Prism component vs OEM component cables for Gamecube

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RebeL9
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Prism component vs OEM component cables for Gamecube

Post by RebeL9 »

The Prism component cables have been out for a few months but I still haven’t seen an in-depth comparison with Nintendo’s OEM cables. Have anyone here compares these cables?
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kitty666cats
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Re: Prism component vs OEM component cables for Gamecube

Post by kitty666cats »

I remember hearing several people had issues with no audio from the things, never heard any complaints about video.

If I had a GameCube I’d personally get one of the HDMI adapters - that way I’d have the option of chaining a HDMI to component or HDMI to VGA after it & have a wider compatibility range and all those cool menu features! Just need a DAC that one is sure passes 480i & 240p (which many do)
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

kitty666cats wrote:I remember hearing several people had issues with no audio from the things, never heard any complaints about video.
You didn't hear complaints about video because they're the same old issues with GCVideo Lite.
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

Here's the rundown.
  • This product is identical to the Bitfunx/Kaico GameCube Component Cable, as it is made by Bitfunx.
  • The video output is 15% darker than normal. This is because the original GCVideo Lite design only output the proper range in RGB mode.
  • Chroma is output as if the sample location was on the right. (delayed by one pixel)
  • When the picture is transmitted as Cr-first, Cb is shifted right and Cr is shifted left.
  • Chroma has linear upsampling. While this is great for GameCube games with a 4:4:4 video processor, it's not optimal for most other cases.
  • There is no reconstruction filter. 540p/1080i will appear as if nearest-neighbor scaling was applied on the horizontal axis with a fractional ratio.
  • The audio output has a bug where half the samples are dropped and the channels are swapped. (24kHz effective sample rate)
McNutts
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Re: Prism component vs OEM component cables for Gamecube

Post by McNutts »

While I don’t have an in depth technical knowledge of these cables as some people have on this board I do own the HDMI adapter from Retro Bit and the prism cables on the way since I bought a Retro Tink 5x a few days ago.

The HDMI adapter is great. The picture is much sharper than I get with any cheap solution from my Wii.

The only issue I have had with the HDMI adapter for the GC is that some times the picture drops out for a half second when the resolution switches like when I’m playing Eternal Darkness.

When I get the Prism component cables I will reply back here with my impressions compared to the HDMI adapter from Retro Bit.

If there is anything you would like me to try out for you just ask and I’ll do my best.

My Equipment:

1x65” LG C8 OLED
1x55” TCL 55P605
1x36” Sharp CRT with component and S-Video inputs
Retro Tink 5X
GameCube with Pi Pico mod, HDMI and Component connections from Retro Bit
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

McNutts wrote:While I don’t have an in depth technical knowledge of these cables as some people have on this board I do own the HDMI adapter from Retro Bit and the prism cables on the way since I bought a Retro Tink 5x a few days ago.
Just get a Portta HDMI to YPbPr converter. You'll still have the sync drop issues from GCVideo-DVI v3.0+, but it's vastly better value than this e-waste.
McNutts wrote:The only issue I have had with the HDMI adapter for the GC is that some times the picture drops out for a half second when the resolution switches like when I’m playing Eternal Darkness.
Update to GCVideo-DVI v3.1 to solve this problem with this game, or turn on "Force Video Active" in Swiss.
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Einzelherz
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Re: Prism component vs OEM component cables for Gamecube

Post by Einzelherz »

Why was GCvideo added to the component cable? Is it just to sell more "features"?

I genuinely like retro bit stuff, even if it's not perfect. I also take what Extrems writes pretty serously, even if I only understand half of it.

Aside from the 15% darkening, what kind of... real world issues would one see? Using displays ranging from consumer and pro CRTs to HDTVs and even upscalers?
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

GCVideo Lite does the minimum needed to translate the Rec. 656-derivative interface into something a basic video DAC like the ADV7125 can use. It also provide a S/PDIF interface, which Bitfunx bafflingly chose to use even though there's I²S available.
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DragonQuarter
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Re: Prism component vs OEM component cables for Gamecube

Post by DragonQuarter »

If I don't understand a majority of the issues with the Prism cables...am I fine to use them? :wink:

I also have a Carby HDMI. Is that considered better?
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

I stopped using analog video since GCVideo-DVI v3.0pre1 came out. I prefer the CARBY over the others as it pose no mechanical conflict with the Analog AV Out (I still use analog audio out of convenience) and it's an officially supported board target.
DragonQuarter wrote:If I don't understand a majority of the issues with the Prism cables...am I fine to use them? :wink:
If you use Game Boy Interface, you should at minimum avoid its audio output unless you want to be ear-raped by the excessive aliasing. You'll need to use a third-party cable with a narrower plug for it to fit.
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

Here's your stupid ~real world examples~ using the RetroTINK-5X Pro on firmware 2.73 with default settings.

