTube Channel here: https://goo.gl/aPKSYy

[Mr SQL]

Cimmerian, here are three Atari games you can use to test your framemeister that use motion blur reduction technology which would make any frame stutter caused by the device very noticeable when/where it is occuring:

 

https://forums.blurbusters.com/viewtopic.php?f=7&t=4135&sid=37932989bfbdd45fcfa05bff3cf079f1

 

 

 

[Thomas Jentzsch]

I suppose its even worse, since some games don't display 60Hz. Some e.g. display 55Hz and some 65Hz. And YouTube probably makes it even more complex.

[Great Hierophant]

I was trying to capture Yar's Revenge off the Flashback 2 a couple of weeks ago and saw that at times, the whole barrier around the Qotile would simply disappear for several seconds, then go back to its flickering. I figured that was due to frame drops on my capture device. It wasn't worth capturing.

[+ZeroPage Homebrew]

Whoah, what? I thought the VCS and CRT televisions were locked in at 59.94Hz, how would a NTSC CRT display a 55Hz or 65Hz game?

Followup questions:

1) Is there a way to find out what frame rate a game is running at?

2) If a CRT is locked to 59.94Hz but not the VCS, how is it possible for the VCS to alter the number of times the screen is drawn per second on the CRT? I thought it was locked into the frequency of the AC power. Does the TV drop/repeat frames?

 

I suppose its even worse, since some games don't display 60Hz. Some e.g. display 55Hz and some 65Hz. And YouTube probably makes it even more complex.

[+ZeroPage Homebrew]

That's definitely similar to the issue that I'm experiencing.

 

Yar's Revenge appears to draw the Qotile barrier every alternating frame, every 1/60th of a second. It sounds like your capture device is dropping a large number of frames, every second one of them, making it appear like the barrier is gone. (quick, shoot it!)

 

Luckily mine is not QUITE as bad as that but it does appear to drop a frame every once in a while so that two "even" frames will show up together for a while making the screen appear 'stuck' for a very short period of time.

 

I was trying to capture Yar's Revenge off the Flashback 2 a couple of weeks ago and saw that at times, the whole barrier around the Qotile would simply disappear for several seconds, then go back to its flickering. I figured that was due to frame drops on my capture device. It wasn't worth capturing.

 

[Thomas Jentzsch]

No, TVs are not locked at a framerate, instead they are locked at a fixed scanline frequency (NTSC: 15,699Hz). With 262 scanlines this results into 59,9Hz, which is the NTSC frequency. If a game displays e.g. 280 scanlines, the framerate drops to 56.1Hz, and with 244 scanlines, you get 64.3 Hz. Most NTSC TVs can sync to those frequencies.

 

PAL uses about the same scanline frequency, but most PAL TVs have a wider framerate sync range (~45..65Hz).

 

Try Desert Falcon for a NTSC game which uses 280 scanlines. And there exists an Artillery Duel dump which only displays 241 scanlines.

 

To check the framerate, use Stella (ALT+L). Since 5.1 not only the current scanlines are displayed, but also the resulting framerate.

Edited June 14, 2018 by Thomas Jentzsch

[Great Hierophant]

The funny thing is that Yar's Revenge, according to this site, is outputting a bog-standard 262 lines :

 

http://www.digitpress.com/library/techdocs/vcs_scanlines.htm

 

The calculation for frame rate runs like this on an Atari 2600 : NTSC Colorburst (always 3579545) / # of Color Clocks Per Line (always 228) / Number of Scanlines Per Frame. So for 262 scanlines, the frame rate is 59.92Hz, and for 263 scanlines it is 59.69Hz and for 261 scanlines it is 60.15Hz.

[+ZeroPage Homebrew]

Ahh, okay. Very interesting, so the VCS dictates when the TV is to draw a new frame on the screen and can do so within a certain tolerance level.

Sorry but this next question probably delves into a programming question that has been gone over before ad-nausium. If I'm reading correctly, when the VCS sends a VSYNC, that is the signal to tell the television "hey get back up to the top, we're going to draw a new frame" and this can be done at any time whenever the programmer wants?

 

Now... The question is what the Framemeister, my video capture device (Elgato HD60S) and the capture software (OBS) are all doing along the line with 55-65Hz worth of framerates. Right at this moment they are all set to "60Hz" (whether or not this is actually exactly 60Hz or 59.94Hz shortened to 60Hz for simplicity is still remaining to be seen).

 

No, TVs are not locked at a framerate, instead they are locked at a fixed scanline frequency (NTSC: 15,699Hz). With 262 scanlines this results into 59,9Hz, which is the NTSC frequency. If a game displays e.g. 280 scanlines, the framerate drops to 56.1Hz, and with 244 scanlines, you get 64.3 Hz. Most NTSC TVs can sync to those frequencies.

 

[Thomas Jentzsch]

If they would do fixed 60 Hz, then either some frames would be skipped or displayed twice. Both causes flicker to look much worse than it actually is.

 

BTW: Have you noticed a difference regarding this between videos before and after uploading to YouTube?