// the prediction quality is decaying from frame to frame.
static double get_prediction_decay_rate(VP9_COMP *cpi,
FIRSTPASS_STATS *next_frame) {
- double prediction_decay_rate;
- double second_ref_decay;
- double mb_sr_err_diff;
-
- // Initial basis is the % mbs inter coded
- prediction_decay_rate = next_frame->pcnt_inter;
-
// Look at the observed drop in prediction quality between the last frame
// and the GF buffer (which contains an older frame).
- mb_sr_err_diff = (next_frame->sr_coded_error - next_frame->coded_error) /
- cpi->common.MBs;
- if (mb_sr_err_diff <= 512.0) {
- second_ref_decay = 1.0 - (mb_sr_err_diff / 512.0);
- second_ref_decay = pow(second_ref_decay, 0.5);
- if (second_ref_decay < 0.85)
- second_ref_decay = 0.85;
- else if (second_ref_decay > 1.0)
- second_ref_decay = 1.0;
- } else {
- second_ref_decay = 0.85;
- }
-
- if (second_ref_decay < prediction_decay_rate)
- prediction_decay_rate = second_ref_decay;
+ const double mb_sr_err_diff = (next_frame->sr_coded_error -
+ next_frame->coded_error) / cpi->common.MBs;
+ const double second_ref_decay = mb_sr_err_diff <= 512.0
+ ? fclamp(pow(1.0 - (mb_sr_err_diff / 512.0), 0.5), 0.85, 1.0)
+ : 0.85;
- return prediction_decay_rate;
+ return MIN(second_ref_decay, next_frame->pcnt_inter);
}
// Function to test for a condition where a complex transition is followed