Improved coding for static content.
Use a much better 'q' for the 1st (unforced) keyframes.
This vastly improves PSNR for static content like slideshows, audio-only
music videos with static thumbnails etc.
Exactly neutral on regular videos like lowres and midres sets.
Note: This is a cherry-pick of these two VP9 changes:
https://chromium-review.googlesource.com/c/webm/libvpx/+/1108202
and
https://chromium-review.googlesource.com/c/webm/libvpx/+/1203975
But also some other changes:
- Correctly handle condition to break from loop for FIXED_GF_LENGTH.
- Change condition for using alt-ref frame.
- Allow q = 0 (lossless) preventing quality loss for some non-static
clips at high bitrates.
- No max capping for kf_boost, but use a minimum for static content.
STATS_CHANGED for very static videos
BUG=b/119104564
Change-Id: Ia4e7f7c1d7d5aa3a2b5962b6e1c5d5067bacc2d9
diff --git a/av1/encoder/firstpass.c b/av1/encoder/firstpass.c
index cd6b5e3..56fc611 100644
--- a/av1/encoder/firstpass.c
+++ b/av1/encoder/firstpass.c
@@ -58,7 +58,8 @@
#define KF_MAX_FRAME_BOOST 128.0
#define MIN_ARF_GF_BOOST 240
#define MIN_DECAY_FACTOR 0.01
-#define MIN_KF_BOOST 300
+#define MIN_KF_BOOST 300 // Minimum boost for non-static KF interval
+#define MIN_STATIC_KF_BOOST 5400 // Minimum boost for static KF interval
#define NEW_MV_MODE_PENALTY 32
#define DARK_THRESH 64
#define DEFAULT_GRP_WEIGHT 1.0
@@ -2019,7 +2020,10 @@
accumulative_subgroup_interval += subgroup_interval[cpi->num_extra_arfs];
}
- for (i = 0; i < rc->baseline_gf_interval - rc->source_alt_ref_pending; ++i) {
+ const int normal_frames =
+ rc->baseline_gf_interval - (key_frame || rc->source_alt_ref_pending);
+
+ for (i = 0; i < normal_frames; ++i) {
gf_group->arf_update_idx[frame_index] = which_arf;
gf_group->arf_ref_idx[frame_index] = which_arf;
@@ -2204,7 +2208,10 @@
#endif // USE_SYMM_MULTI_LAYER
// Allocate bits to the other frames in the group.
- for (i = 0; i < rc->baseline_gf_interval - rc->source_alt_ref_pending; ++i) {
+ const int normal_frames =
+ rc->baseline_gf_interval - (key_frame || rc->source_alt_ref_pending);
+
+ for (i = 0; i < normal_frames; ++i) {
FIRSTPASS_STATS frame_stats;
if (EOF == input_stats(twopass, &frame_stats)) break;
@@ -2275,8 +2282,7 @@
frame_index = tmp_frame_index;
// Re-distribute this extra budget to overlay frames in the group.
- for (i = 0; i < rc->baseline_gf_interval - rc->source_alt_ref_pending;
- ++i) {
+ for (i = 0; i < normal_frames; ++i) {
if (cpi->new_bwdref_update_rule &&
gf_group->update_type[frame_index] == INTNL_OVERLAY_UPDATE) {
assert(gf_group->pyramid_height <= MAX_PYRAMID_LVL &&
@@ -2334,6 +2340,12 @@
}
}
+// Returns true if KF group and GF group both are almost completely static.
+static INLINE int is_almost_static(double gf_zero_motion, int kf_zero_motion) {
+ return (gf_zero_motion >= 0.995) &&
+ (kf_zero_motion >= STATIC_KF_GROUP_THRESH);
+}
+
// Analyse and define a gf/arf group.
static void define_gf_group(AV1_COMP *cpi, FIRSTPASS_STATS *this_frame) {
AV1_COMMON *const cm = &cpi->common;
@@ -2481,8 +2493,10 @@
decay_accumulator = decay_accumulator * loop_decay_rate;
// Monitor for static sections.
