Understanding video signals

Hi Gary,


A few comments:


>* S-video. A huge improvement over composite, but still has some

>compromises. Not good enough for HD or probably even 480p DVD.


Yes and S-Video has one further disadvantage: Since Y/C are on

seperate cables, you have to painfully be aware that different

cable lengths will introduce a delay within Y & C which will degrade

your PQ.


>This seems to usually refer to YCbCr or YPbPr (same thing??),


Basically yes.One refers to progressive and the other to interlaced.

I don't recall which is which tho


>but NOT RGBHV. High quality signal transfer. I believe this is the native

>data format for DVDs, though I don't know why they chose it instead of

>RGB.


Simply a question of $$$. Using pure RGB would mean that you couldn't

fit a film on a single DVD.


>your projector only takes RGBHV (which many do) then you need RGBHV.


Once again: Any PJ MUST convert to RGB at some time in the video

chain as there are only R G B output devices (tubes).



>Some also use RGB with sync on green,


This is written RGsB


>or RGBH/V (?) with one sync line.


This is written RGBs


So you can easily identify what the PJ supports.


> This requires expensive (usually >$500) or low-quality transcoders.


Correct. You don't want to skimp on a transcoder since it is directly

"fooling" around with your PQ.


>* VGA. Used to feed computer monitors, but I believe it contains RGBHV

>signals on some of its pins? So if you have a VGA output you could use it


YES from a compatability standpoint. NO from the electrical driving

capabilities of the output stage. A VGA card was never meant to drive

a parasitic capacitive load (your long video lines).


>* DVI-I and DVI-A. I'm not clear on the difference.


No, they are called DVD-D and DVD-I. DVD-D ONLY contains the digital

signals, whereas DVD-I has BOTH analog & digital. Most of the analog

signals are in the seperate 5 pin "subsection" of the connector.


> DVI-I can also easily be converted to VGA or RGBHV.


No. DVD-I CONTAINS analog RGBHV, so there is no conversion

necessary.


> Are there any other cables I should run to the projector mount while the

> walls are open?


That depends on the PJ and your wishes An Electrohome can be

controlled via RS-232. You can also save your internal PJ settings via

RS-232 (I added this line to my runs) If you will be running a switcher,

and wish to control the switcher (if possible!) via the PJ remote, you'll

need another cable. IF you ever plan on adding an additional input

board to your PJ, you'll need more cables. If you have a motorized

screen and want to control it via the PJ: another cable Here is a

brief list of what I have running through the walls:


- RS-232

- S-Video*

- Composite*

- RGBHV #1

- RGBHV #2


* are just for quick connects of standard equipment. I don't plan on

getting PQ through these ;o)) OBTW: I'm running a 8500 (later Ultra).


>play any SD sources (VHS tapes or cable/OTA signals), you'll also need a

> doubler / deinterlacer / scaler.


Yes, this is one point where I'm still deciding on I have it narrowed

down to:


1. Cinemateq Picture Optimizer Plus

2. IScan HD

3. CenterStage CS-2


From here it gets harder to decide. All of the above will require an

additional switcher for my case as they only have one RGBHV output

(and I need two)


> The Momitsu handles this for DVDs, but you can't feed other signals into

> it for scaling, since it does all its work with the digital DVD signal.


Correct. If/when I get one of the video processors above I will be

testing the Momi via DVI-D to compare PQ to the internal scaler.


>Cheapest scaler I know of is the TVone XGA theater, which scales up to

> 1024x768 for $149. I have no idea what its quality is, but you'd be

> feeding it fairly low-quality signals anyway.


While I don't know the above I DID buy a cheapo scaler similar to

that one about 10 months ago. It SUCKS. Its just sitting in its box

and collecting dust until I pawn it off on ebay.


>already shelled out for, you also need to drop another $500-1000 on

> a transcoder and scaler? Plus maybe a switcher of some kind?


Yes (double that figure roughly) and DONT forget the screen, either.


Greets,

Reinhard

Yow. Danke, Reinhard, that's a great and helpful response. Mostly not what I wanted to hear, though. :-(

Quote:
!? I thought S-video was a one-cable solution. I've never actually used it so I didn't know.

