Is RGB or YUV the best input to a scaler

T

tommo2

Guest
OK
I have my barco data 701s up and running. The iScan HD is on the way. Im just about to order cables.
Heres what i want to do:

The iScan output will be VGA TO RGBS BNC TO PROJECTOR.
The dvd output to the iScan can be either RGB or YUV
The satellite box output can be either RGB or YUV
Which is best to feed the iScan???? RGB or YUV.

Ive heard that the best output to PJ is RGB and that is what im going for. Wouldn't that mean that the best input to feed the iScan is RGB also????

Thanks Y'all
 

Chris Frost

Well-known Member
tommo2 said:
Ive heard that the best output to PJ is RGB
Generally true because it's the same way the pj reproduces the picture and that means less processing by the pj. (3 x CRTs R-G-B, 3 x LCDs R-G-B or 3 x DLP colour wheel phases R-G-B, you get the drift yeah)

tommo2 said:
Wouldn't that mean that the best input to feed the iScan is RGB also????
Only if the source is inherently RGB.

A Skybox is RGB. A DVD player is Component. Use RGB from Sky and YPbPr from a DVD for best signal performance.

Rule of thumb is 'Fewer processing stages the better'
 
T

tommo2

Guest
RGBS: RGB with composite sync on 4th connection (I think)

The PJ has 4 BNC connectors for RGB input labelled R-G-B-S
It can be connected with seperate composite sync, tri-level sync, or bi-level or with sync on green(RGsB).
This raises another q:
What is the best config???
I thought seperate composite sync would be better but this is not based on anything other than my own unexperienced assumptions.
God this is getting complicated.....;)


BTW: What are porch settings???
 

Welwynnick

Distinguished Member
Oh dear, am I going to tread on Chris's toes again?

Displays are generally RGB, so that's best for the scaler output. My understanding is that RGBHV is better than RGBS is better than RGsB, but the differences really aren't that great, and RGBS will probably be fine ( as in can't tell the difference). I think as long as the sync pulses are off the signal lines, that's great, and they run at higher, more robust voltage. 5V vs 0.3V I think.

Sources are generally component, though, so that will probably be best. Digital video is stored and broadcast as YCbCr 4:2:0 MPEG 2 (or 4 or VC-1 etc) in order to compress it effectively without compromising quality. The player / receiver will decode, decompress and transcode this to RGB, but those processes are best performed in the scaler where possible. Remember the scaler may be performing it's video processing functions in component, rather than RGB space (because it's more economical of processing power).

The answer is of course to suck it and see, but I wopuld always go for component in and RGBHV out.

BR, Nick
 
T

tommo2

Guest
i only have 1 sync input. does this mean that i have to have comp sync????
 

Chris Frost

Well-known Member
welwynnick said:
Oh dear, am I going to tread on Chris's toes again?
No, I don't think you are. :nono:

welwynnick said:
Displays are generally RGB, so that's best for the scaler output. (Yes, that's what I said, so what's the problem?) My understanding is that RGBHV is better than RGBS is better than RGsB, but the differences really aren't that great, and RGBS will probably be fine ( as in can't tell the difference). I think as long as the sync pulses are off the signal lines, that's great, and they run at higher, more robust voltage. 5V vs 0.3V I think.

Sources are generally component, (Well how exactly you propose to get Component out of a regular Sky box then?) though, so that will probably be best. Digital video is stored and broadcast as YCbCr 4:2:0 MPEG 2 (or 4 or VC-1 etc) in order to compress it effectively without compromising quality. The player / receiver will decode, decompress and transcode this to RGB, but those processes are best performed in the scaler where possible. Remember the scaler may be performing it's video processing functions in component, rather than RGB space (because it's more economical of processing power). (So, long answer short is DVD players are Component and Sky boxes are RGB, and the fewer processes the better, right? Well isn't that exactly what I said :rolleyes: )

The answer is of course to suck it and see, but I wopuld always go for component in and RGBHV out.

BR, Nick
 

Welwynnick

Distinguished Member
Chris Frost said:
Only if the source is inherently RGB.
I can't think of any digital video sources that are inherently RGB. To the best of my knowledge, all storage and broadcast video formats are essentially component, and any RGB output will have gone through an unnecessary transcoding stage. It's true that the regular Sky box is RGB or worse, but the original poster did say that his satellite box could output YUV, so that would probably be slightly better.

I do strongly agree though, that in all areas of video and audio reproduction, the fewer processes the better.

regards, Nick
 
T

tommo2

Guest
okay, now im a bit confused. :confused:
You both say that ur agreeing with one another but i dont think so.:nono:
RGB from scaler to pj is fine.:smashin:
YUV from dvd to scaler is fine.:smashin:
What do i do from sky box... RGB or YUV:lease:
I'm on the brink of ordering a scart to component cable for sky box... is this okay? Also, can the scart-component cable also be used for RGB, or are the pins within the scart different for RGB and component.
I need to know this before i order the cable.:suicide:

The cable i have in mind is this one:

http://cgi.ebay.ie/ws/eBayISAPI.dll?ViewItem&item=5799815111&rd=1&sspagename=STRK:MEWA:IT&rd=1

Any thoughts let me know.

Thanks y'all:thumbsup:

EDIT: Just been to wikipedia... it seems that the same scart cable can output either RGB or Component (on the same scart pins) depending on the sky box setting... Is this true.????
If so then i can order the cable and experiment with either RGB or component from sky box and see which is best....
Here's hoping....
 

Welwynnick

Distinguished Member
No, you can't get YUV from a Sky box, you have to use RGBS from scart, so even a scart-component cable won't do (you will miss the sync line). The cable you found will only work with a source that can output component from scart, and Sky won't, unfortunately. You would need a scart to RGBS lead, which your iScan should accept (better check first, because not all scalers do).

Nick
 
T

tommo2

Guest
Is there any such thing as a scart to RGBS cable... i cant find one anywhere. It would have to be 15m long aswell.
 

Mad Mr H

Well-known Member
tommo2 said:
Is there any such thing as a scart to RGBS cable... i cant find one anywhere. It would have to be 15m long aswell.

RGBS from a scart lead.

the "S" is the composite video output, it uses pins 17 and 19 and takes the sync from there, just in case anyone wants to make their own cable.
 

hornydragon

Distinguished Member
why 15m? thats "long" and sky boxes dont have the most stable output, can you not move the sky box closer to the scaler?
 
T

tommo2

Guest
The sky box is downstairs. The pj is upstairs. The pj will be mainly used for dvds but i would like to watch the occasional match via sky on pj.
This means the cable will have to be around 15m long
 

The latest video from AVForums

Star Wars Andor, Woman King, more Star Trek 4K, Rings of Power & the latest TV, movies & 4K releases
Subscribe to our YouTube channel

Full fat HDMI teeshirts

Support AVForums with Patreon

Top Bottom