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authorAndreas Eversberg <jolly@eversberg.eu>2017-11-16 18:16:53 +0100
committerAndreas Eversberg <jolly@eversberg.eu>2017-11-25 19:23:56 +0100
commit40c24a70b2a295073428ec78c281e86a7a84f7ca (patch)
tree4a75eb08b8de76dd982dc5a066006788466e480d /src/common/emphasis.c
parent16194c15f9827edf9cfde9a5c18ccb06353c34a3 (diff)
Restructure: Move emphasis from common code to 'libemphasis'
Diffstat (limited to 'src/common/emphasis.c')
-rw-r--r--src/common/emphasis.c140
1 files changed, 0 insertions, 140 deletions
diff --git a/src/common/emphasis.c b/src/common/emphasis.c
deleted file mode 100644
index 08f944a..0000000
--- a/src/common/emphasis.c
+++ /dev/null
@@ -1,140 +0,0 @@
-/* Pre-Emphasis and De-Emphasis implementation
- *
- * (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
- * All Rights Reserved
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-
-#include <stdio.h>
-#include <stdint.h>
-#include <string.h>
-#include <math.h>
-#include "sample.h"
-#include "../libfilter/iir_filter.h"
-#include "emphasis.h"
-#include "debug.h"
-
-#define PI M_PI
-
-#define CUT_OFF_H 100.0 /* cut-off frequency for high-pass filter */
-#define CUT_OFF_L 4000.0 /* cut-off frequency for low-pass filter */
-
-static void gen_sine(sample_t *samples, int num, int samplerate, double freq)
-{
- int i;
-
- for (i = 0; i < num; i++)
- samples[i] = cos(2.0 * M_PI * freq / (double)samplerate * (double)i);
-}
-
-static double get_level(sample_t *samples, int num)
-{
- int i;
- double envelope = 0;
- for (i = num/2; i < num; i++) {
- if (samples[i] > envelope)
- envelope = samples[i];
- }
-
- return envelope;
-}
-
-int init_emphasis(emphasis_t *state, int samplerate, double cut_off)
-{
- double factor;
- sample_t test_samples[samplerate / 10];
-
- memset(state, 0, sizeof(*state));
-
- /* exp (-2 * PI * CUT_OFF * delta_t) */
- factor = exp(-2.0 * PI * cut_off / (double)samplerate); /* 1/samplerate == delta_t */
-
- PDEBUG(DDSP, DEBUG_DEBUG, "Emphasis factor = %.3f\n", factor);
- state->p.factor = factor;
- state->p.amp = 1.0;
- state->d.factor = factor;
- state->d.amp = 1.0;
-
- /* do not de-emphasis below CUT_OFF_H */
- iir_highpass_init(&state->d.hp, CUT_OFF_H, samplerate, 1);
-
- /* do not pre-emphasis above CUT_OFF_L */
- iir_lowpass_init(&state->p.lp, CUT_OFF_L, samplerate, 1);
-
- /* calibrate amplification to be neutral at 1000 Hz */
- gen_sine(test_samples, sizeof(test_samples) / sizeof(test_samples[0]), samplerate, 1000.0);
- pre_emphasis(state, test_samples, sizeof(test_samples) / sizeof(test_samples[0]));
- state->p.amp = 1.0 / get_level(test_samples, sizeof(test_samples) / sizeof(test_samples[0]));
- gen_sine(test_samples, sizeof(test_samples) / sizeof(test_samples[0]), samplerate, 1000.0);
- de_emphasis(state, test_samples, sizeof(test_samples) / sizeof(test_samples[0]));
- state->d.amp = 1.0 / get_level(test_samples, sizeof(test_samples) / sizeof(test_samples[0]));
-
- return 0;
-}
-
-void pre_emphasis(emphasis_t *state, sample_t *samples, int num)
-{
- double x, y, x_last, factor, amp;
- int i;
-
- iir_process(&state->p.lp, samples, num);
-
- x_last = state->p.x_last;
- factor = state->p.factor;
- amp = state->p.amp;
-
- for (i = 0; i < num; i++) {
- x = *samples;
-
- /* pre-emphasis */
- y = x - factor * x_last;
-
- x_last = x;
-
- *samples++ = amp * y;
- }
-
- state->p.x_last = x_last;
-}
-
-void de_emphasis(emphasis_t *state, sample_t *samples, int num)
-{
- double x, y, y_last, factor, amp;
- int i;
-
- y_last = state->d.y_last;
- factor = state->d.factor;
- amp = state->d.amp;
-
- for (i = 0; i < num; i++) {
- x = *samples;
-
- /* de-emphasis */
- y = x + factor * y_last;
-
- y_last = y;
-
- *samples++ = amp * y;
- }
-
- state->d.y_last = y_last;
-}
-
-/* high pass filter to remove DC and low frequencies */
-void dc_filter(emphasis_t *state, sample_t *samples, int num)
-{
- iir_process(&state->d.hp, samples, num);
-}
-