1.sin LUT is recomputed with precision of 16 bits to represent
fractional part. (lowest fraction that can be represented now
is 1/2^16, that is 0.000015).
2.Instead of using PI = 22/7 in intermediate calculation, use
precomputed value for 2PI
3 To avoid overflows, use 64 bit variables for intermediate
calculations
Cc: Hans Verkuil <hans.verk...@cisco.com>
Cc: Antti Palosaari <cr...@iki.fi>
Signed-off-by: Prashant Laddha <prlad...@cisco.com>
---
drivers/media/platform/vivid/vivid-core.h | 4 +-
drivers/media/platform/vivid/vivid-sdr-cap.c | 33 +++++-----
drivers/media/platform/vivid/vivid-sin.c | 94 ++++++++++++++++------------
drivers/media/platform/vivid/vivid-sin.h | 9 +--
4 files changed, 78 insertions(+), 62 deletions(-)
diff --git a/drivers/media/platform/vivid/vivid-core.h
b/drivers/media/platform/vivid/vivid-core.h
index 6f4445a..ea5c5c8 100644
--- a/drivers/media/platform/vivid/vivid-core.h
+++ b/drivers/media/platform/vivid/vivid-core.h
@@ -434,8 +434,8 @@ struct vivid_dev {
struct list_head sdr_cap_active;
unsigned sdr_adc_freq;
unsigned sdr_fm_freq;
- int sdr_fixp_src_phase;
- int sdr_fixp_mod_phase;
+ s64 sdr_fixp_src_phase;
+ s64 sdr_fixp_mod_phase;
bool tstamp_src_is_soe;
bool has_crop_cap;
diff --git a/drivers/media/platform/vivid/vivid-sdr-cap.c
b/drivers/media/platform/vivid/vivid-sdr-cap.c
index 1f8b328..1e5abd7 100644
--- a/drivers/media/platform/vivid/vivid-sdr-cap.c
+++ b/drivers/media/platform/vivid/vivid-sdr-cap.c
@@ -429,12 +429,16 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct
vivid_buffer *buf)
u8 *vbuf = vb2_plane_vaddr(&buf->vb, 0);
unsigned long i;
unsigned long plane_size = vb2_plane_size(&buf->vb, 0);
- int fixp_i, fixp_q;
+ s64 fixp_i;
+ s64 fixp_q;
u32 adc_freq;
u32 sig_freq;
- s32 src_phase_inc;
- s32 mod_phase_inc;
+ s64 src_phase_inc;
+ s64 mod_phase_inc;
+ s64 signal_offset = 1275; /* 127.5 would be added modulated signal*/
+
+ signal_offset <<= FIX_PT_PREC;
/*
* TODO: Generated beep tone goes very crackly when sample rate is
@@ -454,30 +458,27 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct
vivid_buffer *buf)
mod_phase_inc = calc_cos(dev->sdr_fixp_src_phase);
dev->sdr_fixp_src_phase += src_phase_inc;
- while (dev->sdr_fixp_src_phase >= ((44 << FIX_PT_PREC)/7))
- dev->sdr_fixp_src_phase -= ((44 << FIX_PT_PREC)/7);
-
- mod_phase_inc <<= FIX_PT_PREC;
- mod_phase_inc /= 1275;
+ while (dev->sdr_fixp_src_phase >= FIX_PT_2PI)
+ dev->sdr_fixp_src_phase -= FIX_PT_2PI;
dev->sdr_fixp_mod_phase += mod_phase_inc;
while (dev->sdr_fixp_mod_phase < 0)
- dev->sdr_fixp_mod_phase += ((44 << FIX_PT_PREC) / 7);
+ dev->sdr_fixp_mod_phase += FIX_PT_2PI;
- while (dev->sdr_fixp_mod_phase >= ((44 << FIX_PT_PREC) / 7))
- dev->sdr_fixp_mod_phase -= ((44 << FIX_PT_PREC) / 7);
+ while (dev->sdr_fixp_mod_phase >= FIX_PT_2PI)
+ dev->sdr_fixp_mod_phase -= FIX_PT_2PI;
fixp_i = calc_sin(dev->sdr_fixp_mod_phase);
fixp_q = calc_cos(dev->sdr_fixp_mod_phase);
/* convert 'fixp float' to u8 */
- /* u8 = X * 127.5f + 127.5f; where X is float [-1.0 / +1.0]
- The values stored in sin look table are pre-multipied with 1275.
