ref: aa5c1b4c5d80991e4b48dd302d3ec5f1a97552e8
parent: 6d227137221ea4eead9d81daf3d2f0915560bbff
parent: e5112b3ae3352c4c55fb31235305f3f80f4b8f7e
author: paulwilkins <paulwilkins@google.com>
date: Mon May 11 08:28:44 EDT 2015
Merge "Skip the last frame update for some frame repeats."
--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -3420,6 +3420,32 @@
return mask;
}
+#define EXTREME_UNDERSHOOT_RATIO 10
+#define LOW_ABSOLUTE_RATE_PER_MB 2
+static int frame_repeat_detected(VP9_COMP *cpi) {+ RATE_CONTROL *const rc = &cpi->rc;
+ int repeat_detected = 0;
+ int low_rate = LOW_ABSOLUTE_RATE_PER_MB * cpi->common.MBs;
+
+ // Detects an "unexpected frame buffer repeat".
+ // This status is not strictly a frame repeat but is triggered when
+ // a frame hugely undershoots the expected first pass target and in
+ // absolute terms the rate is very low. A typical situation where this may
+ // occurr is if the frame, whilst not matching the previous frame, DOES very
+ // closely match the contents of one of the other frame buffers. A genuinely
+ // static scene should not normally trigger this case as the last frame
+ // will also match and the predicted rate will thus be low.
+ if (!frame_is_kf_gf_arf(cpi) && !cpi->rc.is_src_frame_alt_ref &&
+ rc->projected_frame_size) {+ if ((rc->projected_frame_size < low_rate) &&
+ ((rc->base_frame_target / rc->projected_frame_size) >=
+ EXTREME_UNDERSHOOT_RATIO)) {+ repeat_detected = 1;
+ }
+ }
+ return repeat_detected;
+}
+
static void encode_frame_to_data_rate(VP9_COMP *cpi,
size_t *size,
uint8_t *dest,
@@ -3562,6 +3588,14 @@
cpi->refresh_last_frame = 1;
cm->frame_to_show = get_frame_new_buffer(cm);
+
+ // Test for special case where the frame appears to be a repeat of an earlier
+ // encoded frame buffer but this was not predicted by the first pass.
+ // In this case do not update the last frame buffer.
+ if ((cpi->oxcf.pass == 2) && (frame_is_intra_only(cm) == 0) &&
+ frame_repeat_detected(cpi)) {+ cpi->refresh_last_frame = 0;
+ }
// Pick the loop filter level for the frame.
loopfilter_frame(cpi, cm);