[QuadList] IVC Recovery--"Capture" and "Banding"--

Sat May 17 23:40:17 CDT 2014

OK!  Great info  Ted.
Most of  what I deal with is  B/W

but the banding  I see   in the edits we do on color  news stuff if it is 8 
bit in  Sony Vegas.. and  goes away   when I go  32  but.

In a message dated 5/17/2014 9:34:00 P.M. US Mountain Standard Time,  
ted at quadvideotapegroup.com writes:

On May 17, 2014, at 7:17 PM, _couryhouse at aol.com_ 
(mailto:couryhouse at aol.com)  wrote:

I just  bring it into digital and  hit  the  save a  still in Sony   
Vegas...   or if  I am watching analog    footage in  windows media  player  I  do 
a screen  capture..... 

I think what Park meant by "capture an image" was "digitize  video" not 
make a still.  

His particular process converts composite video to component using the  
Accom D-Bridge 10-bit decoder before capture as a file... say as 10-bit YUV  
4:2:2 in a Quicktime wrapper.

The D-Bridge products (122 and 221) have roots in companies formed by  
former Ampex engineers:

http://www.abekas.com/main/history//page1059.htm

They were intended to "Bridge" the analog to digital process, including  
analog composite, D1 parallel and D2 composite.

In a message dated 5/17/2014 4:52:15 P.M. Mountain Standard Time, 
_park at videopark.com_ (mailto:park at videopark.com)  writes:

This is a low band color image from the late 60s,  taken with a TK-42.  
Notice the lack of banding, hanging dots and  cross-color contamination.

The word "banding" can mean two things as related to this post:  

Quad banding... where one sees variations every 16 lines (NTSC) caused  by 
differences in reproduction by each head (EQ, luma, chroma levels for  
example.)

Or noticeable bands in light to dark areas of the picture caused by the  
number of bits used in the digitization process. 

You might see this on say a cyc wall where the top is darker than the  
bottom. Skies are also an example of where banding might easily occur.  

An 8-bit digitization step (255 steps per color) might be more likely  to 
cause a noticeable bands of luma or chroma. 10-bit digitization provides  
1023 steps per color, so banding is less likely to occur.

Here's Larry Jordan's take on it with a visual example (originally  written 
in 2007 when ProRes was released):
http://www.larryjordan.biz/why-video-bit-depth-matters/

More bits and a better representation of the  original analog signal is one 
reason why the generally preferred Archival file  for SD is 10-bit YUV 
4:2:2, and in a Quicktime wrapper, although some  archives use AVI if they're PC 
based.

Ted

Ted  Langdell
Secretary
Skype:   TedLangdell
e-mail: _ted at quadvideotapegroup.com_ (mailto:ted at quadvideotapegroup.com) 

Seventh  Annual Quad Videotape Group Dinner at AMIA:  7pm, Tuesday, October 
7.  2014, Savannah, Georgia
Eighth  Annual Quad Videotape Group Lunch at NAB:  12:30pm on Tuesday, 
April 14,  2015, Las Vegas Convention  Center

=

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Please  trim posts to relevant info when replying.

Change subject to reflect  thread direction.  Thanks.
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