Table of Contents
Advertisement
MB86R02 'Jade-D' Hardware Manual V1.64
18.7.4 Scaling
18.7.4.1
Downscaling Function
If the CM (Capture Mode) bits of the video capture mode register (VCM) are set to 11, the capture
controller reduces the incoming video size. The amount of reduction can be set independently in both
vertical and horizontal axes whereby the units used for the calculation are different (!). The reduction is
determined per line on the vertical axis and in 2-pixel units on the horizontal axis. The scale factors
are defined by seperate 16-bit fractional values (filter coefficients), whereby the integer part of each is
represented by 5 bits and the fractional part is represented by 11 bits. Valid setting values range from
0800
to FFFF
. The vertical scaling factor is determined using the filter coefficient set in the VSCF
H
H
and VSCI bitfields of the capture scale register (CSC). The horizontal scaling factor is set using the
filter coefficient set in the bitfields HSCI and HSCF of the same register. The default value of the
register is 08000800
(0x800 = 2048 therefore – using the formula shown below - 1:1 scaling, i.e. no
H
scaling). An example of the settings required for vertical and horizontal reduction is shown below:
(2048 is a hardware fixed value!)
Reduction in vertical direction:
576 → 490 lines: 576/490 = ratio of 1.176
1.176 × 2048 = 2408 (= filter coefficient of 0x0968 in hexadecimal)
Reduction in horizontal direction:
720 → 648 pixels: 720/648 = ratio of 1.111
1.111 × 2048 = 2275 (= filter coefficient of 0x08E3 in hexadecimal)
The result to be set in the
The capture horizontal pixel (CHP) and capture vertical pixel (CVP) registers are used to limit the
number of pixels output after scaling. Note that they are not used to set scaling values. Pixels that
exceed the values set in the
the defaults of these registers are used.
18.7.4.2
Upscaling Function
The capture controller is able to increase the size of a video capture picture by a factor of 2 in both
horizontal and vertical directions. This feature can be used to achieve the full-screen display of input
video streams which have a resolution which is less than the actual display size. In order to use the
up-scaling mode, the horizontal and vertical factor must be less than one.
Do not specify different scaling modes (downscaling/upscaling) for the horizontal and vertical factors!
Also initialize the following registers as follows:
Set the 'Magnify Scaling' bit (L1DM) in the L1EM register (L1 extended mode) register of the
display controller to '10'.
In the
CMSS
(Capture Magnify Source Size) register, set the source picture size (i.e. original,
prior to upscaling) using the CMSHP and CMSVL bitfields.
In the
CMDS
(Capture Magnify Display Size) register, set the final picture size (i.e. upscaled
after processing) using the CMDHP and CMDVL bitfields.
CSC
register is therefore: 096808E3
CHP
and
CVP
registers are simply dropped (clamp processing). Usually,
H
CSC
18-43
Advertisement
Table of Contents