- zero_motion_accumulator = AOMMIN(
- zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));
+ if ((rc->frames_since_key + i - 1) > 1) {
+ zero_motion_accumulator = AOMMIN(
+ zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));
+ }
// Break clause to detect very still sections after motion. For example,
// a static image after a fade or other transition.
@@ -2498,14 +2512,27 @@
decay_accumulator *
calc_frame_boost(cpi, &next_frame, this_frame_mv_in_out, GF_MAX_BOOST);
#if CONFIG_FIX_GF_LENGTH
- if (i == (FIXED_GF_LENGTH + 1)) break;
+ // If almost totally static, we will not use the FIXED_GF_LENGTH later, so
+ // we can continue for more frames.
+ if (i >= (FIXED_GF_LENGTH + 1) &&
+ !is_almost_static(zero_motion_accumulator,
+ twopass->kf_zeromotion_pct)) {
+ break;
+ }
#else
- // Skip breaking condition for CONFIG_FIX_GF_LENGTH
// Break out conditions.
- if (
- // Break at active_max_gf_interval unless almost totally static.
- (i >= (active_max_gf_interval + arf_active_or_kf) &&
- zero_motion_accumulator < 0.995) ||
+ // Break at maximum of active_max_gf_interval unless almost totally static.
+ //
+ // Note that the addition of a test of rc->source_alt_ref_active is
+ // deliberate. The effect of this is that after a normal altref group even
+ // if the material is static there will be one normal length GF group
+ // before allowing longer GF groups. The reason for this is that in cases
+ // such as slide shows where slides are separated by a complex transition
+ // such as a fade, the arf group spanning the transition may not be coded
+ // at a very high quality and hence this frame (with its overlay) is a
+ // poor golden frame to use for an extended group.
+ if ((i >= (active_max_gf_interval + arf_active_or_kf) &&
+ ((zero_motion_accumulator < 0.995) || (rc->source_alt_ref_active))) ||
(
// Don't break out with a very short interval.
(i >= active_min_gf_interval + arf_active_or_kf) &&
@@ -2551,23 +2578,24 @@
if (disable_bwd_extarf) cpi->extra_arf_allowed = 0;
+ const int use_alt_ref =
+ !is_almost_static(zero_motion_accumulator, twopass->kf_zeromotion_pct) &&
+ allow_alt_ref && (i < cpi->oxcf.lag_in_frames) &&
+ (i >= rc->min_gf_interval);
+
#define REDUCE_GF_LENGTH_THRESH 4
#define REDUCE_GF_LENGTH_TO_KEY_THRESH 9
#define REDUCE_GF_LENGTH_BY 1
int alt_offset = 0;
#if REDUCE_LAST_GF_LENGTH
- // TODO(weitinglin): The length reduction stretagy is tweaking using AOM_Q
- // mode, and hurting the performance of VBR mode. We need to investigate how
- // to adjust GF length for other modes.
+ // The length reduction strategy is tweaked using AOM_Q mode, and doesn't work
+ // for VBR mode.
+ // Also, we don't have do adjustment for lossless mode.
+ const int allow_gf_length_reduction =
+ (cpi->oxcf.rc_mode == AOM_Q || cpi->extra_arf_allowed == 0) &&
+ !is_lossless_requested(&cpi->oxcf);
- int allow_gf_length_reduction =
- cpi->oxcf.rc_mode == AOM_Q || cpi->extra_arf_allowed == 0;
-
- // We are going to have an alt ref, but we don't have do adjustment for
- // lossless mode
- if (allow_alt_ref && allow_gf_length_reduction &&
- (i < cpi->oxcf.lag_in_frames) && (i >= rc->min_gf_interval) &&
- !is_lossless_requested(&cpi->oxcf)) {
+ if (allow_gf_length_reduction && use_alt_ref) {
// adjust length of this gf group if one of the following condition met
// 1: only one overlay frame left and this gf is too long
// 2: next gf group is too short to have arf compared to the current gf
@@ -2591,11 +2619,10 @@
i -= roll_back;
}
}
-#endif
+#endif // REDUCE_LAST_GF_LENGTH
// Should we use the alternate reference frame.
