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alsa: add dll to estimate clock drift

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Make delay signed in the clock io so that we can simply add it to the
tick to get the hw position.
Add clock drift to clock info
This commit is contained in:
Wim Taymans 2018-11-09 15:24:24 +01:00
parent 7925aed863
commit e69cf24f24
8 changed files with 98 additions and 46 deletions
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39
spa/plugins/alsa/alsa-utils.h
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@ -30,6 +30,7 @@ extern "C" {
#endif
#include <stddef.h>
#include <math.h>
#include <asoundlib.h>
@ -63,6 +64,12 @@ struct buffer {
struct spa_list link;
};
struct dll {
double T;
double b, c;
double n0;
};
struct state {
struct spa_handle handle;
struct spa_node node;
@ -86,6 +93,8 @@ struct state {
bool have_format;
struct spa_audio_info current_format;
struct dll dll;
double bw;
snd_pcm_uframes_t buffer_frames;
snd_pcm_uframes_t period_frames;
@ -136,6 +145,36 @@ int spa_alsa_close(struct state *state);
int spa_alsa_write(struct state *state, snd_pcm_uframes_t silence);
static inline void dll_bandwidth(struct dll *dll, double period, double rate, double bandwidth)
{
double w = 2 * M_PI * bandwidth * period / rate;
dll->b = 1.0 - exp(-M_SQRT2 * w);
dll->c = (1.0 - exp(-w * w)) / period;
}
static inline void dll_init(struct dll *dll, double period, double rate, double bandwidth)
{
dll->T = 1000000.0 / rate;
dll->n0 = 0.0;
dll_bandwidth(dll, period, rate, bandwidth);
}
static inline double dll_update(struct dll *dll, double system_time, double period)
{
double e;
if (dll->n0 == 0.0) {
dll->n0 = system_time;
} else {
dll->n0 += period * dll->T;
e = system_time - dll->n0;
dll->n0 += dll->b * e;
dll->T += dll->c * e;
}
return dll->n0;
}
#ifdef __cplusplus
} /* extern "C" */
#endif