PDA

View Full Version : Black Level Setup, 0 or 7.5?



magendim
10-10-2003, 06:04 PM
This probably has been discused before, but what's the correct black level in the Toaster settings, 7.5 or 0? We're capturing mainly YUV from a Sony BetaSP UVW-1600 deck, occasionley from Hi-8/SVHS.

Thanks,
Mike

Jim Capillo
10-10-2003, 06:34 PM
7.5

bradl
10-10-2003, 10:16 PM
YUV color space defines black as 0 IRE (Sony has not always complied to this however). Also, NTSC 601 Digital Video uses 0 IRE blacks. Additionally, the entire world, except for US, uses black at 0 IRE.

NTSC Composite output uses 7.5 IRE black.

I am not saying exactly where you should set your blacks just passing on some observations...

bradl
10-10-2003, 11:41 PM
I just ran across this very informative 5 minute tutorial on "What is Black Level Setup" (http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf)

It is a Flash presentation that discusses Black Level in Analog, Digital, DV, etc.

vanguard
10-13-2003, 07:43 AM
The 7.5 forced setup issued developed because Sony chose to have the Betacam (and BetaSP) Component signals run at the Japanese 0IRE for Black. The composite runs at 7.5IRE.

Every other deck made for the US market has 7.5IRE as the black level.

So if you are using a Sony beta deck in component you want 0IRE, in composite you want 7.5IRE.

If like us, you have a BetaSP and an MII deck hooked up at the same time, hook the Beta deck up composite to keep fom having to switch back and forth, and leave it at 7.5IRE.

The reason for 7.5IRE was prior to the NTSC (Never Twice the Same Color) comittee rulings on color transmission the FCC determined that when B&W signals have no "Setup" (Called this because the "Black" is set 7.5IRE up from 0IRE), the early transmitters/recievers were extremely succeptable to interference due to the (nearly) un-modulated signal. The 7.5IRE gave them a wee signal to keep the snow down, and didn't adversly affect the "Black" portion of the recieved signal. Especially on a 1940 Sylvania Halo-Light TV with all that contrast.... (sarcasm there)

Anyways thare you go.

7.5 is fine for all things NTSC here in the US, except Beta component.

GregGerlach
10-13-2003, 12:22 PM
The only question I've had deals with how the 7.5 ire setup interacts with the TMPGenc plugin. It would seem to me that the 7.5 ire option has no effect when you use the plugin to make an Mpg2 file. I noticed that when I made an Mpg2 file with TMPGenc, the black levels were noticeably lower. I e-mailed Kirk Morger who developed the plugin and he says that to remedy this, I should select the "Output YUV data as basic YCbCr not CCIR601" within TMPGenc. Just wondering if anyone else has dealt with this issue.

Greg Gerlach
Lexington, KY

Jim_C
10-13-2003, 12:57 PM
>>I should select the "Output YUV data as basic YCbCr not CCIR601" within TMPGenc. Just wondering if anyone else has dealt with this issue.

That is correct.

This:
Output basic YCbCr
Enabled (see below)

Generally, you should select this option; it will preserve the original contrast of your source footage. If your source footage is high-contrast computer-generated animation, disabling this option will ensure its brightness and saturation remain within "legal" video limits. Some DV codecs seem to automatically compensate for this difference between video signal and digital colour range, which will make the resulting output seem too dark. If you notice the MPEG file looks darker than the DV original (the difference will be something around 8%), try disabling this option and see if that corrects the problem. Sony's and Canopus' codecs seem to keep the original range when decoding (meaning this option should be enabled). I have been told that Adaptec's and MainConcept's DV codecs perform automatic range scaling when decompressing, so if you're using one of these, disable this option. If you have information regarding other DV codecs, send me an e-mail (use the menu on the left).

was taken from here:
http://dvd-hq.info/Compression.html

magendim
10-13-2003, 03:38 PM
Thanks for the posts. Clears things up. We only use the Beta composite signal for monitoring and capture using component, so just have to remember to switch it back to 7.5 if we capture SVHS or Hi-8.

I assume DV or analog component out of a JVC DV/VHS deck will be 0 IRE, correct? There have been some instances where we captured DV using the analog component output so that the field order was consistent with the Hi-8 captures.

I had seen the JVC tutorial before I posted the origional question, it's actually very informative.


Mike