Commit Graph

2 Commits

Author SHA1 Message Date
Lajos Molnar
c0c1cfcb57 OMAPDSS: DISPC: Fix FIR coefficients
coef3_M8 had an incorrect phase with 50% more intensity. This resulted in
banding on slightly down/upscaled images. Fixed a rounding error in coef5_M9.

Also removed ARRAY_LEN macro as ARRAY_SIZE is the standard linux one.

Signed-off-by: Lajos Molnar <lajos@ti.com>
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
2012-03-06 14:08:23 +02:00
Chandrabhanu Mahapatra
debd90749b OMAPDSS: DISPC: Update Fir Coefficients
The FIR coefficients present in kernel are being updated to new coefficients
consisting of 24 coefficient tables, with 12 each for 3 tap and 5 tap scenario,
which are chosen on the basis of DISPC up/downsampling filters M value. M is
the inverse of low pass cut off frequency of the sampling filter. For vertical
scaling 3 tap or 5 tap tables are used based on the clock rate and width of
the line buffer whereas in OMAP2 3 tap is always used. For horizontal scaling
however 5 tap tables are always used.

New coefficients and the corresponding logic have been tested on OMAP2, OMAP3
and OMAP4. Horizontal and vertical scaling worked fine except for some 3 tap
vs 5 tap issue during vertical upscaling and clock failing issues which is
acknowledged in the next patch. Vertical upscaling was found to perform better
under 5 taps. The 24 coefficient tables have been moved to another file
dispc_coefs.c for proper maintainance.

This code is written based on code written by Lajos Molnar <lajos@ti.com> in
Android Kernel for scaling. Lajos Molnar <lajos@ti.com> had fine tuned the FIR
coefficient selection process and reduced outliness and blockiness around
images when upscaling more than 2 times.

Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
2012-01-02 08:51:29 +02:00