From: Paul Wilkins <paulwilkins@google.com>
Date: Tue, 15 Apr 2014 01:06:52 +0000 (-0700)
Subject: Add experimental VBR adaptation method.
X-Git-Tag: v1.4.0~1761^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=085f76e535a4376042d8eeadb1e4c5f246d74802;p=libvpx

Add experimental VBR adaptation method.

Add code to monitor over and under spend and
apply limited correction to the data rate of subsequent
frames. To prevent the problem of starvation or overspend
on individual frames (especially near the end of a clip) the
maximum adjustment on a single frame is limited to a %
of its un-modified allocation.

Change-Id: I6e1ca035ab8afb0c98eac4392115d0752d9cbd7f
---

diff --git a/vp9/encoder/vp9_firstpass.c b/vp9/encoder/vp9_firstpass.c
index 37f9cc679..210f43896 100644
--- a/vp9/encoder/vp9_firstpass.c
+++ b/vp9/encoder/vp9_firstpass.c
@@ -61,7 +61,7 @@
 #define MIN_GF_INTERVAL             4
 #endif
 
-#define DISABLE_RC_LONG_TERM_MEM
+#define LONG_TERM_VBR_CORRECTION
 
 static void swap_yv12(YV12_BUFFER_CONFIG *a, YV12_BUFFER_CONFIG *b) {
   YV12_BUFFER_CONFIG temp = *a;
@@ -1033,6 +1033,9 @@ void vp9_init_second_pass(VP9_COMP *cpi) {
 
     reset_fpf_position(twopass, start_pos);
   }
+
+  // Reset the vbr bits off target counter
+  cpi->rc.vbr_bits_off_target = 0;
 }
 
 // This function gives an estimate of how badly we believe the prediction
@@ -2192,6 +2195,23 @@ void vp9_rc_get_first_pass_params(VP9_COMP *cpi) {
   cpi->rc.frames_to_key = INT_MAX;
 }
 
+// For VBR...adjustment to the frame target based on error from previous frames
+void vbr_rate_correction(int * this_frame_target,
+                         const int64_t vbr_bits_off_target) {
+  int max_delta = *this_frame_target / 10;
+
+  // vbr_bits_off_target > 0 means we have extra bits to spend
+  if (vbr_bits_off_target > 0) {
+    *this_frame_target +=
+      (vbr_bits_off_target > max_delta) ? max_delta
+                                        : (int)vbr_bits_off_target;
+  } else {
+    *this_frame_target -=
+      (vbr_bits_off_target < -max_delta) ? max_delta
+                                         : (int)-vbr_bits_off_target;
+  }
+}
+
 void vp9_rc_get_second_pass_params(VP9_COMP *cpi) {
   VP9_COMMON *const cm = &cpi->common;
   RATE_CONTROL *const rc = &cpi->rc;
@@ -2219,8 +2239,15 @@ void vp9_rc_get_second_pass_params(VP9_COMP *cpi) {
     return;
 
   if (cpi->refresh_alt_ref_frame) {
+    int modified_target = twopass->gf_bits;
+    rc->base_frame_target = twopass->gf_bits;
     cm->frame_type = INTER_FRAME;
-    vp9_rc_set_frame_target(cpi, twopass->gf_bits);
+#ifdef LONG_TERM_VBR_CORRECTION
+    // Correction to rate target based on prior over or under shoot.
+    if (cpi->oxcf.end_usage == USAGE_LOCAL_FILE_PLAYBACK)
+      vbr_rate_correction(&modified_target, rc->vbr_bits_off_target);
+#endif
+    vp9_rc_set_frame_target(cpi, modified_target);
     return;
   }
 
@@ -2315,6 +2342,13 @@ void vp9_rc_get_second_pass_params(VP9_COMP *cpi) {
     target = vp9_rc_clamp_iframe_target_size(cpi, rc->this_frame_target);
   else
     target = vp9_rc_clamp_pframe_target_size(cpi, rc->this_frame_target);
+
+  rc->base_frame_target = target;
+#ifdef LONG_TERM_VBR_CORRECTION
+  // Correction to rate target based on prior over or under shoot.
+  if (cpi->oxcf.end_usage == USAGE_LOCAL_FILE_PLAYBACK)
+    vbr_rate_correction(&target, rc->vbr_bits_off_target);
+#endif
   vp9_rc_set_frame_target(cpi, target);
 
