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Advanced Topics

Quadro SDI Output PG-03776-001_v06 | 57

In the 8-bit case, Y ranges from 16 – 235 while CrCb ranges from 16 – 240. The default

scale values for Video Range are then similar:

scale

y = (235 – 16) / 256 = 0.85547

scale

cr = (240 – 16) / 256 = 0.875

scale

cb = (240 – 16) / 256 = 0.875

To perform color space conversion into what is frequently referred to as Film Range or

Full Range a custom color space conversion must be specified via the API. In the case of

10-bit full range, Y and CrCb ranges [4,1019]. The scale values are then computed as

follows:

scale

y = (1019 – 4) / 1024 = 0.992

scale

cr = (1019 – 4) / 1024 = 0.992

scale

cb = (1019 – 4) / 1024 = 0.992

10.3.3 Offset

The value of offsety is calculated as the ratio of the minimum value of luma within the

range to the maximum value of luma within the range. In the case of 10-bit Video

Range, offset

y calculated as follows:

offset

y = (64 / 1024) = 0.0625

Meanwhile, the values of offset

cr and offsetcb are calculated as the middle point of the

range divided by the maximum value in the range. Therefore, in the case of the 10-bit

Video Range, the following calculation is used:

offset

cr = offsetcb = ((64 + 960) / 2) / 1024 = 0.5

Another way to think about offset

cr and offsetcb is as the value required to move the

minimum result from the matrix multiplication and scale into the range of [0-1].

In the case of Full Range the 10-bit offset values are then computed as follows:

offset

y = (4 / 1019) = 0.003925417

offset

cr = offsetcb = ((4 + 1019) / 2) / 1024 = 0.5

An application can override this default color space conversion behavior as outlined in

Code Listing 43 for Windows and Code Listing 44 for Linux. However, applications

should be aware that the final SDI output color range is always clamped to the following

legal values.

8-bit Range: 4 – 251

10-bit Range: 4 – 1019

12-bit Range: 16 - 4079





Note: Refer to Chapter 11 for a summary of the matrix coefficients as well as scale

and offset values for typical full and video range color space conversions.

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