best cable for n-vi to sanyo plv-z3 projector

I hate to disagree with you Mike but I think you're attributing something to the nVi's analog output that isn't actually there. The difference between 480p from the digital output and 480p from the analog output is that the analog signal has simply been passed through a DAC. There's no 'processing' as such involved. I think the nub of the problem is in this statement here:

quote:

the quality of what the scaler has to work with is all down to whichever of the two units does a superior job of converting the digital picture info into an image waiting to go through the scaler

What do you mean by converting the digital picture into an image? The image is already there in digital form which is input directly into the scaler. There is no intermediate 'processing' step between the HDMI input and input into the scaler. If you think there is, what's that processing step called so I can go and look it up. Honestly, I'm not aware of it and if it's actually there I'd like to know what it is.

Finally, do you acknowledge that if you feed an analog signal into a projector/plasma/LCD display, that analog signal has to be converted back to digital again? In fact the point I'm making here is that if you do that conversion you are simply trying to get it back into the same format as if you'd sent the signal digitally to the projector via HDMI in the first place.

Alan, to deconstruct what you've just said....

1) The n-vi simply retrieves data from the DVD & sends it straight out of the DVI (if that's the port in use)

2) The screen/projector takes that feed & it goes straight to the scaler and appears as an image.

Hmmm....

If that's so, then why does a picture quality difference show it's face when I compare an n-Vi feeding DVI/HDMI YUV to my screen against a Denon 2930 feeding HDMI YUV to the same screen.

The screen's the same - so there has to be a difference in the quality of what's going into it... yes?


Absolutely I do accept that feeding analogue into a display does involve re-digitising it.

I'm not an electronics engineer, but I do know a bit about the n-Vi.... it absolutely DOES apply video processing to an image prior to it leaving via either DVI or Component terminals... for example one can adjust chrominance & saturation on the YUV output for either of these two connections.

I'll admit that I can't be certain that every display DOES process an incoming digital signal in any other way than scaling it.. but I do know that, for example, a number of high end projectors, like the C3X, have more than just a scaling technology on board.. more like fully fledged faroudja processor... which may well be why the C3X/DVD5 image was so impressive.


Fortunately the purpose of this thread was for gloop to ascertain what cable works best... he now seems to be in a postion to do a trial and see what works best for him.

My money's on component, and I've explained in great detail as to why.. but as long as anyone who reads this with a view to making the same decision then chooses to try both and select their own preference then I'm happy with that.

Thanks for querying my responses and getting the grey matter pulsating.. I enjoy a good think.

Mike

quote:

If that's so, then why does a picture quality difference show it's face when I compare an n-Vi feeding DVI/HDMI YUV to my screen against a Denon 2930 feeding HDMI YUV to the same screen.

Mike - The data from the disk isn't sent straight out of the DVI connector. The data has to go through MPEG decoding, de-interlacing and, like you mention, picture controls like contrast, brightness, etc. This explains why the digital output from the nVi can look different to the digital output from the Denon.

Ok, when it's been through these stages, the signal is still in the digital domain. At this point you can either send the digital signal out through the DVI connector or you can convert it to analog and output it on the analog connections.

On arrival at the projector, no doubt it goes through componentry that allows contrast brightness, etc to be adjusted but that's true regardless of whether the input was digital or analog, the difference being that the analog will need converting back to digital first.

From your earlier e-mail where you talk about converting the digital picture into an image - I think what you're referring to there is the picture controls, brightness, contrast and so on. This is all done in the digital domain, there's no actual 'conversion' as such from one format to another. Think of it like a digital volume control, you're simply altering numerical values. If this isn't what you meant by conversion from digital picture to image then please say so as I think this is the stumbling block in getting a common understanding.

No doubt in some situations analog component can look better than digital rgb as you've found and it's not the first time it's been said. My only concern was that the explanation you were giving seemed erroneous, or at least not as I understand it.

quote:

A: With compoment (analogue) cable connection:-

the N-vi; reads the dvd as a digital stream; uses its internal DAC to convert this to an analogue picture signal; passess the analogue picture signal to the component output and connected cable.

the screen; receives the incomming component analogue picture signals; uses its internal ADC to convert this to a digital picture stream; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.


B: With DVI/HDMI (digital) cable connection:-

the N-vi; reads the dvd as a digital stream; passess the digital signal to the DVI output and connected DVI/HDMI cable.

the screen; receives the incomming DVI/HDMI digital signals; uses its internal digital picture processor to convert this to a digital picture stream; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.

Accepting that I didn't specifically identify the circuitry that adjusts contrast, brightnes hue, saturation etc, it seems as if I need to delete the section highlighted below in bold?

quote:

A: With compoment (analogue) cable connection:-

the N-vi; reads the dvd as a digital stream; uses its internal DAC to convert this to an analogue picture signal; passess the analogue picture signal to the component output and connected cable.

the screen; receives the incomming component analogue picture signals; uses its internal ADC to convert this to a digital picture stream; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.


