Exploiting the symmetry and repetitive nature of sine waveform
to reduce size of sine LUT. Values up to phase <= pi/4, can be
used to calculate sine for remaining phases.
Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Antti Palosaari <crope@xxxxxx>
Signed-off-by: Prashant Laddha <prladdha@xxxxxxxxx>
---
drivers/media/platform/vivid/vivid-sin.c | 74 ++++++++++++++------------------
1 file changed, 32 insertions(+), 42 deletions(-)
diff --git a/drivers/media/platform/vivid/vivid-sin.c b/drivers/media/platform/vivid/vivid-sin.c
index e3d6149..2ed9f7f 100644
--- a/drivers/media/platform/vivid/vivid-sin.c
+++ b/drivers/media/platform/vivid/vivid-sin.c
@@ -25,46 +25,38 @@
#define SIN_TAB_SIZE 256
- /*TODO- Reduce the size of the table */
-/* Since sinewave is symmetric, it can be represented using only quarter
- of the samples compared to the number of samples used below */
-
-static s32 sin[257] = {
- 0, 31, 63, 94, 125, 156, 187, 218,
- 249, 279, 310, 340, 370, 400, 430, 459,
- 488, 517, 545, 573, 601, 628, 655, 682,
- 708, 734, 760, 784, 809, 833, 856, 879,
- 902, 923, 945, 965, 986, 1005, 1024, 1042,
- 1060, 1077, 1094, 1109, 1124, 1139, 1153, 1166,
- 1178, 1190, 1200, 1211, 1220, 1229, 1237, 1244,
- 1251, 1256, 1261, 1265, 1269, 1272, 1273, 1275,
- 1275, 1275, 1273, 1272, 1269, 1265, 1261, 1256,
- 1251, 1244, 1237, 1229, 1220, 1211, 1200, 1190,
- 1178, 1166, 1153, 1139, 1124, 1109, 1094, 1077,
- 1060, 1042, 1024, 1005, 986, 965, 945, 923,
- 902, 879, 856, 833, 809, 784, 760, 734,
- 708, 682, 655, 628, 601, 573, 545, 517,
- 488, 459, 430, 400, 370, 340, 310, 279,
- 249, 218, 187, 156, 125, 94, 63, 31,
- 0, -31, -63, -94, -125, 156, -187, -218,
- -249, -279, -310, -340, -370, -400, -430, -459,
- -488, -517, -545, -573, -601, -628, -655, -682,
- -708, -734, -760, -784, -809, -833, -856, -879,
- -902, -923, -945, -965, -986, -1005, -1024, -1042,
- -1060, -1077, -1094, -1109, -1124, -1139, -1153, -1166,
- -1178, -1190, -1200, -1211, -1220, -1229, -1237, -1244,
- -1251, -1256, -1261, -1265, -1269, -1272, -1273, -1275,
- -1275, -1275, -1273, -1272, -1269, -1265, -1261, -1256,
- -1251, -1244, -1237, -1229, -1220, -1211, -1200, -1190,
- -1178, -1166, -1153, -1139, -1124, -1109, -1094, -1077,
- -1060, -1042, -1024, -1005, -986, -965, -945, -923,
- -902, -879, -856, -833, -809, -784, -760, -734,
- -708, -682, -655, -628, -601, -573, -545, -517,
- -488, -459, -430, -400, -370, -340, -310, -279,
- -249, -218, -187, -156, -125, -94, -63, -31,
- 0
+static s32 sin[65] = {
+ 0, 31, 63, 94, 125, 156, 187, 218, 249, 279, 310, 340,
+ 370, 400, 430, 459, 488, 517, 545, 573, 601, 628, 655, 682,
+ 708, 734, 760, 784, 809, 833, 856, 879, 902, 923, 945, 965,
+ 986, 1005, 1024, 1042, 1060, 1077, 1094, 1109, 1124, 1139, 1153, 1166,
+ 1178, 1190, 1200, 1211, 1220, 1229, 1237, 1244, 1251, 1256, 1261, 1265,
+ 1269, 1272, 1273, 1275, 1275
};
+static s32 get_sin_val(u32 index)
+{
+ u32 tab_index;
+ u32 new_index;
+
+ if (index <= 64)
+ return sin[index];
+ else if (index > 64 && index <= 128) {
+ tab_index = 64 - (index - 64);
+ return sin[tab_index];
+ } else if (index > 128 && index <= 192) {
+ tab_index = index - 128;
+ return (-1) * sin[tab_index];
+ } else if (index > 192 && index <= 255) {
+ tab_index = 64 - (index - 192);
+ return (-1) * sin[tab_index];
+ }
+
+ new_index = index % 256;
+ return get_sin_val(new_index);
+
+}
+
/*
* Calculation of sine is implemented using a look up table for range of
* phase values from 0 to 2*pi. Look table contains finite entries, say N.
@@ -142,8 +134,7 @@ s32 calc_sin(u32 phase)
d1 = temp0 - temp1;
d0 = (1 << FIX_PT_PREC) - d1;
- result = (d0 * sin[index % 256] + d1 * sin[(index+1)%256]);
-
+ result = d0 * get_sin_val(index) + d1 * get_sin_val(index+1);
return result >> FIX_PT_PREC;
}
@@ -166,8 +157,7 @@ s32 calc_cos(u32 phase)
d0 = (1 << FIX_PT_PREC) - d1;
index += 64;
- result = (d0 * sin[index % 256] + d1 * sin[(index+1)%256]);
-
+ result = d0 * get_sin_val(index) + d1 * get_sin_val(index+1);
return result >> FIX_PT_PREC;
}
--
1.9.1
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