Capturing, Noise and Jagged Reds at DVinfo.net

Christian Bertolini · September 3rd, 2006, 03:26 AM

Hi guys,

please a quick question, I've been capturing from my XL H1 to Final Cut with the standard HD FCP preset via Firewire, I'm using a Dell 24", and I noticed the following issues:

- Reds are jagged.
- I see a bit of noise in the dark areas whit the footage at full screen (Coring at 0 and NR1 and NR2 are off).
- the footage captured at 50i shows jagged contours all the time; at 24F it doesn't.

1) Can these issues be solved by using the HD SDI pulldown? In this case what are the FCP pulldown settings?

2) Can I use different settings or software for Firewire capturing on Mac?

3) any advice?

Thanks a lot for your help
Have a good monday

Christian

Brian Critchlow · September 3rd, 2006, 03:50 PM

Christian, addressing the jagged playback of 50i, I am almost positive that you are running into the issue of watching an interlaced signal on a progressive LCD monitor. If you want to see proper playback, export it to an interlaced TV.
If your final product is to be shown in a progressive manner (Film, progressive DVD) then pulldown (reverse pulldown, however you want to phrase it) can fix this. After effects has been most useful for me because it does an automatic pulldown detection which saves time.

Regarding the noise, depending on how sensitive you are to noise, it is most likely the inherent noise in the signal that just cant be eliminated, or you are running with gain on.

The red jagged stuff I have no clue whats up with that.

John McManimie · September 3rd, 2006, 05:02 PM

The "jagged reds" problem is probably the chroma sawtoothing effect that can occur with 4:2:0 interlaced images. It is mentioned in the Texas Shootout (http://dv.com/features/features_item...leId=192501232) and was seen with the Sony HVR-Z1U and the Canon XL-H1. Chroma blur can help.

Derek Prestegard · September 17th, 2006, 06:06 PM

Definately due to chroma subsampling. There is MUCH less chroma information than luma information. To fill the screen with chroma, the chroma plane has to be interpolated. Frequently this is done with a crappy linear or point resize algorithm. You know, like scaling a sprite back in the old dos days. Big. Ugly. blocks. Bright red seems to be most vulnerable to this. It's a problem with all MPEG codecs b/c they use aggressive chroma subsampling...

:)

If only the subsampling algorithms used good resizers like bicubic or lanczos... In fact, lots of electronics could be improved with better scalers. Especially LCD screens omg..

You are probably also seeing interlacing artifacts. Interlacing is just plain stupid. It's a pitiful analog compression method that was relevant in the 1950s. Too bad everything is STILL hardwired for it.

Interlacing actually makes digital compression HARDER :)

Sorry for rambling :)

~Derek

September 3rd, 2006, 03:26 AM	#1
Christian Bertolini New Boot Join Date: Aug 2006 Location: Australia Posts: 16	Capturing, Noise and Jagged Reds Hi guys, please a quick question, I've been capturing from my XL H1 to Final Cut with the standard HD FCP preset via Firewire, I'm using a Dell 24", and I noticed the following issues: - Reds are jagged. - I see a bit of noise in the dark areas whit the footage at full screen (Coring at 0 and NR1 and NR2 are off). - the footage captured at 50i shows jagged contours all the time; at 24F it doesn't. 1) Can these issues be solved by using the HD SDI pulldown? In this case what are the FCP pulldown settings? 2) Can I use different settings or software for Firewire capturing on Mac? 3) any advice? Thanks a lot for your help Have a good monday Christian

September 3rd, 2006, 03:50 PM	#2
Brian Critchlow Regular Crew Join Date: Dec 2005 Location: Santa Cruz, CA Posts: 133	Christian, addressing the jagged playback of 50i, I am almost positive that you are running into the issue of watching an interlaced signal on a progressive LCD monitor. If you want to see proper playback, export it to an interlaced TV. If your final product is to be shown in a progressive manner (Film, progressive DVD) then pulldown (reverse pulldown, however you want to phrase it) can fix this. After effects has been most useful for me because it does an automatic pulldown detection which saves time. Regarding the noise, depending on how sensitive you are to noise, it is most likely the inherent noise in the signal that just cant be eliminated, or you are running with gain on. The red jagged stuff I have no clue whats up with that.

September 3rd, 2006, 05:02 PM	#3
John McManimie Major Player Join Date: Mar 2004 Location: Portland, OR Posts: 314	The "jagged reds" problem is probably the chroma sawtoothing effect that can occur with 4:2:0 interlaced images. It is mentioned in the Texas Shootout (http://dv.com/features/features_item...leId=192501232) and was seen with the Sony HVR-Z1U and the Canon XL-H1. Chroma blur can help.

September 17th, 2006, 06:06 PM	#4
Derek Prestegard Regular Crew Join Date: Sep 2006 Location: Santa Cruz, California Posts: 30	Definately due to chroma subsampling. There is MUCH less chroma information than luma information. To fill the screen with chroma, the chroma plane has to be interpolated. Frequently this is done with a crappy linear or point resize algorithm. You know, like scaling a sprite back in the old dos days. Big. Ugly. blocks. Bright red seems to be most vulnerable to this. It's a problem with all MPEG codecs b/c they use aggressive chroma subsampling... :) If only the subsampling algorithms used good resizers like bicubic or lanczos... In fact, lots of electronics could be improved with better scalers. Especially LCD screens omg.. You are probably also seeing interlacing artifacts. Interlacing is just plain stupid. It's a pitiful analog compression method that was relevant in the 1950s. Too bad everything is STILL hardwired for it. Interlacing actually makes digital compression HARDER :) Sorry for rambling :) ~Derek