Replaced Taylor series calculation with a look up table based
calculation of (co)sine values. Also reworked fixed point
implementation to reduce rounding errors.
Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Antti Palosaari <crope@xxxxxx>
Signed-off-by: Prashant Laddha <prladdha@xxxxxxxxx>
---
drivers/media/platform/vivid/Makefile | 2 +-
drivers/media/platform/vivid/vivid-sdr-cap.c | 87 ++++++--------
drivers/media/platform/vivid/vivid-sin.c | 171 +++++++++++++++++++++++++++
drivers/media/platform/vivid/vivid-sin.h | 30 +++++
4 files changed, 238 insertions(+), 52 deletions(-)
create mode 100644 drivers/media/platform/vivid/vivid-sin.c
create mode 100644 drivers/media/platform/vivid/vivid-sin.h
diff --git a/drivers/media/platform/vivid/Makefile b/drivers/media/platform/vivid/Makefile
index 756fc12..9d5fe1c 100644
--- a/drivers/media/platform/vivid/Makefile
+++ b/drivers/media/platform/vivid/Makefile
@@ -2,5 +2,5 @@ vivid-objs := vivid-core.o vivid-ctrls.o vivid-vid-common.o vivid-vbi-gen.o \
vivid-vid-cap.o vivid-vid-out.o vivid-kthread-cap.o vivid-kthread-out.o \
vivid-radio-rx.o vivid-radio-tx.o vivid-radio-common.o \
vivid-rds-gen.o vivid-sdr-cap.o vivid-vbi-cap.o vivid-vbi-out.o \
- vivid-osd.o vivid-tpg.o vivid-tpg-colors.o
+ vivid-osd.o vivid-tpg.o vivid-tpg-colors.o vivid-sin.o
obj-$(CONFIG_VIDEO_VIVID) += vivid.o
diff --git a/drivers/media/platform/vivid/vivid-sdr-cap.c b/drivers/media/platform/vivid/vivid-sdr-cap.c
index 4af55f1..99fc2c7 100644
--- a/drivers/media/platform/vivid/vivid-sdr-cap.c
+++ b/drivers/media/platform/vivid/vivid-sdr-cap.c
@@ -31,6 +31,7 @@
#include "vivid-core.h"
#include "vivid-ctrls.h"
#include "vivid-sdr-cap.h"
+#include "vivid-sin.h"
static const struct v4l2_frequency_band bands_adc[] = {
{
@@ -423,40 +424,17 @@ int vidioc_g_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
return 0;
}
-#define FIXP_FRAC (1 << 15)
-#define FIXP_PI ((int)(FIXP_FRAC * 3.141592653589))
-
-/* cos() from cx88 driver: cx88-dsp.c */
-static s32 fixp_cos(unsigned int x)
-{
- u32 t2, t4, t6, t8;
- u16 period = x / FIXP_PI;
-
- if (period % 2)
- return -fixp_cos(x - FIXP_PI);
- x = x % FIXP_PI;
- if (x > FIXP_PI/2)
- return -fixp_cos(FIXP_PI/2 - (x % (FIXP_PI/2)));
- /* Now x is between 0 and FIXP_PI/2.
- * To calculate cos(x) we use it's Taylor polinom. */
- t2 = x*x/FIXP_FRAC/2;
- t4 = t2*x/FIXP_FRAC*x/FIXP_FRAC/3/4;
- t6 = t4*x/FIXP_FRAC*x/FIXP_FRAC/5/6;
- t8 = t6*x/FIXP_FRAC*x/FIXP_FRAC/7/8;
- return FIXP_FRAC-t2+t4-t6+t8;
-}
-
-static inline s32 fixp_sin(unsigned int x)
-{
- return -fixp_cos(x + (FIXP_PI / 2));
-}
-
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_src_phase_step, fixp_i, fixp_q;
+ int fixp_i, fixp_q;
+
+ u32 adc_freq;
+ u32 sig_freq;
+ u32 src_phase_inc;
+ u32 mod_phase_inc;
/*
* TODO: Generated beep tone goes very crackly when sample rate is
@@ -466,34 +444,41 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
/* calculate phase step */
#define BEEP_FREQ 1000 /* 1kHz beep */
- fixp_src_phase_step = DIV_ROUND_CLOSEST(2 * FIXP_PI * BEEP_FREQ,
- dev->sdr_adc_freq);
+
+ adc_freq = dev->sdr_adc_freq; /* samples per sec*/
+ sig_freq = BEEP_FREQ; /* cycles per sec */
+ src_phase_inc = phase_per_sample(sig_freq, adc_freq);
for (i = 0; i < plane_size; i += 2) {
- dev->sdr_fixp_mod_phase += fixp_cos(dev->sdr_fixp_src_phase);
- dev->sdr_fixp_src_phase += fixp_src_phase_step;
- /*
- * Transfer phases to [0 / 2xPI] in order to avoid variable
- * overflow and make it suitable for cosine implementation
- * used, which does not support negative angles.
