Analog Devices ADV8003, Руководство по оборудованию

Страница: 158 / 440

ADV8003 Hardware Manual
Rev. B, August 2013 158
3.2.2.2. Horizontal Down Scaler
Although the VOM has both horizontal and vertical scalers, there is also a horizontal down scaler in the VIM. The purpose of the VIM
down scaler is to save external memory bandwidth by doing horizontal downscaling before writing video data into the external memory
to save memory bandwidth.
The down scaler in the VIM should only be enabled when horizontal downscaling is needed, which means that the number of horizontal
output active pixels should be less than the number of horizontal input active pixels. When album mode is enabled, the specified active
output video width should be the album width.
If the horizontal resolution of the PVSP output timing is less than the input timing, the horizontal down scaler can be enabled to reduce
the load on the external DDR2 memory. This horizontal down scaler input resolution is defined by the
pvsp_vim_crop_width[10:0]
register and the output resolution is defined by the pvsp_vim_d_scal_out_width[10:0] register. To enable the horizontal down scaler,
pvsp_vim_d_scal_enable should be set to 1.
pvsp_vim_d_scal_enable , Primary VSP Map, Address 0xE883[5]
This bit is used to enable the VIM down scaler.
Function
pvsp_vim_d_scal_enabl
e Description
0  Disable VIM down scaler
1 Enable VIM down scaler
pvsp_vim_d_scal_out_width[10:0]
, Primary VSP Map,
Address 0xE83A[2:0]; Address 0xE83B[7:0]
This signal is used to set the output video width of the down-scaling scaler in the VIM. The input video width is set by register
pvsp_vim_crop_width. If VIM crop is not enabled, pvsp_vim_crop_width is auto configured by pvsp_autocfg_input_vid, which is the
same with input video's horizontal resolution.
Function
pvsp_vim_d_scal_out_
width[10:0] Description
0x000  Default
0xXXX Output width of VIM scalar
3.2.2.3. Scaler Interpolation Mode
This section describes the method for scaling the input video data. The purpose of the scaler is to allow different input formats to be
displayed on a screen with a fixed resolution. The VIM scaler is usually used for downscaling, for example, 1080p to be downscaled to a
lower definition format such as 480p. Different scaling interpolation modes will affect scaler performance. The options for video scaling
modes are described below and are chosen using
pvsp_vim_scal_type[1:0] .
Proprietary ADI Algorithm
This is a custom algorithm developed by ADI which allows improved performance in the scaling of the input video. This can reduce many
common artifacts when scaling video data such as:
• Saw tooth – otherwise known as ‘jaggies’, this is an artifact that occurs when an image is zoomed in and is one of the most
important criteria when evaluating scaling performance.
• Edge blurring – when zooming in, most high frequency information is lost, resulting in edges becoming blurred. The
proprietary ADI algorithm keeps the edge region sharp by retaining the high frequency information.
• Ringing – also known as the Gibbs phenomenon, can be found on video due to a reduction in high frequency information. The
proprietary ADI algorithm helps with the reduction of such artifacts.