- if (allow_alt_ref && (i < cpi->oxcf.lag_in_frames) &&
- (i >= rc->min_gf_interval)) {
+ if (use_alt_ref) {
// Calculate the boost for alt ref.
rc->gfu_boost =
calc_arf_boost(cpi, alt_offset, (i - 1), (i - 1), &f_boost, &b_boost);
@@ -2629,11 +2656,10 @@
rc->baseline_gf_interval = rc->frames_to_key - MIN_FWD_KF_INTERVAL;
}
} else {
- rc->baseline_gf_interval =
- i - (is_key_frame || rc->source_alt_ref_pending);
+ rc->baseline_gf_interval = i - rc->source_alt_ref_pending;
}
} else {
- rc->baseline_gf_interval = i - (is_key_frame || rc->source_alt_ref_pending);
+ rc->baseline_gf_interval = i - rc->source_alt_ref_pending;
}
#if REDUCE_LAST_ALT_BOOST
@@ -2883,6 +2909,7 @@
av1_zero(next_frame);
cpi->common.frame_type = KEY_FRAME;
+ rc->frames_since_key = 0;
// Reset the GF group data structures.
av1_zero(*gf_group);
@@ -3027,8 +3054,13 @@
if (EOF == input_stats(twopass, &next_frame)) break;
// Monitor for static sections.
- zero_motion_accumulator = AOMMIN(zero_motion_accumulator,
- get_zero_motion_factor(cpi, &next_frame));
+ // For the first frame in kf group, the second ref indicator is invalid.
+ if (i > 0) {
+ zero_motion_accumulator = AOMMIN(
+ zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));
+ } else {
+ zero_motion_accumulator = next_frame.pcnt_inter - next_frame.pcnt_motion;
+ }
// Not all frames in the group are necessarily used in calculating boost.
if ((i <= rc->max_gf_interval) ||
@@ -3060,10 +3092,18 @@
twopass->section_intra_rating = calculate_section_intra_ratio(
start_position, twopass->stats_in_end, rc->frames_to_key);
- // Apply various clamps for min and max boost
rc->kf_boost = (int)(av_decay_accumulator * boost_score);
- rc->kf_boost = AOMMAX(rc->kf_boost, (rc->frames_to_key * 3));
- rc->kf_boost = AOMMAX(rc->kf_boost, MIN_KF_BOOST);
+
+ // Special case for static / slide show content but don't apply
+ // if the kf group is very short.
+ if ((zero_motion_accumulator > STATIC_KF_GROUP_FLOAT_THRESH) &&
+ (rc->frames_to_key > 8)) {
+ rc->kf_boost = AOMMAX(rc->kf_boost, MIN_STATIC_KF_BOOST);
+ } else {
+ // Apply various clamps for min and max boost
+ rc->kf_boost = AOMMAX(rc->kf_boost, (rc->frames_to_key * 3));
+ rc->kf_boost = AOMMAX(rc->kf_boost, MIN_KF_BOOST);
+ }
// Work out how many bits to allocate for the key frame itself.
