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[media] vivid sdr: Use LUT based implementation for sin/cos()

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The common implementation for sin/cos in include/linux/fixp-arith.h
has been improved recently to provide higher precision.

Replacing native implementation of sin/cos in vivid sdr with common
implementation. This serves two purposes:

1. Improved accuracy: the native implementation based on the Taylor
   series is more prone to rounding errors.
2. Reuse of common function: this is better compared to maintaining
   native versions for each driver.

Suggested by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Prashant Laddha 2015-02-04 06:07:31 -03:00 committed by Mauro Carvalho Chehab
parent 559addc25b
commit 4e30a37345
1 changed files with 27 additions and 39 deletions
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66
drivers/media/platform/vivid/vivid-sdr-cap.c
View File

@ -27,6 +27,7 @@
#include <media/v4l2-common.h>
#include <media/v4l2-event.h>
#include <media/v4l2-dv-timings.h>
#include <linux/fixp-arith.h>
#include "vivid-core.h"
#include "vivid-ctrls.h"
@ -423,40 +424,19 @@ 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));
}
#define FIXP_N (15)
#define FIXP_FRAC (1 << FIXP_N)
#define FIXP_2PI ((int)(2 * 3.141592653589 * FIXP_FRAC))
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;
s32 src_phase_step;
s32 mod_phase_step;
s32 fixp_i;
s32 fixp_q;
/*
* TODO: Generated beep tone goes very crackly when sample rate is
@ -466,28 +446,36 @@ 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,
src_phase_step = DIV_ROUND_CLOSEST(FIXP_2PI * BEEP_FREQ,
dev->sdr_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;
mod_phase_step = fixp_cos32_rad(dev->sdr_fixp_src_phase,
FIXP_2PI) >> (31 - FIXP_N);
dev->sdr_fixp_src_phase += src_phase_step;
dev->sdr_fixp_mod_phase += mod_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);
while (dev->sdr_fixp_mod_phase < FIXP_2PI)
dev->sdr_fixp_mod_phase += FIXP_2PI;
while (dev->sdr_fixp_mod_phase > FIXP_2PI)
dev->sdr_fixp_mod_phase -= FIXP_2PI;
while (dev->sdr_fixp_src_phase > (2 * FIXP_PI))
dev->sdr_fixp_src_phase -= (2 * FIXP_PI);
while (dev->sdr_fixp_src_phase > FIXP_2PI)
dev->sdr_fixp_src_phase -= FIXP_2PI;
fixp_i = fixp_cos(dev->sdr_fixp_mod_phase);
fixp_q = fixp_sin(dev->sdr_fixp_mod_phase);
fixp_i = fixp_cos32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
fixp_q = fixp_sin32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
/* Normalize fraction values represented with 32 bit precision
* to fixed point representation with FIXP_N bits */
fixp_i >>= (31 - FIXP_N);
fixp_q >>= (31 - FIXP_N);
/* convert 'fixp float' to u8 */
/* u8 = X * 127.5f + 127.5f; where X is float [-1.0 / +1.0] */