DEVICES INCORPORATED

LF3311

Horizontal / Vertical Digital Image Filter

Improved Performance

LOGIC Devices Incorporated

16

9/19/05 LDS.3311-C

Video Imaging Products

In Orthogonal Mode, the horizontal and vertical filters are used concurrently to implement an orthogonal

kernel on the input data (see Figure 16). The HV Filter can handle kernel sizes of 3-3, 5-5, and 7-7

(see Figure 17). Data delay elements at the input of the horizontal filter and the output of the vertical

filter are used to properly align data so that the orthogonal kernel is implemented correctly. The data

delays are automatically set to the correct lengths based on the programmed length of the line buffers

and the kernel size.

Kernel sizes of 3-3, 5-5, and 7-7 require that the horizontal filter’s output be delayed by LB – 2, 2(LB)

– 3, and 3(LB) – 4 clock cycles respectively before being added to the vertical filter’s output (LB is the

programmed line buffer length). The data delay at the input of the horizontal filter handles the LB, 2(LB),

and 3(LB) delays. The data delay at the output of the vertical filter handles the – 2, – 3, and – 4 delays.

For example, if the line buffers are programmed for a length of 720 and a 5–5 kernel is selected, the

horizontal filter input data delay will be 1440 clock cycles and the vertical filter output data delay will be

3 clock cycles.

It is important to note that the first 3, 5, or 7 multipliers of the horizontal and vertical filters must be used

in Orthogonal Mode. If other multipliers are used, data from the horizontal and vertical filters will not line

up correctly because the data delays are calculated assuming that the first 3, 5, or 7 multipliers are used.

Also, the ALUs in the horizontal filter should be configured to accept data from the forward I/D Register path

into ALU Input A and force ALU Input B to 0.

Operating Modes

Figure 15. 3-3, 5-5, and 7-7 Orthagonal Kernels

Figure 14. Orthogonal Mode

HORIZONTAL FILTER

LINE BUFFER

12

LINE BUFFER

LINE BUFFER

LINE BUFFER

LINE BUFFER

LINE BUFFER

LINE BUFFER

12

DATA

DELAY

DATA

DELAY

Orthogonal Mode