Retro-Bit Retro Prism Component Cable
Image

Nintendo GameCube Component Video Cable
Image

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable
Image

Retro-Bit Retro Prism Component Cable
Image

Nintendo GameCube Component Video Cable
Image

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable
Image

Please refer to these sections for more scientific analyses:
https://www.gc-forever.com/wiki/index.php?title=Audio_quality_tests
https://www.gc-forever.com/wiki/index.php?title=Game_Boy_Interface/Standard_Edition#Video_quality_.28480i.2Fp.29
https://www.gc-forever.com/wiki/index.php?title=Game_Boy_Interface/High-Fidelity_Edition#Video_quality_.28360p.29
https://www.gc-forever.com/wiki/index.php?title=Game_Boy_Interface/High-Fidelity_Edition#Video_quality_.281080i.29
RebeL9
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Re: Prism component vs OEM component cables for Gamecube

Post by RebeL9 »

Thanks for comparison pics. What is noticeable here is the slight darkness on retro bit cable
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kitty666cats
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Re: Prism component vs OEM component cables for Gamecube

Post by kitty666cats »

Extrems, do you have a HDMI to VGA you prefer? I made a thread about a nice HDMI to VGA + YPbPr two-in-one unit, I highly recommend it. Properly passes through full range RGB!
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

I haven't really looked at those and the one I happen to have has a very hot output.
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WobblingPixels
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Re: Prism component vs OEM component cables for Gamecube

Post by WobblingPixels »

I am kinda suprised that the GCVideo + Portta combo provides the sharper image than Nintendos component cable looking at the images. :shock:
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

The Nintendo GameCube Component Video Cable is set up with a 480p low-pass filter (240p/480i is approximated with linear interpolation) while the Portta HDMI to YPbPr Converter is set up with a 720p/1080i low-pass filter.

This difference only matter when you're oversampling the signal, and doesn't matter when using optimal sampling, although auto-phase detection will have an easier time with the latter.
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WobblingPixels
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Re: Prism component vs OEM component cables for Gamecube

Post by WobblingPixels »

Extrems wrote:The Nintendo GameCube Component Video Cable is set up with a 480p low-pass filter (240p/480i is approximated with linear interpolation) while the Portta HDMI to YPbPr Converter is set up with a 720p/1080i low-pass filter.

This difference only matter when you're oversampling the signal, and doesn't matter when using optimal sampling, although auto-phase detection will have an easier time with the latter.
Thanks. I appreciate your work.
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aphexacid
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Re: Prism component vs OEM component cables for Gamecube

Post by aphexacid »

I have the prism component cables as well as the prism hdmi adapter. I was floored when I saw the picture from the hdmi adapter. I had official component cables back in the day, but sold them. Tried my Gamecube with my ossc and RT5X (old firmware still though). Right away the darker picture stood out. And no where near as sharp as the hdmi adapter.

I’m perfectly happy with the adapter. And I just installed a picboot last week. Fantastic stuff going on here.

Grateful to to Extrems, and all the other boys and girls in the community that give us these great gifts that allow us to wax on about micro pixels.

Cheers!
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Rulumi
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Re: Prism component vs OEM component cables for Gamecube

Post by Rulumi »

That does seem to have quite some chroma shift on it.
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Einzelherz
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Re: Prism component vs OEM component cables for Gamecube

Post by Einzelherz »

TY for the excellent comparison photos, Extrems!

