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Improve slope estimation on start

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The first frames are typically received and decoded with more delay than
the others, causing a wrong slope estimation on start.

To compensate, assume an initial slope of 1, then progressively use the
estimated slope.
This commit is contained in:
Romain Vimont 2021-07-13 23:14:43 +02:00
parent 4c4d02295c
commit 0ae10f2b39
1 changed files with 14 additions and 2 deletions
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16
app/src/clock.c
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@ -19,6 +19,7 @@ static void
sc_clock_estimate(struct sc_clock *clock,
double *out_slope, sc_tick *out_offset) {
assert(clock->count > 1); // two points are necessary
struct sc_clock_point left_avg = {
.system = clock->left_sum.system / (clock->count / 2),
.stream = clock->left_sum.stream / (clock->count / 2),
@ -27,6 +28,19 @@ sc_clock_estimate(struct sc_clock *clock,
.system = clock->right_sum.system / ((clock->count + 1) / 2),
.stream = clock->right_sum.stream / ((clock->count + 1) / 2),
};
double slope = (double) (right_avg.system - left_avg.system)
/ (right_avg.stream - left_avg.stream);
if (clock->count < SC_CLOCK_RANGE) {
/* The first frames are typically received and decoded with more delay
* than the others, causing a wrong slope estimation on start. To
* compensate, assume an initial slope of 1, then progressively use the
* estimated slope. */
slope = (clock->count * slope + (SC_CLOCK_RANGE - clock->count))
/ SC_CLOCK_RANGE;
}
struct sc_clock_point global_avg = {
.system = (clock->left_sum.system + clock->right_sum.system)
/ clock->count,
@ -34,8 +48,6 @@ sc_clock_estimate(struct sc_clock *clock,
/ clock->count,
};
double slope = (double) (right_avg.system - left_avg.system)
/ (right_avg.stream - left_avg.stream);
sc_tick offset = global_avg.system - (sc_tick) (global_avg.stream * slope);
*out_slope = slope;