- */
- while (dev->sdr_fixp_mod_phase < (0 * FIXP_PI))
- dev->sdr_fixp_mod_phase += (2 * FIXP_PI);
- while (dev->sdr_fixp_mod_phase > (2 * FIXP_PI))
- dev->sdr_fixp_mod_phase -= (2 * FIXP_PI);
+ 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;
+
+ 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);
- while (dev->sdr_fixp_src_phase > (2 * FIXP_PI))
- dev->sdr_fixp_src_phase -= (2 * FIXP_PI);
+ while(dev->sdr_fixp_mod_phase >= ((44 << FIX_PT_PREC)/7))
+ dev->sdr_fixp_mod_phase -= ((44 << FIX_PT_PREC)/7);
- fixp_i = fixp_cos(dev->sdr_fixp_mod_phase);
- fixp_q = fixp_sin(dev->sdr_fixp_mod_phase);
+ 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] */
- fixp_i = fixp_i * 1275 + FIXP_FRAC * 1275;
- fixp_q = fixp_q * 1275 + FIXP_FRAC * 1275;
- *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
- *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
+ /* 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 */
+
+ fixp_i += 1275;
+ fixp_q += 1275;
+ *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
new file mode 100644
index 0000000..5bd6677
--- /dev/null
+++ b/drivers/media/platform/vivid/vivid-sin.c
@@ -0,0 +1,171 @@
+/*
+ * vivid-sin.c - software defined radio support functions.
+ *
+ * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+
+#include "vivid-sin.h"
+
+#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
+ };
+
+/*
+ * 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.
+ *
+ * Since sinusoid are periodic with period 2*pi, look table stores entries
+ * for phase values from 0 to 2*pi.
+ *
+ * The interval [0,2*pi] is divided into N equal intervals, each representing
+ * a phase increment of (2*pi/N)
+ *
+ * The index 'n' in look up table stores sine value for phase (2*pi*n/N) as -
+ * sin_tab[N] = {sin(0), sin(1*(2*pi/N)),sin(2*(2*pi/N)), ..., sin(N*(2*pi/N))}
+ *
+ |---------|---------|---------|---- . . . .|---------| . . . . |---------|
+ 0 (2*pi/N) (2*2*pi/N) (3*2*pi/N) (n*2*pi/N) 2*pi
+ *
+ * Generation of sine waveform with different frequencies -
+ *
+ * Consider a sine tone with frequency 'f', so,
+ * num_cycles_per_sec = f
+ * Let sampling frequency be 'Fs' so,
+ * num_samples_per_sec = Fs
+ * So, num_samples_per_cycle = Fs/f
+ * Let Nc = Fs/f
+ *
+ * That is, number of samples during one interval of 0 tp 2*pi = Nc, each
+ * sample represents a phase increment of (2*pi/Nc = 2*pi*f/Fs).
+ *
+ * So, for "k" th sample the phase, phi = k*(2*pi/Nc)
+ *
+ * The sine value at phase increments of (2*pi/Nc) is calculated by interpolating
+ * two adjecent samples from sine look table
+ *
+ * As an example, sine value for phase (phi) is calculated below
+ *
+ * 1. Find the interval [(n*2*pi/N), ((n+1)*2*pi/N)] to which phi belongs
+
+ 0 (2*pi/N) (n*2*pi/N) ((n+1)*2*pi/N) 2*pi
+ |---------| . . . . . |---------|---------| . . . . . |---------|
+ ^
+ d0---->|<--d1
+ |
+ phi = k*(2*pi/Nc)
+
+ * For phase (phi) the index n in sine table is given by (phi)/(2*pi/N)
+ * n = integer part of ( phi / (2*pi/N) )
+ *
+ * 2. Find distance d0 and d1 using fractional arithmatic.
+ * d0 = phi - n*(2*pi/N),
+ * d1 = 2*pi/N - d0
+ *
+ * 3. The calculations of fractions are done using fixed point implementation
+ *
+ * 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)
+{
+ u32 index;
+ u32 d0;
+ u32 d1;
+ s32 result;
+ u64 temp0;
+ u64 temp1;
+
+ temp0 = phase * SIN_TAB_SIZE;
+ index = (temp0 * 7) /(44 << FIX_PT_PREC);
+
+ temp0 = (temp0 * 7) /44;
+ temp1 = index << FIX_PT_PREC;
+
+ d1 = temp0 - temp1;
+ d0 = (1 << FIX_PT_PREC) - d1;
+
+ result = (d0 * sin[index % 256] + d1 * sin[(index+1)%256]);
+
+ return result >> FIX_PT_PREC;
+}
+
+s32 calc_cos(u32 phase)
+{
+ u32 index;
+ u32 d0;
+ u32 d1;
+ s32 result;
+ u64 temp0;
+ u64 temp1;
+
+ temp0 = phase * SIN_TAB_SIZE;
+ index = (temp0 * 7) /(44 << FIX_PT_PREC);
+
+ temp0 = (temp0 * 7) /44;
+ temp1 = index << FIX_PT_PREC;
+
+ d1 = temp0 - temp1;
+ d0 = (1 << FIX_PT_PREC) - d1;
+
+ index += 64;
+ result = (d0 * sin[index % 256] + d1 * sin[(index+1)%256]);
+
+ return result >> FIX_PT_PREC;
+}
+
+u32 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);
+}
diff --git a/drivers/media/platform/vivid/vivid-sin.h b/drivers/media/platform/vivid/vivid-sin.h
new file mode 100644
index 0000000..2f77d64
--- /dev/null
+++ b/drivers/media/platform/vivid/vivid-sin.h
@@ -0,0 +1,30 @@
+/*
+ * vivid-sin.h - support functions used to generate (co)sine waveforms for
+ * software defined radio.
+ *
+ * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef _VIVID_SIN_H_
+#define _VIVID_SIN_H_
+
+#define FIX_PT_PREC 16
+
+s32 calc_sin(u32 phase);
+s32 calc_cos(u32 phase);
+u32 phase_per_sample(u32 signal_freq, u32 sampling_freq);
+
+#endif
--
1.9.1
--
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