I assume the HDMI adapter doesn't suffer from the same issues? Or did I significantly misread your explanation?
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

The Portta HDMI to YPbPr Converter has other issues.
  • RGB-F is the only usable input format. RGB-L and YC444 aren't handled properly, and YC422 isn't supported. This means rounding errors and clipping of illegal colors.
  • 540p/1080i doesn't work unless the horizontal sync pulse width is set to one sample, which is silly and causes display compatibility problems.
  • It's a slowpoke to video timing changes.
  • The audio output goes to sleep during silence, and takes a few milliseconds to ramp back up.
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NewSchoolBoxer
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Re: Prism component vs OEM component cables for Gamecube

Post by NewSchoolBoxer »

Say I want to buy an NTSC GameCube. If cable cost is of no concern, which analog output Component cable should I buy? No modding solution.
Does every cable work on stock NTSC and PAL consoles? While Component sits outside of NTSC vs PAL, 480p sync timings derive from NTSC and 576p from PAL.

I'm aware thanks to Extrems' site that several of the newer cables give better video than the expensive and rare Nintendo one.
Extrems wrote:This product is identical to the Bitfunx/Kaico GameCube Component Cable, as it is made by Bitfunx.
...
The audio output has a bug where half the samples are dropped and the channels are swapped. (24kHz effective sample rate)
That's ridiculous. Caps audio at 12 kHz. YouTube videos and FM radio go to 15 kHz.

Is what is really needed, is someone to fix the GCVideo Lite firmware? Is GCVideo meant for mods only? Same author, why are there two projects?
GCVideo Lite GitHub wrote:Why did you use that weird Video-DAC, it's a non-stock part at Digikey!
It wasn't when I designed the board some months ago... Instead it was the cheapest 24-bit video DAC available.
Seems like an amazing lack of foresight. No one else came along to do anything better so can say is unfair to criticize the originator of all the non-Nintendo Component cables, at least the ones that pull from the digital out versus less optimally transcode the RGB on PAL.
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Unseen
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Re: Prism component vs OEM component cables for Gamecube

Post by Unseen »

Extrems wrote:It also provide a S/PDIF interface, which Bitfunx bafflingly chose to use even though there's I²S available.
Many I2S DACs need an extra clock signal, typically 128 or 256 times the sample rate, which is not directly available from the Gamecube - decoding SPDIF was probably their way around that.
NewSchoolBoxer wrote:Same author, why are there two projects?
Why wouldn't there be two projects? GCVideo Lite was the original one because it's much simpler to just convert the data and throw it at a DAC, GCVideo-DVI came later. Since I have no use for an analog output when I can use digital instead and since Lattice's "your license key is node-locked and only valid for a year" stuff is pretty annoying I stopped updating GCVideo Lite pretty soon and it looks like nobody cared enough to submit a pull request to fix any issues with it either.
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aphexacid
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Re: Prism component vs OEM component cables for Gamecube

Post by aphexacid »

Anyone know of a av multi cable that can sit side by side with the prism cable? The stock av cable and prism component cable do work, but the bodies kind of force each other in the opposite direction. Can he good. They definitely don’t sit like the official Nintendo cable does that’s for sure.
I wouldn’t mind trying it out.
Maybe filing dow the av cable a bit too if you really wanted to.
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

I know a generic S-Video cable and the HD Retrovision SNES Component Cable will fit.
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NewSchoolBoxer
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Re: Prism component vs OEM component cables for Gamecube

Post by NewSchoolBoxer »

Unseen wrote:
NewSchoolBoxer wrote:Same author, why are there two projects?
Why wouldn't there be two projects? GCVideo Lite was the original one because it's much simpler to just convert the data and throw it at a DAC, GCVideo-DVI came later. Since I have no use for an analog output when I can use digital instead and since Lattice's "your license key is node-locked and only valid for a year" stuff is pretty annoying I stopped updating GCVideo Lite pretty soon and it looks like nobody cared enough to submit a pull request to fix any issues with it either.
Thanks for explaining. I went back and read the GitHub descriptions and I understand now. I'm sorry I was somewhat snide. I didn't know you were a member of the forum. I looked up the DAC specs. Much better than I expected except for the crosstalk / interchannel separation.

Is cost of Lattice key holding you back or have your interests have shifted by now? I get the general idea that FPGA tool chain is far from ideal or open sourced. Pluto-IIx boards are in stock, unlike everyone's Cyclone and Xilinx projects. RS-232 serial port interface surprised me but if it's what you know, it's what you know. I'm decent at assembly for microprocessor programming. Doesn't mean I can succeed at FPGA but I'm jealous enough of its DSP ability that I'm willing to try.

