5D Moire and Aliasing and Cineform at DVinfo.net

Chris Barcellos · June 22nd, 2009, 03:25 PM

Am I imagining things or is it possible the conversion to CFHD reduces moire and aliasing showing up in the original footage? Anybody have an explanation of why, if that is so ?

Charles W. Hull · June 22nd, 2009, 04:30 PM

Quote:

Originally Posted by Chris Barcellos

Am I imagining things or is it possible the conversion to CFHD reduces moire and aliasing showing up in the original footage? Anybody have an explanation of why, if that is so ?

I had not noticed any difference - but I wasn't looking. I have some clips where aliasing is a real problem so I'll take a look this evening.

David Newman · June 22nd, 2009, 07:34 PM

Based on the title I thought this was going to me a bad thread. :) The 5D moire/aliasing is due the wrong opictal low pass filter in the camera, and/or no vertical software filter (not summing multiple lines.) I'm sure you guys know that, so that was for the casual reader. Generally nothing much can be done for moire, but aliasing can be slightly reduced with wavelet compression vs DCT (we are talking very slight.) Maybe you are seeing that.

Chris Barcellos · June 22nd, 2009, 09:31 PM

Sorry David, did not mean to scare you.... i'll see if I can come up with an example.

Chris Barcellos · June 22nd, 2009, 09:45 PM

Here are two grabs, one from cineform, and one right from original clip. Check out shirt under chin of man in foreground.

I am not converting at highest level from NeoScene, perhaps that is keep the moire down ?

(now edited with proper grabs)

Charles W. Hull · June 22nd, 2009, 09:57 PM

Quote:

Originally Posted by Charles W. Hull

I had not noticed any difference - but I wasn't looking. I have some clips where aliasing is a real problem so I'll take a look this evening.

Chris, my sample clip looks the same, MOV and AVI. This is a clip of some power line construction, a crew working with a helicopter. The power lines have heavy aliasing.

I brought both the MOV and AVI into CS4 and exported them to MP4 so I could see them in the same viewer with the same codec (CoreAVC). I can't tell them apart.

Chuck

David Newman · June 22nd, 2009, 10:03 PM

I think the default decoders Quickime is using has edge enhancement (bad.) Look at the dark outlines around the white text on the bottle label. You can add edge enhancement, but you can't remove it, so we don't do that. I think that is what you are seeing.

June 22nd, 2009, 03:25 PM	#1
Chris Barcellos Inner Circle Join Date: Nov 2005 Location: Elk Grove CA Posts: 6,838	5D Moire and Aliasing and Cineform Am I imagining things or is it possible the conversion to CFHD reduces moire and aliasing showing up in the original footage? Anybody have an explanation of why, if that is so ? __________________ Chris J. Barcellos

June 22nd, 2009, 07:34 PM	#3
David Newman CTO, CineForm Inc. Join Date: Jul 2003 Location: Cardiff-by-the-Sea, California Posts: 8,095	Based on the title I thought this was going to me a bad thread. :) The 5D moire/aliasing is due the wrong opictal low pass filter in the camera, and/or no vertical software filter (not summing multiple lines.) I'm sure you guys know that, so that was for the casual reader. Generally nothing much can be done for moire, but aliasing can be slightly reduced with wavelet compression vs DCT (we are talking very slight.) Maybe you are seeing that. __________________ David Newman -- web: www.gopro.com blog: cineform.blogspot.com -- twitter: twitter.com/David_Newman

June 22nd, 2009, 09:31 PM	#4
Chris Barcellos Inner Circle Join Date: Nov 2005 Location: Elk Grove CA Posts: 6,838	Sorry David, did not mean to scare you.... i'll see if I can come up with an example. __________________ Chris J. Barcellos Last edited by Chris Barcellos; June 22nd, 2009 at 10:02 PM.

June 22nd, 2009, 09:45 PM	#5
Chris Barcellos Inner Circle Join Date: Nov 2005 Location: Elk Grove CA Posts: 6,838	Example Here are two grabs, one from cineform, and one right from original clip. Check out shirt under chin of man in foreground. I am not converting at highest level from NeoScene, perhaps that is keep the moire down ? (now edited with proper grabs) Attached Thumbnails __________________ Chris J. Barcellos

June 22nd, 2009, 10:03 PM	#7
David Newman CTO, CineForm Inc. Join Date: Jul 2003 Location: Cardiff-by-the-Sea, California Posts: 8,095	I think the default decoders Quickime is using has edge enhancement (bad.) Look at the dark outlines around the white text on the bottle label. You can add edge enhancement, but you can't remove it, so we don't do that. I think that is what you are seeing. __________________ David Newman -- web: www.gopro.com blog: cineform.blogspot.com -- twitter: twitter.com/David_Newman