IRE and Input Levels - Requesting very basic help.

[JimmyD123456]

Hello, and thank you for this wonderful site and forum.

I recently received a Samsung DVD-R120 stand alone DVD recorder as a gift and I'm having a bit of trouble figuring out the correct video settings.

I've read the four page thread on IRE settings but, to be honest, I couldn't make heads or tails of it. I think it's a little TOO detailed and complicated for newbies like myself.

In the video setup section of my DVD recorder it has three video settings I'm confused about.

"Input Level" -> options are "Darker" or "Lighter"

"Black Level" -> options are "0 IRE" or "7.5 IRE"

"3D Noise Reduction" -> options are "Off" or "On"

I should point out that none of these settings are thoroughly addressed in the product's instruction manual.

My questions are as follows:

1. Will these settings have an impact on the actual recordings, or are they just output settings that will affect "what I see" while watching something on the player end? My goal is to make the highest (or at least correct) quality recordings. If these are just output settings, then it won't affect the recordings and I suppose I can set them to whatever settings "look the best." Will these settings have an impact on what gets recorded?

2. If these settings matter to the recording, and not just "what I see," can someone please, simply, without a big production, just tell me what these settings should be at. If you know a lot more about this stuff than I do (and you must) what would you set these options to on YOUR recorder?

Thank you so much for any help you can provide.

P.S. Not that it matters, but to my naked eye it looks like the "best" setting is Input Level -> Darker, Black Level -> 7.5 IRE, and 3D Noise -> not sure. Thanks again!

[edDV]

They should be clear whether you are adjusting input or output.

For North America 7.5 IRE should be used for everything other than a DV camcorder connected analog to the input. Output should be 7.5 IRE if you are given a choice.

"Darker vs lighter" - not clear what they are adjusting so use trial and error.

"3D Noise Reduction" - This will have some image quality tradeoff so turn it off for clean sources.

[JimmyD123456]

edDV,

Thank you very, very much. That's exactly the info I was looking for, and you made it very easy to understand. Thanks a million!

[anitract]

edDV, I've read most of what you're written on IRE levels on here. Good stuff.

Anyway, for the record, are you saying that you recommend NOT adjusting 7.5 IRE sources (such as VHS) down to 0 IRE? If this is so, I'm curious why. Many people like gshelly61 recommend just the opposite.

[Cornucopia]

don't know why they say that. You're in the US. Use 7.5.

Scott

[wulf109]

My only expierence with IRE levels is with DVD players running OFFA 1.5 firmware which allow you to turn IRE no or off. Clearly to my eye the picture with IRE off is darker with much better contrast. With IRE on at 7.5 the picture is noticeably washed-out,blacks look grey.

[edDV]

edDV, I've read most of what you're written on IRE levels on here. Good stuff.

Anyway, for the record, are you saying that you recommend NOT adjusting 7.5 IRE sources (such as VHS) down to 0 IRE? If this is so, I'm curious why. Many people like gshelly61 recommend just the opposite.

Well, it all depends what that switch does. Industry practice usually names the switch for the input characteristic. "7.5 IRE" usually means the video coming in has black at 7.5 IRE. This is true for America's NTSC.

The DVD recorder will take that 7.5IRE analog black and map it to digital level 16 which is black level for DVD.

Most consumer DV camcorders output ANALOG black at "Japan NTSC 0.0 IRE" level. With the DVD recorder switch at "0.0IRE", 0.0IRE gets mapped to digital level 16.

If you transfer DV camcorder video over IEEE-1394, black is already at digital level 16 so no problem. The exception is Pass-Through captures where the input had 7.5 IRE black. In that case analog 7.5 IRE gets mapped to digital level 32. That should be adjusted back down to level 16 to prevent a "washed out" look.

Ref: http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf

[edDV]

My only expierence with IRE levels is with DVD players running OFFA 1.5 firmware which allow you to turn IRE no or off. Clearly to my eye the picture with IRE off is darker with much better contrast. With IRE on at 7.5 the picture is noticeably washed-out,blacks look grey.

Some early DVD recorders had levels problems. They had incorrect black level calibration causing the level 32 "washed out" problem. Current generation recorders have mostly fixed this.

[anitract]

I seem like I should know this, but...digital level 16 is what again? Is this where black is at IRE 0?

[edDV]

I seem like I should know this, but...digital level 16 is what again? Is this where black is at IRE 0?

"IRE" is strictly defined as an analog value that references blanking for zero. In digital video, level 16 corresponds to black or zero % video. White (100%) video is at digital level 235. The range 236-255 is reserved for white overshoots. Clipping occurs at level 255 or 108%

[anitract]

Thanks for the clarification. So then does that make level 32 the American NTSC (with black at 7.5 ire)? Trying to absorb just a _little_ jargon.

[Cornucopia]

No, the range of 601-acceptable luminance values is 16-235, 16 = darkest Black (Digitally)

So 16D = 0 IRE Analog (in PAL, and in Japanese NTSC)
and 16D = 7.5 IRE Analog (in US NTSC)

32D would be ~10 IRE (PAL, J_NTSC) and ~15.5 IRE (US_NTSC)

Scott

[edDV]

Exactly,

Here is an example from the golden oldies of the difference of level 32 and level 16 black. The difference would appear greater on a TV since TV gamma puts more weight to dark level differences.

[hrlslcbr]

Watch this. It helps a lot

http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/jvc_demo.swf
It's a flash animation explaining the basics of IRE and how that is mapped to digital levels.

EDIT: Oh, it seems edDV already posted about this...

[anitract]

Ah, thank you, guys. Makes sense. You should've seen the little light bulb literally appear above my head.