Is a shame GitHub only has one other contributor. I don't know how popular Pluto-IIx is compared to others. PIC programming was forced upon me in college so I was relieved to find it widely used and understood IRL.

I have to ask, would ideal Component video be better than ideal RGB video on GameCube since the native format is YCbCr? Since Extrems mentions (I think) some games with 4:4:4 encoding, is YCbCr locked to 4:2:2? Is the greater interpretation here that Nintendo cable and GCVideo Component upsample to 4:4:4, meaning those games could look better in RGB? Naturally this was in era where many LCDs and Plasmas had no 4:4:4 support.

I saw a comment that Nintendo used a very impressive DAC but I couldn't find any details.
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Unseen
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Re: Prism component vs OEM component cables for Gamecube

Post by Unseen »

NewSchoolBoxer wrote:Is cost of Lattice key holding you back or have your interests have shifted by now?
It's not the cost - the Lattice toolchain is free to use. The annoying part is to have to update the license file again and again because it is node-locked and time-limited - a paid version would not help because as far as I know it would still be node-locked. Also, as I mentioned I have little to no use for an analog output when I can have digital instead - though I was tempted to build a bitstream for existing boards that generates composite video as an april fools release.
RS-232 serial port interface surprised me but if it's what you know, it's what you know.
I have used that interface only once, to check if it would work for documentation purposes - for actual development I just used JTAG because that is well-supported and I have the interface(s) for it.
I'm decent at assembly for microprocessor programming. Doesn't mean I can succeed at FPGA but I'm jealous enough of its DSP ability that I'm willing to try.
That will probably help less that you expect. ;) Even though the code looks like linear procedures with control flow and sometimes even loops, that is deceptive - in an FPGA everything is parallel and (usually) nothing happens until the next clock pulse.
Since Extrems mentions (I think) some games with 4:4:4 encoding, is YCbCr locked to 4:2:2?
The Gamecube cannot output a real 4:4:4 signal, the video bus signal is always 4:2:2. extrems talk about 4:4:4 video from a Gamecube is deliberate misdirection, the actual signal is still 4:2:2 but each pair of pixels has the same color. With a non-standard conversion to analog this can look the same as an analog 4:4:4 signal with halved horizontal resolution, but in the digital domain it clearly not a 4:4:4 signal.
Is the greater interpretation here that Nintendo cable and GCVideo Component upsample to 4:4:4, meaning those games could look better in RGB?
I think the Nintendo cable uses sime kind chroma upsampling, but I never had the opportunity to measure it. Technically it has to do something because simple replication of the first pixel color for the second pixel introduces a slight chroma shift, but I'm not sure if that would be visible on a typical display - in a digital output it is visible if you know what to look for.

GCVideo just uses basic linear interpolation for the non-co-sited pixels - there are algorithms that claim to provide better sharpness, but they are more complicated and the FPGA resources are strictly limited.
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Extrems
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Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

Unseen wrote:I think the Nintendo cable uses sime kind chroma upsampling, but I never had the opportunity to measure it. Technically it has to do something because simple replication of the first pixel color for the second pixel introduces a slight chroma shift, but I'm not sure if that would be visible on a typical display - in a digital output it is visible if you know what to look for.
If the evidence isn't strong enough for replication, the datasheet is out there now.

Image

I found this method to be sharper with 4:2:2 video decoders, as you'd find in a TV.
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aphexacid
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Re: Prism component vs OEM component cables for Gamecube

Post by aphexacid »

Extrems wrote:I know a generic S-Video cable and the HD Retrovision SNES Component Cable will fit.
Got this cheapo cable off Amazon. Significantly more narrow than the Nintendo av cable head. Now they can live in harmony. I don’t even need this method at all, I just like having an added option.

It’s this one:
Gam3Gear SNES Nintendo N64 Gamecube S Video Cable https://a.co/d/bc5gaQQ
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PixelPhoenix
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Re: Prism component vs OEM component cables for Gamecube

Post by PixelPhoenix »

Even if it's only a pixel, that's a noticeable chroma shift.

I didn't pick these cables up when they released (I'm still using Carby component, which has its own issues with its inability to output 360p on GBI, as those were based on GCVideo-DVI v2.4d-2), but it makes me thankful for what I already have.
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