B: With DVI/HDMI (digital) cable connection:-

the N-vi; reads the dvd as a digital stream; passess the digital signal to the DVI output and connected DVI/HDMI cable.

the screen; receives the incomming DVI/HDMI digital signals; uses its internal digital picture processor to convert this to a digital picture stream; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.

Or am I still confused?

Cheers

Don

Don,

If I can summarise what Mike is saying, he's saying that there is a "digital stream to picture" conversion taking place on the analog output of the nVi that bypasses the equivalent convertor in the projector. The digital output of the nVi doesn't have this "digital stream to picture" conversion and so it gets done in the projector. So using your earlier post it should have looked like this:


A: With compoment (analogue) cable connection:-

the N-vi; reads the dvd as a digital stream; uses its internal digital stream processor to convert this to a digital picture; uses its internal DAC to convert this to an analogue picture signal; passess the analogue picture signal to the component output and connected cable.

the screen; receives the incomming component analogue picture signals; uses its internal ADC to convert this to a digital picture stream; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.


B: With DVI/HDMI (digital) cable connection:-

the N-vi; reads the dvd as a digital stream; passess the digital signal to the DVI output and connected DVI/HDMI cable.

the screen; receives the incomming DVI/HDMI digital signals; uses its internal digital stream processor to convert this to a digital picture; uses its internal scaler to convert this to 1080p; passess the 1080p picture stream to the plasma screen.


Mike, if I've misrepresented you or put words in your mouth please say. What I'm struggling to understand is what exactly this "digital stream to picture" converter is. At first I thought it might simply be a digital to analog converter, but that actually makes no sense as there is no digital to analog conversion step in the projector if it's being fed digitally (Mike - did you see Dave Dever's response to this?)

I thought it might be the picture control circuitry (i.e. for adjusting contrast, brightness, etc) but re-reading all this carefully I don't think you're referring to that at all. I'm going to make another guess here Mike; are you referring to the MPEG decoder (the bit that generates an uncompressed image based on the compressed image stored on the disc)? If so, regardless of whether you use digital or analog out, you will still be using the MPEG decoder built into the n-Vi, the projector doesn't have one. If I've still not got it, please can you describe what exactly this step is doing.

Don, I think if you delete the bits marked in bold above then you have the essentials of what is different between using the analog and digital outputs.

Gloop,

If you do the comparison and they look the same I'd suggest you go with HDMI. Why? because one day you may want to run a high definition source up to your projector. Analog component may look ok at 480p but will degrade at the higher frequencies required for HD.

I wouldn't bother with fancy expensive HDMI cables either. What you need is a good quality, well shielded 'studio' grade cable with tight fitting connectors and one that will work at the highest resolution+frequency you are likely to encounter. My recommendation is Molex. A 5m HDMI Molex cable will cost you about £30. I use a couple of 5m Molex cables here and even at 1080p60Hz they work perfectly.

The problem here is pretty straightforward.

One guy asks what cable he should use.

Another guy who's been down that road with the self same source component suggests a home dem of two options.

Nice & simple.

Folk start asking "why", and when "because I tried it, there was a difference, & I chose the best on performance" failed to satisfy the collective lust for knowledge, the guy making the recommendation made the horrendous mistake of trying to impart some technical details, but without making it so complex that folk got progressively (scanned!) more & more lost and confused.

I should have shut up at that point and just kept my fingers crossed that gloop took my suggestion and tried both cables.

Instead, I've embroiled myself in a situation where folk have been asking the same question again and again and again, and in an effort to simplify it I've then found myself on the sharp end from another fellow who questions the lack of precise technical detailing in my responses.

Yes I know what an MPEG decoder does, yes I know about colour space conversions, re-digitisation of analogue signals and all of that.
Allan... you're right that a display device doesn't necessarily have an MPEG decoder (although some which have SD memory card slots DO have them - so it's not an absolute). You're also right that not all display devices will do any more than upscale a digitally fed image... but SOME do.

It's this lack of absolutes in the destination component that absolutely warrants the necessity for the home dem.

Incidentally... I do agree with the future-proofing aspect of popping in an HDMI cable too... if gloop buys SKYHD or Virgin V+ his n-Vi will not video switch... and if the projector only has one HDMI or DVI socket then he will ABSOLUTELY need to use component to feed the n-Vi to it anyway.


Without going into another discussion Allan, I think you understand what I'm trying to get across, and I don't believe you're misrepresenting me. I've handed over (and freely, of my own will) too many hours of my life to this thread. I'm afraid I must bow out of this thread, safe in the knowledge that gloop will find what's right for him by home dem, but before the sheer frustration of having my words and help continually questioned leads me towards an ill-advised, frustrated, and un-gentlemanly response towards the next inquisitor.


All the best

Mike