+
+// Check if we should resize, based on average QP from past x frames.
+// Only allow for resize at most one scale down for now, scaling factor is 2.
+int vp9_resize_one_pass_cbr(VP9_COMP *cpi) {
+ const VP9_COMMON *const cm = &cpi->common;
+ RATE_CONTROL *const rc = &cpi->rc;
+ int resize_now = 0;
+ cpi->resize_scale_num = 1;
+ cpi->resize_scale_den = 1;
+ // Don't resize on key frame; reset the counters on key frame.
+ if (cm->frame_type == KEY_FRAME) {
+ cpi->resize_avg_qp = 0;
+ cpi->resize_count = 0;
+ return 0;
+ }
+ // Resize based on average QP over some window.
+ // Ignore samples close to key frame, since QP is usually high after key.
+ if (cpi->rc.frames_since_key > 2 * cpi->framerate) {
+ const int window = 5 * cpi->framerate;
+ cpi->resize_avg_qp += cm->base_qindex;
+ if (cpi->rc.buffer_level < 0)
+ ++cpi->resize_buffer_underflow;
+ ++cpi->resize_count;
+ // Check for resize action every "window" frames.
+ if (cpi->resize_count == window) {
+ int avg_qp = cpi->resize_avg_qp / cpi->resize_count;
+ // Resize down if buffer level has underflowed sufficent amount in past
+ // window, and we are at original resolution.
+ // Resize back up if average QP is low, and we are currently in a resized
+ // down state.
+ if (cpi->resize_state == 0 &&
+ cpi->resize_buffer_underflow > (cpi->resize_count >> 3)) {
+ resize_now = 1;
+ } else if (cpi->resize_state == 1 &&
+ avg_qp < 40 * cpi->rc.worst_quality / 100) {
+ resize_now = -1;
+ }
+ // Reset for next window measurement.
+ cpi->resize_avg_qp = 0;
+ cpi->resize_count = 0;
+ cpi->resize_buffer_underflow = 0;
+ }
+ }
+ // If decision is to resize, reset some quantities, and check is we should
+ // reduce rate correction factor,
+ if (resize_now != 0) {
+ int target_bits_per_frame;
+ int active_worst_quality;
+ int qindex;
+ int tot_scale_change;
+ // For now, resize is by 1/2 x 1/2.
+ cpi->resize_scale_num = 1;
+ cpi->resize_scale_den = 2;
+ tot_scale_change = (cpi->resize_scale_den * cpi->resize_scale_den) /
+ (cpi->resize_scale_num * cpi->resize_scale_num);
+ // Reset buffer level to optimal, update target size.
+ rc->buffer_level = rc->optimal_buffer_level;
+ rc->bits_off_target = rc->optimal_buffer_level;
+ rc->this_frame_target = calc_pframe_target_size_one_pass_cbr(cpi);
+ // Reset cyclic refresh parameters.
+ if (cpi->oxcf.aq_mode == CYCLIC_REFRESH_AQ && cm->seg.enabled)
+ vp9_cyclic_refresh_reset_resize(cpi);
+ // Get the projected qindex, based on the scaled target frame size (scaled
+ // so target_bits_per_mb in vp9_rc_regulate_q will be correct target).
+ target_bits_per_frame = (resize_now == 1) ?
+ rc->this_frame_target * tot_scale_change :
+ rc->this_frame_target / tot_scale_change;
+ active_worst_quality = calc_active_worst_quality_one_pass_cbr(cpi);
+ qindex = vp9_rc_regulate_q(cpi,
+ target_bits_per_frame,
+ rc->best_quality,
+ active_worst_quality);
+ // If resize is down, check if projected q index is close to worst_quality,
+ // and if so, reduce the rate correction factor (since likely can afford
+ // lower q for resized frame).
+ if (resize_now == 1 &&
+ qindex > 90 * cpi->rc.worst_quality / 100) {
+ rc->rate_correction_factors[INTER_NORMAL] *= 0.85;
+ }
+ // If resize is back up, check if projected q index is too much above the
+ // current base_qindex, and if so, reduce the rate correction factor
+ // (since prefer to keep q for resized frame at least close to previous q).
+ if (resize_now == -1 &&
+ qindex > 130 * cm->base_qindex / 100) {
+ rc->rate_correction_factors[INTER_NORMAL] *= 0.9;
+ }
+ }
+ return resize_now;
+}