Quote:
Good point. So even if your PJ has component in, it still has to be converted to RGB. Would avoid the need for a separate transcoder, though.

Quote:
Hm. Even a 16' run, I suppose? Belden says 1505a has 16.3pF/ft so that run would have only 261 pF. Doesn't seem like that horrible a load, but I'm no expert.

Quote:
You obviously have a different budget than I do. I doubt I'll even get a transcoder anytime soon because it's more than I can spend now. Maybe if/when I get HD satellite. I may go with the TVone scaler because it's cheap and I've heard it's decent. Which was the one you bought that you didn't like? My standards may be lower than yours.


Gary

Hi Gary,


>Danke, Reinhard, that's a great and helpful response. Mostly not

> what I wanted to hear, though. :-(


Sorry.


>!? I thought S-video was a one-cable solution. I've never actually used

> it so I didn't know.


The short interconnection between HiFi components usually IS a one

cable solution using 4 conductors inside (2 hot, 2 ground). However,

longer runs and PJs usually don't use the Hosiden connector, but rather

BNC, which forces the use of two independant cables. If you route the

two cables BEFORE you put on the connectors you may end up with

different lengths of cable, which inserts a delay in one of the lines (and

wrecks havoc the the PJs signal processing). What I wanted to say is if

you use S-Video just make sure the cable length is the same.


>Good point. So even if your PJ has component in, it still has to be

>converted to RGB. Would avoid the need for a separate transcoder,

>though.


Yes/No It really depends on how good the internal YUV to RGB

transcoder is. Within a PJ I always tend to believe the manufacturer

wants to add some extras, but can't drive the price up, so they have

to make it cheaper. A stand alone transcoder or video processors is

designed to do it's job without having to sacrifice quality (at least that

would be what one should expect).


>Hm. Even a 16' run, I suppose? Belden says 1505a has 16.3pF/ft so

> that run would have only 261 pF. Doesn't seem like that horrible a

> load, but I'm no expert.


Hmm. 16 ft is on the edge. You might get away with it, tho. If it's not

too much trouble try a short run of the same cable vs the 16 ft run and

see if there is a difference. (I mean before you install it in the walls of

course).


BTW: if you are deciding on whether or not to get the Momitsu. I would

say go for it. It is a bit soft on 720p or 1080i, but it MOST definately is

a great bang for the buck. And eventhough it is a low dollar DVD player,

Momitsu is doing a great job of implementing bug fixes and improvements

in the firmware and that's something a lot of high end maufacturers don't

even think about. bblue just posted a couple of mods on the Momi a few

days ago, which make perfect sense to me (he adds a few caps to various

places to decouple the PSU) and since the Momi has found such a wide

attraction to a lot of CRTers, there will be more mods and info available

in the future.


>You obviously have a different budget than I do.


No, not really. My income is around $25k per year, so I'm not that

rich (and I have a lot of other hobbies), but I do scrounge around

in order not to pay more than I have to


>anytime soon because it's more than I can spend now.


Actually its the same here, but us freaks will do almost anything for

our HTs The advantage of a video processor is not only does it

offer a lot of adjustments, but it also functions as a switcher.


> Maybe if/when I get HD satellite. I may go with the TVone scaler

> because it's cheap and I've heard it's decent. Which was the one

> you bought that you didn't like?


It's called DigiVISON DV-800. It has a OTA TV tuner, 1 composite in 1

S-Video in and a VGA passthrough. Even the passthrough degrades

video quality. The quality of the Momi has TONS better. I haven't given

the box a second glance (which means I haven't opened it up to see

whats inside and that means a lot in my case )


> My standards may be lower than yours.


Hmm, I don't know, but the more you progress, the hungrier you get.


Greets,

Reinhard

No, I don't really use it.


I plan on using it with an ECP for the boys... I'll have to do a quick comparison to see if their $200 DVD/VCR/5.1 speaker combo with s-video run into the TVone XGA Theater scaled to 800x600 or 1024x768 is better/easier than my Coby 480p DVD set-top box. Even though I haven't hooked up my TVone in 3-4 months, I seem to recall it looked better than 480p from my Coby 480p experiments a few weeks ago. Plus the TVone will allow them to scale their PS2.


