Improve slope estimation on start
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.
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1 changed files with 14 additions and 2 deletions
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@ -19,6 +19,7 @@ static void
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sc_clock_estimate(struct sc_clock *clock,
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double *out_slope, sc_tick *out_offset) {
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assert(clock->count > 1); // two points are necessary
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struct sc_clock_point left_avg = {
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.system = clock->left_sum.system / (clock->count / 2),
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.stream = clock->left_sum.stream / (clock->count / 2),
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@ -27,6 +28,19 @@ sc_clock_estimate(struct sc_clock *clock,
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.system = clock->right_sum.system / ((clock->count + 1) / 2),
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.stream = clock->right_sum.stream / ((clock->count + 1) / 2),
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};
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double slope = (double) (right_avg.system - left_avg.system)
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/ (right_avg.stream - left_avg.stream);
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if (clock->count < SC_CLOCK_RANGE) {
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/* The first frames are typically received and decoded with more delay
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* than the others, causing a wrong slope estimation on start. To
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* compensate, assume an initial slope of 1, then progressively use the
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* estimated slope. */
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slope = (clock->count * slope + (SC_CLOCK_RANGE - clock->count))
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/ SC_CLOCK_RANGE;
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}
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struct sc_clock_point global_avg = {
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.system = (clock->left_sum.system + clock->right_sum.system)
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/ clock->count,
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@ -34,8 +48,6 @@ sc_clock_estimate(struct sc_clock *clock,
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/ clock->count,
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};
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double slope = (double) (right_avg.system - left_avg.system)
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/ (right_avg.stream - left_avg.stream);
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sc_tick offset = global_avg.system - (sc_tick) (global_avg.stream * slope);
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*out_slope = slope;
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