Compandor: Remove unused option for unaffected level

This commit is contained in:
Andreas Eversberg 2018-10-14 13:07:25 +02:00
parent d058927e2d
commit 393e54b817
2 changed files with 9 additions and 21 deletions

View File

@ -32,7 +32,7 @@
#define EXPAND_ATTACK_FACTOR 1.145 /* about 0.57 after 6 dB step up */
#define EXPAND_RECOVERY_FACTOR 0.753 /* about 1.51 after 6 dB step down */
/* Minimum level value to keep state */
/* Minimum level value to keep state (-60 dB) */
#define ENVELOPE_MIN 0.001
/* Maximum level, to prevent sqrt_tab to overflow */
@ -46,7 +46,7 @@ static double sqrt_tab[10000];
* Hopefully this is correct
*
*/
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms, double unaffected_level)
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms)
{
int i;
@ -60,8 +60,6 @@ void init_compandor(compandor_t *state, double samplerate, double attack_ms, dou
state->c.step_down = pow(COMPRESS_RECOVERY_FACTOR, 1000.0 / recovery_ms / samplerate);
state->e.step_up = pow(EXPAND_ATTACK_FACTOR, 1000.0 / attack_ms / samplerate);
state->e.step_down = pow(EXPAND_RECOVERY_FACTOR, 1000.0 / recovery_ms / samplerate);
state->c.unaffected = unaffected_level;
state->e.unaffected = unaffected_level;
// FIXME: make global, not at instance
for (i = 0; i < 10000; i++)
@ -70,19 +68,17 @@ void init_compandor(compandor_t *state, double samplerate, double attack_ms, dou
void compress_audio(compandor_t *state, sample_t *samples, int num)
{
double value, peak, envelope, step_up, step_down, unaffected;
double value, peak, envelope, step_up, step_down;
int i;
step_up = state->c.step_up;
step_down = state->c.step_down;
peak = state->c.peak;
envelope = state->c.envelope;
unaffected = state->c.unaffected;
// printf("envelope=%.4f\n", envelope);
for (i = 0; i < num; i++) {
/* normalize sample value to unaffected level */
value = *samples / unaffected;
value = *samples;
/* 'peak' is the level that raises directly with the signal
* level, but falls with specified recovery rate. */
@ -101,11 +97,9 @@ void compress_audio(compandor_t *state, sample_t *samples, int num)
if (envelope > ENVELOPE_MAX)
envelope = ENVELOPE_MAX;
value = value / sqrt_tab[(int)(envelope / 0.001)];
*samples++ = value / sqrt_tab[(int)(envelope / 0.001)];
//if (i > 47000.0 && i < 48144)
//printf("time=%.4f envelope=%.4fdb, value=%.4f\n", (double)i/48000.0, 20*log10(envelope), value);
*samples++ = value * unaffected;
}
//exit(0);
@ -115,18 +109,16 @@ void compress_audio(compandor_t *state, sample_t *samples, int num)
void expand_audio(compandor_t *state, sample_t *samples, int num)
{
double value, peak, envelope, step_up, step_down, unaffected;
double value, peak, envelope, step_up, step_down;
int i;
step_up = state->e.step_up;
step_down = state->e.step_down;
peak = state->e.peak;
envelope = state->e.envelope;
unaffected = state->e.unaffected;
for (i = 0; i < num; i++) {
/* normalize sample value to 0 DB level */
value = *samples / unaffected;
value = *samples;
/* for comments: see compress_audio() */
if (fabs(value) > peak)
@ -140,9 +132,7 @@ void expand_audio(compandor_t *state, sample_t *samples, int num)
if (envelope < ENVELOPE_MIN)
envelope = ENVELOPE_MIN;
value = value * envelope;
*samples++ = value * unaffected;
*samples++ = value * envelope;
}
state->e.envelope = envelope;

View File

@ -1,14 +1,12 @@
typedef struct compandor {
struct {
double unaffected;
double step_up;
double step_down;
double peak;
double envelope;
} c;
struct {
double unaffected;
double step_up;
double step_down;
double peak;
@ -16,7 +14,7 @@ typedef struct compandor {
} e;
} compandor_t;
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms, double unaffected_level);
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms);
void compress_audio(compandor_t *state, sample_t *samples, int num);
void expand_audio(compandor_t *state, sample_t *samples, int num);