But I like this Momitsu so much, that I suspect I'll buy the next generation when it comes out and roll this V880 to them, and I'll probably set them up with the VPH1271.


Since I'm not getting anywhere with my power problem on one of my 1031's, I'll hook up my TVone and give it an updated assessment. I'll also use it with my 20' RGBHV cable. Although I've learned my lesson with cheap VGA->RGBHV and I'm switching everything in my new HT to thick BNCs.


-Clarence

Don't waste your Xtra plugging S-video into it. The ONLY way to connect to it is via RGBHV.


Video is like watching through venetian blinds.


If you watch composite/s-video sources, then get a cheap scaler, or a capture card in a PC.


One little correction, s-video is not "Not good enough for HD or probably even 480p DVD.", it is incapable of handling these signals.



RGBHV

RGBHV

RGBHV

RGBHV

RGBHV

RGBHV


Got that? ;-)

OK, I reaffirmed my positive assessment of my $120 TVOne XGA Theater...


I went straight for the worst case scenario:

- Cheap APEX DVD set top box (actually VHS VCR would be worst case)

- I found a 6' composite cable which is thin enough to floss my teeth with.

- I used my longest (20') VGA-RGBHV cable

- ran it to my Marquee at 12' wide


It's better than watchable. And it's definitely better than the Coby 480p.


It'd make a good tutorial on what to look for in good vs bad sources/connections in a video chain.


But if I brought my wife down here and did an A/B comparison, she'd say she couldn't tell a difference. So I'd point a few details and noise artifacts out to her, she'd acknowledge the difference, but roll her eyes and say "normal people wouldn't notice or care". Yeah, but we never claimed to be normal.


Gary, this XGA box is worth trying.


In fact, if you really wanted to get cute, it could server as your remote switcher...


VCR -> composite input into XGA Theater

PS2 -> s-video input into XGA Theater

Momitsu -> VGA passthrough input into XGA Theater

There's even an antenna input for TV tuner.


Then for output, connect a HD15 VGA->BNC breakout


I bought and like this one (3814231738)
http://krysgates.tripod.com/2639701.jpg


but I also bought these to try (5701097576)
http://pws.prserv.net/usinet.rdrumm/7vgacables1.JPG


then run 16' of quality Canare/Belden cables with BNC to your PG9X.


One remote, one cable run.


-Clarence

Sorry, I'm visiting family out of state and haven't had much access to the net. Just now getting my AVS fix.


No, Clarence, I'm not doing an HTPC. We have 5 PC's in this house but none of them will be in the HT, and I don't want to have to spend the $$$ to build a new one. The Momo is attractive because it produces a very good picture without needing an HTPC, and it's a lot cheaper/easier than the HTPC. So all the capture card &etc solutions won't work for me.


Good to know the TVone works so well. I'll plan to go with that for non-DVD sources. What are those short breakout cables, Clarence? Geeze, you have even more of those than you have projectors.


So if I can use the TVone for a simple scaler & switcher, there's really no need to run an S-video cable to the PJ for legacy sources. Everything will be scaled and converted to RGBHV through the VGA output. Clarence, did you get a chance to compare Momo -> PJ to Momo -> TVone -> PJ to make sure the TVone passthrough didn't degrade the signal?


Gary

Quote:
Actually, that's not quite right. Y'Cb'Cr is a packed pixel format, used for digital color coding like in MPEG and other codecs, while Y'Pb'Pr is used for analog color coding. So in your standard set of component video cables, one cable carries Y (luminance of the dot), one cable carries Pb (blue chrominance) and the other Pr (red chrominance). There are several different types of Y'Cb'Cr in use but as far as I know only one type of Y'Pb'Pr (the "consumer equipment" type). These color coding types together are loosely referred to as YUV. So DVD and HD both are Y'Cb'Cr coded for MPEG. Once they've completed the MPEG decoding stage (in a set-top box, for example) is when they may or may not be converted to Y'Pb'Pr, depending on the output in use.


Did that make any sense at all?


-Bob