HDMI NES

2015-04-22 03:58:14 pm

Since Kevtris is coming out with a mod kit for hdmi on the NES and Bunny is making an NES console with hdmi output, I was wondering what people thought of these as far as speedrunning goes. Do you think they will be accurate enough(i.e. no added delay) for speedrunning? Also, in general terms, is hdmi considered as good or better than RGB? If they're comparable then it would make getting quality NES captures much easier for people in the States that don't want to figure out all that's entailed with capturing RGB. Anyone have thoughts on either of these?

Thread title:

presjpolk

2015-04-22 04:36:54 pm

HELLO!

The nice thing about NESRGB is that it's using the original CPU and PPU, so it's really rare that something breaks (only game I've found that has issues with NESRGB is Arkista's Ring).

With this kit it'll be harder to say.

ahuynh

2015-04-22 05:22:25 pm

From a pure technical perspective, HDMI is a superior signal than RGB. This is because HDMI is a digital signal, and a digital signal will contain error correcting information. As a result, what you send is what you get. With analog signals, there will be degradation(static).

But in practice, it really doesn't make as much difference as you may think. Improper conversion from analog to digital is more noticeable than the static you get in an analog signal.

ConHuevos

Edit history:

ConHuevos: 2015-04-22 07:23:20 pm

ConHuevos: 2015-04-22 07:15:15 pm

2015-04-22 07:14:38 pm

Ciento Dos Huevos

Kevtris's HDMI NES modification will also be using the original PPU and CPU. Bunnyboy's NES will not, it will be a FPGA NES.

Keep in mind, both ignore a couple of cpu cycles in order to maintain exactly 60HZ for the HDMI timing. It's underclocked slightly. Roughly by 0.164166666667%. Unsure if this would affect a game such as SMB1 that gets measured in frames every time a new time is beaten or even RNG manipulation in some games from the cycles being skipped.

Crow!

2015-04-23 09:47:07 am

What's that gemma?

Is the CPU slowed down so the game runs at a slower frame rate, or does the HDMI display simply drop frames when it has to? The latter just means a lower quality recording (ironic given the supposed point of a HDMI output), while the former is generally unacceptable for speed runs.

presjpolk

Edit history:

presjpolk: 2015-04-23 11:33:54 am

2015-04-23 11:33:44 am

HELLO!

If they did drop the framerate of the game itself from 60.098 to 60, you're losing a bit over a second every 10 minutes, much as you do on Wii VC since there they dropped it to 60.002.

Slaughterhouserock

2015-04-23 12:58:07 pm

So it seems ok for casual play, but not as good as RGB/original hardware for speedrunning purposes. I was afraid that would be the case, but it's good to know it's a pretty minor time loss.

Thanks for the info guys! Still might try these out if they aren't too expensive.

ConHuevos

2015-04-23 03:54:21 pm

Ciento Dos Huevos

Quote from Crow!:

Is the CPU slowed down so the game runs at a slower frame rate, or does the HDMI display simply drop frames when it has to? The latter just means a lower quality recording (ironic given the supposed point of a HDMI output), while the former is generally unacceptable for speed runs.

Cycles are skipped on the CPU, it's not dropping frames.

Slaughterhouserock

2015-04-24 04:36:03 am

Quote from ConHuevos:

Cycles are skipped on the CPU, it's not dropping frames.

Excuse my ignorance, but what does that mean as far as gameplay is concerned? Framerates I understand, CPU cycles I don't.

ConHuevos

2015-04-24 12:53:12 pm

Ciento Dos Huevos

The NES is underclocked to maintain 60Hz rather than the normal 60.0985Hz. It effects it the same way PresJPolk mentioned.

presjpolk

2015-04-24 01:26:36 pm

HELLO!

Basically all the chips on the system are driven by a system clock, which is a rhythmic signal driven by a crystal.

The crystals installed in a standard NES that run the CPU and PPU cycle at about 21.5MHz, which then gets divided down to drive the CPU at 1.8MHz, and also drives the frame rate the PPU drives to 60.099 Hz.

What they do for the VC is, in emulation, reduce the emulated core clock speed, in order to get a frame rate of 60.002 Hz, but as a side effect reduces the CPU speed, and therefore the speed at which games go.

HDMI devices are expecting a standard framerate, so this HDMI kit will apparently have to do the same thing, only with actual hardware. So it all gets slowed down just slightly.

The result is that frame and pixel perfect tricks will be slightly easier to perform, but at the cost of losing roughly a second for every 10 minutes of gameplay, so for the most competitive games it's a huge handicap. 0.5s is pretty lethal for Super Mario Bros., but for some games you'd e just fine, which is why you see VC runners for some games.

Basically all the chips on the system are driven by a system clock, which is a rhythmic signal driven by a crystal.

The crystals installed in a standard NES that run the CPU and PPU cycle at about 21.5MHz, which then gets divided down to drive the CPU at 1.8MHz, and also drives the frame rate the PPU drives to 60.099 Hz.

What they do for the VC is, in emulation, reduce the emulated core clock speed, in order to get a frame rate of 60.002 Hz, but as a side effect reduces the CPU speed, and therefore the speed at which games go.

HDMI devices are expecting a standard framerate, so this HDMI kit will apparently have to do the same thing, only with actual hardware. So it all gets slowed down just slightly.

The result is that frame and pixel perfect tricks will be slightly easier to  perform, but at the cost of losing roughly a second for every 10 minutes of gameplay, so for the most competitive games it's a huge handicap.  0.5s is pretty lethal for Super Mario Bros., but for some games you'd e just fine, which is why you see VC runners for some games.

Slaughterhouserock

2015-04-24 01:29:24 pm

Thanks again!