bt829bkrf ETC-unknow, bt829bkrf Datasheet - Page 35

• Manufacturer Part Number: bt829bkrf
• Description: Video Streamii Decoders
• Manufacturer: ETC-unknow

Bt829B/827B
VideoStream II Decoders
1.7.4 Chrominance Scaling
1.7.5 Scaling Registers
A 2-tap, 32-phase interpolation filter is used for horizontal scaling of chromi-
nance. Vertical scaling of chrominance is implemented through chrominance
comb filtering using a line store, followed by simple decimation or line dropping.
Horizontal Scaling Ratio Register (HSCALE)
horizontal scaling ratio. When outputting unscaled video (in NTSC), the Bt829B
will produce 910 pixels per line. This corresponds to the pixel rate at f
(4*Fsc). This register is the control for scaling the video to the desired size. For
example, square pixel NTSC requires 780 samples-per-line, while CCIR601
requires 858 samples-per-line. HSCALE_HI and HSCALE_LO are two 8-bit reg-
isters that, when concatenated, form the 16-bit HSCALE register.
ing formula should be used to determine the scaling ratio to be entered into the
16-bit register:
where:
For example, to scale PAL/SECAM input to square pixel QCIF, the total number
of horizontal pixels is 236:
An alternative method for determining the HSCALE value uses the ratio of the
scaled active region to the unscaled active region as shown below:
where:
The method below uses pixel ratios to determine the scaling ratio. The follow-
NTSC:
PAL/SECAM: HSCALE = [ ( 1135/P
HSCALE = [ ( 1135/236 ) – 1 ] * 4096
NTSC:
PAL/SECAM:
P
HACTIVE = Desired number of pixels per line of video, not
desired
= 15602
= 0x3CF2
= Desired number of pixels per line of video, includ-
D829BDSA
ing active, sync and blanking.
HSCALE = [ ( 910/P
HSCALE = [ (754 / HACTIVE) – 1] * 4096
HSCALE = [ (922 / HACTIVE) – 1] * 4096
including sync or blanking.
1.7 Video Scaling, Cropping, and Temporal Decimation
HSCALE is programmed with the
desired
desired
) – 1] * 4096
1.0 Functional Description
) – 1] * 4096
CLKx1
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