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Video Scaler v4.0 User Guide
www.xilinx.com
41
UG805 March 1, 2011
Chapter 8
Coefficients
This section describes the coefficients used by both the Vertical and Horizontal filter
portions of the scaler, in terms of number, range, formatting and download procedures.
Coefficient Table
One single size-configurable, block RAM-based, Dual Port RAM block stores all H and V
coefficients combined, and holds different coefficients for luma and chroma as desired.
This coefficient store may be populated with active coefficients as follows:
•
Using the Coefficient Interface (see
Coefficient Interface
).
•
By preloading using a .coe file
Coefficients that are preloaded using a .coe file remain in this memory until they are
overwritten with coefficients loaded by the Coefficient Interface. Consequently, this is not
possible when using Constant mode. Preloading with coefficients allows the user an easy
way of initializing the scaler from power-up.
When using pCore or GPP interfaces, you may want more than one coefficient set from
which to choose. For example, it may be necessary to select different filter responses for
different shrink factors. This is often true when down-scaling by different factors to
eliminate aliasing artifacts. The user may load (or preload using a .coe file) multiple
coefficient sets.
The number of phases for each set may also vary, dependent upon the nature of the
conversion, and how you have elected to generate and partition the coefficients. The
maximum number of phases per set defines the size of the memory required to store them,
and this may have an impact on resource usage. Careful selection of the parameters
max_phases
and
max_coef_sets
is paramount if optimal resource usage is important.
Each coefficient set is allocated an amount of space equal to 2
max_phases
. Max_phases is a
fixed parameter that is defined at compile time. However, it is not necessary for every set
to have that many phases. The number of phases for each set may be different, provided
you indicate how many phases there are in the current set being used, by setting the input
register values
num_h_phases
, and
num_v_phases
accordingly. Without setting these
correctly, invalid coefficients will be selected by the phase accumulators.
Horizontal filter coefficients are stored in the lower half of the coefficient memory. Vertical
filter coefficients are stored in the upper half of the coefficient memory.
For each of the H
and V
sectors, luma coefficients occupy the lower half and chroma coefficients occupy the
upper half. This method simplifies internal addressing. When the chroma format is set to
4:4:4., one set of coefficients will be shared between all three channels (i.e., R, G, and B will
be scaled identically).
Содержание LogiCORE IP
Страница 1: ...LogiCORE IP Video Scaler v4 0 User Guide UG805 March 1 2011...
Страница 6: ...Video Scaler v4 0 User Guide www xilinx com UG805 March 1 2011...
Страница 14: ...14 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Preface About This Guide...
Страница 18: ...18 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 1 Introduction...
Страница 20: ...20 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 2 Overview...
Страница 70: ...70 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 9 Performance...
Страница 74: ...74 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Appendix A Use Cases...
Страница 92: ...92 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Appendix B Programmer Guide...