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

[Charles Park Seward]

Thanks, Ted. Nice summation.

Junaid told me the noise reducer was their first Accom product and he wrote the software.

Accom’s first product to be introduced was the “DIE-422” — a Digital Image Enhancer. This machine was used in the film-to-tape transfer process, electronically removing film dirt and scratches, as well as providing overall image enhancement capabilities.

Just to help understanding, I think I would use the word "contouring" and not banding to describe the bands in a image with 8-bit video, especially when talking about Quad video. . Our video stays 10-bit all the way from the analog input to the digital MOV file. 

Quantel developed "Dynamic Rounding" to make 8 bits look as good as 10.

Dynamic Rounding - Dynamic Rounding is a technique devised by Quantel for truncating the word length of pixels – a process you can't avoid when you are processing images. Rather than simply losing the lower bits, Dynamic Rounding uses their information to control, via a randomiser, the dither of the LSB of the truncated result. This effectively removes any artefacts that would otherwise be visible. Dynamic rounding is non-cumulative on any number of passes and produces statistically correct results. Dynamic rounding eliminates any truncation artefacts.

It is also used on images that were created on their boxes, like in a Paintbox image. 

We have some Quantel equipment (Editbox, Paintbox, Hal) and Dynamic Rounding really works.

One feature of the D-Bridge is to take in digital D-2 and convert it to digital D-1 (digital composite to digital component), keeping it digital all the way.

Best,
Park

C. Park Seward
Cell: 818-535-2747
Home: 541-476-6657
2" Quad and 1" "C" transfers and more
The Transfer Lab at Video Park
Visit us: http://www.videopark.com





On May 17, 2014, at 9:33 PM, Ted Langdell <ted at quadvideotapegroup.com> wrote:

> 
> On May 17, 2014, at 7:17 PM, 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 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
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