Em Mon, 15 Dec 2014 14:49:17 +0530
Prashant Laddha <prladdha@xxxxxxxxx> escreveu:
> Replaced Taylor series calculation for (co)sine with a
> look up table (LUT) for sine values.
Kernel has already a LUT for sin/cos at:
include/linux/fixp-arith.h
The best would be to either use it or improve its precision, if the one there
is not good enough.
Regards,
Mauro
>
> Also reworked fixed point implementation to reduce rounding errors.
>
> Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Cc: Antti Palosaari <crope@xxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
>
> 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 | 184 +++++++++++++++++++++++++++
> drivers/media/platform/vivid/vivid-sin.h | 31 +++++
> 4 files changed, 252 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..1f8b328 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;
> + s32 src_phase_inc;
> + s32 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..e3d6149
> --- /dev/null
> +++ b/drivers/media/platform/vivid/vivid-sin.c
> @@ -0,0 +1,184 @@
> +/*
> + * 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..6c8bab2
> --- /dev/null
> +++ b/drivers/media/platform/vivid/vivid-sin.h
> @@ -0,0 +1,31 @@
> +/*
> + * 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
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