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Add extra altref option for hierarchical structure

This CL is to hook up the implemented hierarchical structure
construction as well as its corresponding bitrate allocation
functionality with the defining of a GF group.

Currently the hierarchical structure is off by default. Hence this CL
has no impact on coding performance.

Change-Id: I9e1ddfd877559e99072c23970f7fe103b64ed9ee

--- a/vp9/encoder/vp9_encoder.h

+++ b/vp9/encoder/vp9_encoder.h

@@ -758,9 +758,7 @@

   int num_extra_arfs;

   int arf_pos_in_gf[MAX_EXT_ARFS + 1];

   int arf_pos_for_ovrly[MAX_EXT_ARFS + 1];

-

   int extra_arf_allowed;

-  int bwd_ref_allowed;

   vpx_roi_map_t roi;

 } VP9_COMP;

--- a/vp9/encoder/vp9_firstpass.c

+++ b/vp9/encoder/vp9_firstpass.c

@@ -2135,7 +2135,7 @@

   // (3) The bi-predictive group interval is strictly smaller than the

   //     golden group interval.

   const int is_bipred_enabled =

-      cpi->bwd_ref_allowed && rc->source_alt_ref_pending &&

+      cpi->extra_arf_allowed && rc->source_alt_ref_pending &&

       rc->bipred_group_interval &&

       rc->bipred_group_interval <=

           (rc->baseline_gf_interval - rc->source_alt_ref_pending);

@@ -2523,6 +2523,8 @@

       target_frame_size -= last_frame_reduction;

     }

+    // TODO(zoeliu): Further check whether following is needed for

+    //               hierarchical GF group structure.

     if (rc->source_alt_ref_pending && cpi->multi_arf_enabled) {

       target_frame_size -= (target_frame_size >> 4);

     }

@@ -2539,8 +2541,8 @@

       gf_group->bit_allocation[frame_index] =

           target_frame_size - (target_frame_size >> 1);

     } else if (gf_group->update_type[frame_index] == BIPRED_UPDATE) {

-      // TODO(zoeliu): To investigate whether the allocated bits on

-      // BIPRED_UPDATE frames need to be further adjusted.

+      // TODO(zoeliu): Investigate whether the allocated bits on BIPRED_UPDATE

+      //               frames need to be further adjusted.

       gf_group->bit_allocation[frame_index] = target_frame_size;

     } else {

       assert(gf_group->update_type[frame_index] == LF_UPDATE ||

@@ -2753,6 +2755,8 @@

   const int is_key_frame = frame_is_intra_only(cm);

   const int arf_active_or_kf = is_key_frame || rc->source_alt_ref_active;

+  int disable_bwd_extarf;

+

   // Reset the GF group data structures unless this is a key

   // frame in which case it will already have been done.

   if (is_key_frame == 0) {

@@ -2933,6 +2937,39 @@

   rc->frames_till_gf_update_due = rc->baseline_gf_interval;

+  // TODO(zoeliu): Turn on the option to disable extra ALTREFs for still GF

+  //               groups.

+  // Disable extra altrefs for "still" gf group:

+  //   zero_motion_accumulator: minimum percentage of (0,0) motion;

+  //   avg_sr_coded_error:      average of the SSE per pixel of each frame;

+  //   avg_raw_err_stdev:       average of the standard deviation of (0,0)

+  //                            motion error per block of each frame.

+#if 0

+  assert(num_mbs > 0);

+  disable_bwd_extarf =

+      (zero_motion_accumulator > MIN_ZERO_MOTION &&

+       avg_sr_coded_error / num_mbs < MAX_SR_CODED_ERROR &&

+       avg_raw_err_stdev < MAX_RAW_ERR_VAR);

+#else

+  disable_bwd_extarf = 0;

+#endif  // 0

+

+  if (disable_bwd_extarf) cpi->extra_arf_allowed = 0;

+

+  if (!cpi->extra_arf_allowed) {

+    cpi->num_extra_arfs = 0;

+  } else {

+    // Compute how many extra alt_refs we can have

+    cpi->num_extra_arfs = get_number_of_extra_arfs(rc->baseline_gf_interval,

+                                                   rc->source_alt_ref_pending);

+  }

+  // Currently at maximum two extra ARFs' are allowed

+  assert(cpi->num_extra_arfs <= MAX_EXT_ARFS);

+

+  rc->bipred_group_interval = BFG_INTERVAL;

+  // The minimum bi-predictive frame group interval is 2.

+  if (rc->bipred_group_interval < 2) rc->bipred_group_interval = 0;

+

   // Reset the file position.

   reset_fpf_position(twopass, start_pos);

@@ -2984,13 +3021,7 @@

   twopass->kf_group_error_left -= gf_group_err;

   // Allocate bits to each of the frames in the GF group.

-  cpi->bwd_ref_allowed = 0;

-  cpi->extra_arf_allowed = 0;

-

-  cpi->num_extra_arfs = 0;

-  cpi->num_extra_arfs = cpi->extra_arf_allowed ? cpi->num_extra_arfs : 0;

-

-  if (cpi->bwd_ref_allowed) {

+  if (cpi->extra_arf_allowed) {

     allocate_gf_multi_arf_bits(cpi, gf_group_bits, gf_arf_bits);

   } else {

     allocate_gf_group_bits(cpi, gf_group_bits, gf_arf_bits);

--- a/vp9/encoder/vp9_firstpass.h

+++ b/vp9/encoder/vp9_firstpass.h

@@ -11,6 +11,8 @@

 #ifndef VP9_ENCODER_VP9_FIRSTPASS_H_

 #define VP9_ENCODER_VP9_FIRSTPASS_H_

+#include <assert.h>

+

 #include "vp9/encoder/vp9_lookahead.h"

 #include "vp9/encoder/vp9_ratectrl.h"

@@ -41,7 +43,12 @@

 #define INVALID_ROW -1

+// Length of the bi-predictive frame group (BFG)

+// NOTE: Currently each BFG contains one backward ref (BWF) frame plus a certain

+//       number of bi-predictive frames.

+#define BFG_INTERVAL 2

 #define MAX_EXT_ARFS 2

+#define MIN_EXT_ARF_INTERVAL 4

 typedef struct {

   double frame_mb_intra_factor;

@@ -209,6 +216,17 @@

 void calculate_coded_size(struct VP9_COMP *cpi, int *scaled_frame_width,

                           int *scaled_frame_height);

+

+static INLINE int get_number_of_extra_arfs(int interval, int arf_pending) {

+  assert(MAX_EXT_ARFS > 0);

+  if (arf_pending) {

+    if (interval >= MIN_EXT_ARF_INTERVAL * (MAX_EXT_ARFS + 1))

+      return MAX_EXT_ARFS;

+    else if (interval >= MIN_EXT_ARF_INTERVAL * MAX_EXT_ARFS)

+      return MAX_EXT_ARFS - 1;

+  }

+  return 0;

+}

 #ifdef __cplusplus

 }  // extern "C"