   // Update the total stats remaining structure.
@@ -2322,20 +2356,38 @@ void vp9_rc_get_second_pass_params(VP9_COMP *cpi) {
 }
 
 void vp9_twopass_postencode_update(VP9_COMP *cpi) {
-#ifdef DISABLE_RC_LONG_TERM_MEM
-  const uint64_t bits_used = cpi->rc.this_frame_target;
+  RATE_CONTROL *const rc = &cpi->rc;
+#ifdef LONG_TERM_VBR_CORRECTION
+  // In this experimental mode, the VBR correction is done exclusively through
+  // rc->vbr_bits_off_target. Based on the sign of this value, a limited %
+  // adjustment is made to the target rate of subsequent frames, to try and
+  // push it back towards 0. This mode is less likely to suffer from
+  // extreme behaviour at the end of a clip or group of frames.
+  const int bits_used = rc->base_frame_target;
+  rc->vbr_bits_off_target += rc->base_frame_target - rc->projected_frame_size;
 #else
-  const uint64_t bits_used = cpi->rc.projected_frame_size;
+  // In this mode, VBR correction is acheived by altering bits_left,
+  // kf_group_bits & gf_group_bits to reflect any deviation from the target
+  // rate in this frame. This alters the allocation of bits to the
+  // remaning frames in the group / clip.
+  // This method can give rise to unstable behaviour near the end of a clip
+  // or kf/gf group of frames where any accumulated error is corrected over an
+  // ever decreasing number of frames.
+  const int bits_used = rc->projected_frame_size;
 #endif
+
   cpi->twopass.bits_left -= bits_used;
   cpi->twopass.bits_left = MAX(cpi->twopass.bits_left, 0);
-  // Update bits left to the kf and gf groups to account for overshoot or
-  // undershoot on these frames.
+
+#ifdef LONG_TERM_VBR_CORRECTION
+  if (cpi->common.frame_type != KEY_FRAME) {
+#else
   if (cpi->common.frame_type == KEY_FRAME) {
     // For key frames kf_group_bits already had the target bits subtracted out.
     // So now update to the correct value based on the actual bits used.
     cpi->twopass.kf_group_bits += cpi->rc.this_frame_target - bits_used;
   } else {
+#endif
     cpi->twopass.kf_group_bits -= bits_used;
     cpi->twopass.gf_group_bits -= bits_used;
     cpi->twopass.gf_group_bits = MAX(cpi->twopass.gf_group_bits, 0);
diff --git a/vp9/encoder/vp9_onyx_if.c b/vp9/encoder/vp9_onyx_if.c
index c609a27e9..e9d714df2 100644
--- a/vp9/encoder/vp9_onyx_if.c
+++ b/vp9/encoder/vp9_onyx_if.c
@@ -1997,8 +1997,8 @@ static void output_frame_level_debug_stats(VP9_COMP *cpi) {
   recon_err = vp9_get_y_sse(cpi->Source, get_frame_new_buffer(cm));
 
   if (cpi->twopass.total_left_stats.coded_error != 0.0)
-    fprintf(f, "%10u %10d %10d %10d %10d %10d "
-        "%10"PRId64" %10"PRId64" %10d "
+    fprintf(f, "%10u %10d %10d %10d %10d"
+        "%10"PRId64" %10"PRId64" %10"PRId64" %10"PRId64" %10d "
         "%7.2lf %7.2lf %7.2lf %7.2lf %7.2lf"
         "%6d %6d %5d %5d %5d "
         "%10"PRId64" %10.3lf"
@@ -2007,6 +2007,7 @@ static void output_frame_level_debug_stats(VP9_COMP *cpi) {
         cpi->rc.projected_frame_size,
         cpi->rc.projected_frame_size / cpi->common.MBs,
         (cpi->rc.projected_frame_size - cpi->rc.this_frame_target),
+        cpi->rc.vbr_bits_off_target,
         cpi->rc.total_target_vs_actual,
         (cpi->oxcf.starting_buffer_level - cpi->rc.bits_off_target),
         cpi->rc.total_actual_bits, cm->base_qindex,
diff --git a/vp9/encoder/vp9_ratectrl.c b/vp9/encoder/vp9_ratectrl.c
index c073a034e..040655e14 100644
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -1043,6 +1043,7 @@ void vp9_rc_set_frame_target(VP9_COMP *cpi, int target) {
   RATE_CONTROL *const rc = &cpi->rc;
 
   rc->this_frame_target = target;
+
   // Target rate per SB64 (including partial SB64s.
   rc->sb64_target_rate = ((int64_t)rc->this_frame_target * 64 * 64) /
                              (cm->width * cm->height);
diff --git a/vp9/encoder/vp9_ratectrl.h b/vp9/encoder/vp9_ratectrl.h
index 036470001..0e79c0fc3 100644
--- a/vp9/encoder/vp9_ratectrl.h
+++ b/vp9/encoder/vp9_ratectrl.h
@@ -27,7 +27,9 @@ extern "C" {
 
 typedef struct {
   // Rate targetting variables
-  int this_frame_target;
+  int base_frame_target;           // A baseline frame target before adjustment
+                                   // for previous under or over shoot.
+  int this_frame_target;           // Actual frame target after rc adjustment.
   int projected_frame_size;
   int sb64_target_rate;
   int last_q[3];                   // Separate values for Intra/Inter/ARF-GF
@@ -67,6 +69,7 @@ typedef struct {
 
   int64_t buffer_level;
   int64_t bits_off_target;
+  int64_t vbr_bits_off_target;
 
   int decimation_factor;
   int decimation_count;