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>
Signed-off-by: Prashant Laddha <prladdha@xxxxxxxxx>
---
drivers/media/platform/vivid/vivid-sin.c | 49 ++++++++++++++++----------------
1 file changed, 24 insertions(+), 25 deletions(-)
diff --git a/drivers/media/platform/vivid/vivid-sin.c b/drivers/media/platform/vivid/vivid-sin.c
index 5bd6677..0774bdd 100644
--- a/drivers/media/platform/vivid/vivid-sin.c
+++ b/drivers/media/platform/vivid/vivid-sin.c
@@ -24,35 +24,34 @@
#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,
+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, 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
+ 1269, 1272, 1273, 1275, 1275
};
+static s32 get_sin_val(u32 index)
+{
+ if(index <= 64)
+ return sin[index];
+ else if (index > 64 && index <= 128) {
+ u32 tab_index = 64 - (index - 64);
+ return sin[tab_index];
+ } else if (index > 128 && index <= 192) {
+ u32 tab_index = index - 128;
+ return (-1) * sin[tab_index];
+ } else if (index > 192 && index <= 255) {
+ u32 tab_index = 64 - (index - 192);
+ return (-1) * sin[tab_index];
+ } else {
+ u32 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.
@@ -130,7 +129,7 @@ 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;
}
@@ -154,7 +153,7 @@ 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
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
