AL300 datasheet(20/64 Pages) ETC

20 / 64 page

AL300

November 28, 2001

6.8 Zoom Engine

The AL300 has two independent horizontal and vertical scale engines performing proprietary scaling

operations. The range of linear scaling can be from 1 up to 8 times.

The horizontal interpolation coefficient is generated by the 11-bit HRATIO (Reg. #14h and #15h),

which defines the scaling ratio with the 3 MSB as the integer part and the 8 LSB as the mantissa part.

The HRATIO is derived from the size of the displayed input video and the actual scaled display size.

The related registers include CAPHSTART (Reg. #20h and #21h), CAPHEND (Reg. #22h),

DSPHDESTART (Reg. #33h), and DSPHDEEND (Reg. #34h). The initial value for the interpolation

coefficient generator is defined by HINITPHASE (Reg. #18h).

The vertical interpolation coefficient generator, the 15-bit VRATIO (Reg. #16h and #17h) defines the

scaling ratio with the 3 MSB being the integer part and the 12 LSB being the mantissa part. The

VRATIO is derived from the size of the displayed input video and the actual scaled display size. The

registers involved include CAPVSTART (Reg. #24h and #25h), CAPVEND (Reg. #26h and #27h),

DSPVDESTART (Reg. #37h and #38h), and DSPVDEEND (Reg. #39h and #3Ah). The initial value

for the interpolation coefficient generator is defined by VINITPHASE (Reg. #1Ah). All of these

registers can be used to achieve optimum sharpness and smoothness results for different scaling ratios.

6.9 Operating Modes

The AL300 operates in three different modes: non-interlaced zoom mode, de-interlaced zoom mode,

and bypass mode

6.9.1 Non-interlaced Zoom Mode

Non-interlaced zoom mode is for synchronizing the output display with the non-interlaced input video

with a zooming ratio of larger than or equal to one. The output video can have the same or higher

resolution than the input video. First of all, the output timing parameters are decided depending on

the size of the display device. Secondly, the firmware determines what area of picture needs to be

displayed with the help of internal scan rate and position detection circuits.

The input timing

parameters are set accordingly. The next step is to set the parameters of the scaling engine by the

ratio between the output video and input video. Details about programming the related registers can

be found in the Register Definition section.

6.9.2 De-interlaced Zoom Mode

De-interlaced zoom mode is different from Non-interlaced zoom mode in that the input video is

interlaced and needs to be de-interlaced. Some parameters need to be treated differently for different

operations required in odd and even fields in interlaced modes compared to non-interlaced modes.

Details about programming the related registers can be found in the Register Definition section.

AL300 Datasheet(PDF) 20 Page - List of Unclassifed Manufacturers