- So, only do addition */
+ /* u8 = X * 127.5f + 127.5f; where X is float [-1.0 / +1.0] */
- fixp_i += 1275;
- fixp_q += 1275;
+ fixp_i = fixp_i * 1275 + signal_offset;
+ fixp_q = fixp_q * 1275 + signal_offset;
+ fixp_i >>= FIX_PT_PREC;
+ fixp_q >>= FIX_PT_PREC;
*vbuf++ = DIV_ROUND_CLOSEST(fixp_i, 10);
*vbuf++ = DIV_ROUND_CLOSEST(fixp_q, 10);
}
diff --git a/drivers/media/platform/vivid/vivid-sin.c
b/drivers/media/platform/vivid/vivid-sin.c
index 1ba6df9..24680ea 100644
--- a/drivers/media/platform/vivid/vivid-sin.c
+++ b/drivers/media/platform/vivid/vivid-sin.c
@@ -26,19 +26,23 @@
#define SIN_LUT_SIZE 256
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
+ 0, 1608, 3216, 4821, 6424, 8022, 9616, 11204,
+ 12785, 14359, 15924, 17479, 19024, 20557, 22078, 23586,
+ 25080, 26558, 28020, 29466, 30893, 32303, 33692, 35062,
+ 36410, 37736, 39040, 40320, 41576, 42806, 44011, 45190,
+ 46341, 47464, 48559, 49624, 50660, 51665, 52639, 53581,
+ 54491, 55368, 56212, 57022, 57798, 58538, 59244, 59914,
+ 60547, 61145, 61705, 62228, 62714, 63162, 63572, 63944,
+ 64277, 64571, 64827, 65043, 65220, 65358, 65457, 65516,
+ 65536
};
-static s32 get_sin_val(u32 index)
+static s64 get_sin_val(u32 index)
{
s32 sign = 1;
u32 tab_index;
u32 new_index;
+ s64 result;
new_index = index & 0xFF; /* new_index = index % 256*/
@@ -52,7 +56,12 @@ static s32 get_sin_val(u32 index)
else
tab_index = 64 - (new_index - 64);
- return sign * sin[tab_index];
+ /* If fixed point precision is more than the precision used to compute
+ * sin table (16 bit currently), then multiply sine values */
+
+ result = sin[tab_index] << (FIX_PT_PREC - 16);
+
+ return sign * result;
}
/*
@@ -111,62 +120,67 @@ static s32 get_sin_val(u32 index)
* 4. To improve the precision of fixed point implementations, divisions
* in different calculations are delayed till last operations. Say,
* d0 = phi - n*(2*pi / N)
- * d0 = phi - n * (2 * (22 / 7) / N) , substitute pi = 22 / 7
- * d0 = phi - (n * 44 * N) / 7
*/
-s32 calc_sin(u32 phase)
+s64 calc_sin(u64 phase)
{
- u32 index;
- u32 d0;
- u32 d1;
- s32 result;
+ u64 index;
+ u64 d0;
+ u64 d1;
+ s64 result;
u64 temp0;
u64 temp1;
temp0 = phase * SIN_LUT_SIZE;
- index = (temp0 * 7) / (44 << FIX_PT_PREC);
+ index = temp0 / (u64)(FIX_PT_2PI);
- temp0 = (temp0 * 7) / 44;
- temp1 = index << FIX_PT_PREC;
+ temp1 = index * (u64)(FIX_PT_2PI);
+ temp1 /= SIN_LUT_SIZE;
- d1 = temp0 - temp1;
- d0 = (1 << FIX_PT_PREC) - d1;
+ d1 = phase - temp1;
+ d0 = (1ULL << FIX_PT_PREC) - d1;
result = d0 * get_sin_val(index) + d1 * get_sin_val(index+1);
return result >> FIX_PT_PREC;
}
-s32 calc_cos(u32 phase)
+s64 calc_cos(u64 phase)
{
- u32 index;
- u32 d0;
- u32 d1;
- s32 result;
+ u64 index;
+ u64 d0;
+ u64 d1;
+ s64 result;
u64 temp0;
u64 temp1;
temp0 = phase * SIN_LUT_SIZE;
- index = (temp0 * 7) / (44 << FIX_PT_PREC);
+ index = temp0 / (u64)(FIX_PT_2PI);
- temp0 = (temp0 * 7) / 44;
- temp1 = index << FIX_PT_PREC;
+ temp1 = index * (u64)(FIX_PT_2PI);
+ temp1 /= SIN_LUT_SIZE;
- d1 = temp0 - temp1;
- d0 = (1 << FIX_PT_PREC) - d1;
+ d1 = phase - temp1;
+ d0 = (1ULL << FIX_PT_PREC) - d1;
+
+ index += (SIN_LUT_SIZE / 4); /* offset for cosine values */
- index += 64;
result = d0 * get_sin_val(index) + d1 * get_sin_val(index+1);
+
return result >> FIX_PT_PREC;
}
-u32 phase_per_sample(u32 signal_freq, u32 sampling_freq)
+/* phase increment or decrement per sample is calculated as
+ *
+ * phase covered in 1 cycle = 2.pi
+ * phase_per_sample = 2.pi / num_samples_per_cycle
+ *
+ * num_samples_per_cycle = samples_per_sec
+ * phase_per_sample = (2.pi x cycles_per_sec) / samples_per_sec
+ * */
+
+u64 phase_per_sample(u32 signal_freq, u32 sampling_freq)
{
- /* phase increment or decrement with each sample is given by
- * (2 x Pi x signal frequency)/sampling frequency
- * To get a better accuracy with fixed point implementation we use
- * Pi = 22/7
- * */
- u64 temp = 44 * ((u64)signal_freq << FIX_PT_PREC);
-
- return temp / (7*sampling_freq);
+ u64 cycles_per_sec = signal_freq;
+ u64 samples_per_sec = sampling_freq;
+
+ return (FIX_PT_2PI * cycles_per_sec) / samples_per_sec;
}
diff --git a/drivers/media/platform/vivid/vivid-sin.h
b/drivers/media/platform/vivid/vivid-sin.h
index 6c8bab2..b27a94e 100644
--- a/drivers/media/platform/vivid/vivid-sin.h
+++ b/drivers/media/platform/vivid/vivid-sin.h
@@ -22,10 +22,11 @@
#ifndef _VIVID_SIN_H_
#define _VIVID_SIN_H_
-#define FIX_PT_PREC 16
+#define FIX_PT_PREC (24)
+#define FIX_PT_2PI (0x6487ED5)
-s32 calc_sin(u32 phase);
-s32 calc_cos(u32 phase);
-u32 phase_per_sample(u32 signal_freq, u32 sampling_freq);
+s64 calc_sin(u64 phase);
+s64 calc_cos(u64 phase);
+u64 phase_per_sample(u32 signal_freq, u32 sampling_freq);
#endif
--
1.9.1
--
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