kf_bits = calculate_boost_bits((rc->frames_to_key - 1), rc->kf_boost,
diff --git a/av1/encoder/firstpass.h b/av1/encoder/firstpass.h
index 4b7325a..7c40615 100644
--- a/av1/encoder/firstpass.h
+++ b/av1/encoder/firstpass.h
@@ -109,23 +109,23 @@
typedef struct {
unsigned char index;
- RATE_FACTOR_LEVEL rf_level[(MAX_LAG_BUFFERS * 2) + 1];
- FRAME_UPDATE_TYPE update_type[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char arf_src_offset[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char arf_update_idx[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char arf_ref_idx[(MAX_LAG_BUFFERS * 2) + 1];
+ RATE_FACTOR_LEVEL rf_level[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ FRAME_UPDATE_TYPE update_type[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char arf_src_offset[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char arf_update_idx[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char arf_ref_idx[MAX_STATIC_GF_GROUP_LENGTH + 1];
#if USE_SYMM_MULTI_LAYER
- unsigned char arf_pos_in_gf[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char pyramid_level[(MAX_LAG_BUFFERS * 2) + 1];
+ unsigned char arf_pos_in_gf[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char pyramid_level[MAX_STATIC_GF_GROUP_LENGTH + 1];
unsigned char pyramid_height;
unsigned char pyramid_lvl_nodes[MAX_PYRAMID_LVL];
-#endif
- unsigned char brf_src_offset[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char bidir_pred_enabled[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char ref_fb_idx_map[(MAX_LAG_BUFFERS * 2) + 1][REF_FRAMES];
- unsigned char refresh_idx[(MAX_LAG_BUFFERS * 2) + 1];
- unsigned char refresh_flag[(MAX_LAG_BUFFERS * 2) + 1];
- int bit_allocation[(MAX_LAG_BUFFERS * 2) + 1];
+#endif // USE_SYMM_MULTI_LAYER
+ unsigned char brf_src_offset[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char bidir_pred_enabled[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char ref_fb_idx_map[MAX_STATIC_GF_GROUP_LENGTH + 1][REF_FRAMES];
+ unsigned char refresh_idx[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ unsigned char refresh_flag[MAX_STATIC_GF_GROUP_LENGTH + 1];
+ int bit_allocation[MAX_STATIC_GF_GROUP_LENGTH + 1];
} GF_GROUP;
typedef struct {
diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index f174c83..53c5ec7 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -991,6 +991,10 @@
active_best_quality =
get_kf_active_quality(rc, active_worst_quality, bit_depth);
+ if (cpi->twopass.kf_zeromotion_pct >= STATIC_KF_GROUP_THRESH) {
+ active_best_quality /= 4;
+ }
+
// Allow somewhat lower kf minq with small image formats.
if ((width * height) <= (352 * 288)) {
q_adj_factor -= 0.25;
@@ -1830,13 +1834,8 @@
rc->max_gf_interval = av1_rc_get_default_max_gf_interval(
cpi->framerate, rc->min_gf_interval);
- // Extended interval for genuinely static scenes
- rc->static_scene_max_gf_interval = MAX_LAG_BUFFERS * 2;
-
- if (is_altref_enabled(cpi)) {
- if (rc->static_scene_max_gf_interval > oxcf->lag_in_frames - 1)
- rc->static_scene_max_gf_interval = oxcf->lag_in_frames - 1;
- }
+ // Extended max interval for genuinely static scenes like slide shows.
+ rc->static_scene_max_gf_interval = MAX_STATIC_GF_GROUP_LENGTH;
if (rc->max_gf_interval > rc->static_scene_max_gf_interval)
rc->max_gf_interval = rc->static_scene_max_gf_interval;
diff --git a/av1/encoder/ratectrl.h b/av1/encoder/ratectrl.h
index 257cc88..4fe2d1c 100644
--- a/av1/encoder/ratectrl.h
+++ b/av1/encoder/ratectrl.h
@@ -24,6 +24,15 @@
// Bits Per MB at different Q (Multiplied by 512)
#define BPER_MB_NORMBITS 9
+// Threshold used to define if a KF group is static (e.g. a slide show).
+// Essentially, this means that no frame in the group has more than 1% of MBs
+// that are not marked as coded with 0,0 motion in the first pass.
+#define STATIC_KF_GROUP_THRESH 99
+#define STATIC_KF_GROUP_FLOAT_THRESH 0.99
+
+// The maximum duration of a GF group that is static (e.g. a slide show).
+#define MAX_STATIC_GF_GROUP_LENGTH 250
+
#define CUSTOMIZED_GF 1
#if CONFIG_FIX_GF_LENGTH
