3.0 Digital Processing and Functionality
3.2 Effects
Bt860/861
Multiport YCrCb to NTSC/PAL /SECAM
3.2.7 Programmable Video Adjustments Controls
Registers Y_OFF, M_Y, M_CB, M_CR, and PHASE_OFF program video
adjustment controls for hue, brightness, contrast, saturation, and sharpness.
3.2.7.1 Hue Adjust
There are two methods for adjusting the hue. Only one method should be enabled
at any time. While using one method, the registers of the other should be set to
their default values.
Method 1—adjusts the subcarrier phase within the active video region.
Register HUE_ADJUST (3B[7:0]) controls the subcarrier phase. This method
adjusts the hue in composite and S-Video signals for PAL and NTSC waveforms
according to the following equation:
HUE_ADJUST = 256 ×(phase offset) ⁄ 360°
Method 2—uses the four registers MULT_UU, MULT_VU, MULT_UV, and
MULT_VV to matrix multiply the color vectors.
These registers are used to perform a 2x2 matrix multiplication on the U/V
path (or D /D path for SECAM). Matrix multiplication transforms the incoming
R
B
U/V stream into an outgoing U/V stream preceeding the color modulator. The
default values leave the U/V stream unmodified. The parameters are 8-bit twos
complement numbers.
The formulas implemented by these registers are as follows:
Uout = (MULT_UU/128) × Uin + (MULT_VU/128) × Vin
Vout = (MULT_UV/128) × Uin + (MULT_VV/128) × Vin
The value 0x7F is a special case which is rounded up internally to +128, or a
factor of 1.00 after the multiplier is divided by 128.
These registers can be loaded with sine and cosine values as follows to
perform a hue rotation on the chrominance values, except a value of +127 is made
128 internally.
To rotate the hue by an angle θ, program the matrix multipliers as follows:
MULT_UU = 128 × cos (θ)
MULT_VU = –128 × sin (θ)
MULT_UV = 128 × sin (θ)
MULT_VV = 128 × cos (θ)
Method 2 (matrix multiplication) cannot be used for hue rotation when the
PAL bit is enabled. However, hue rotation can be accomplished for PAL modes in
one of two ways. For component modes, method 2 hue rotation (matrix
multiplication) is effective if register bit PAL (16[3]) is set to 0. For composite
and S-Video modes, in which register bit PAL is enabled, method 1 hue rotation
(subcarrier phase adjust) is effective. Hue rotation cannot be implemented
simultaneously for component and composite PAL modes.
When in SECAM mode, this matrix multiplication occurs in D /D space,
R
B
and, as a result, the angle should be the negative of what one would expect if the
data was in the U/V space for PAL or NTSC.
3.2.7.2 Brightness
Adjust
Brightness adjust is controlled by register Y_OFF (37[7:0]). Y_OFF is a twos
compliment number, such that a value of 0x00 is 0 IRE offset, a value of 0x7F is
+22.14 IRE offset, and a value of 0x80 is –22.31 IRE offset. The luminance level
offset is referenced from black and can be adjusted from –22.31 IRE (below
black) to +22.14 IRE (above black). Active video is added to the offset level.
3-20
Conexant
D860DSA
CONEXANT [ CONEXANT SYSTEMS, INC ]
