From 984e7cb4e01ce423b3d989599fba08a98f3b36a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arttu=20Yl=C3=A4-Outinen?= <arttu.yla-outinen@tut.fi>
Date: Fri, 29 May 2015 14:00:51 +0300
Subject: [PATCH] Fix setting QP when rate control is disabled.

When rate control is disabled, QP and lambda are now selected like they
were before rate control was implemented.
---
 src/config.c       | 16 ++++++++--------
 src/config.h       |  2 ++
 src/encoderstate.c | 22 ++++++++++++++++------
 src/rate_control.c | 41 +++++++++++++++++++++++++++++++++++------
 src/rate_control.h |  2 ++
 5 files changed, 63 insertions(+), 20 deletions(-)

diff --git a/src/config.c b/src/config.c
index ea51b871..d1c0236f 100644
--- a/src/config.c
+++ b/src/config.c
@@ -537,35 +537,35 @@ static int config_parse(config_t *cfg, const char *name, const char *value)
     if(atoi(value) == 8) {
       // GOP
       cfg->gop_len = 8;
-      cfg->gop[0].poc_offset = 8; cfg->gop[0].layer = 1; cfg->gop[0].is_ref = 1;
+      cfg->gop[0].poc_offset = 8; cfg->gop[0].qp_offset = 1; cfg->gop[0].layer = 1; cfg->gop[0].qp_factor = 0.442;  cfg->gop[0].is_ref = 1;
       cfg->gop[0].ref_pos_count = 0;
       cfg->gop[0].ref_neg_count = 3; cfg->gop[0].ref_neg[0] = 8; cfg->gop[0].ref_neg[1] = 12; cfg->gop[0].ref_neg[2] = 16;
 
-      cfg->gop[1].poc_offset = 4; cfg->gop[1].layer = 2; cfg->gop[1].is_ref = 1;
+      cfg->gop[1].poc_offset = 4; cfg->gop[1].qp_offset = 2; cfg->gop[1].layer = 2; cfg->gop[1].qp_factor = 0.3536; cfg->gop[1].is_ref = 1;
       cfg->gop[1].ref_neg_count = 2; cfg->gop[1].ref_neg[0] = 4; cfg->gop[1].ref_neg[1] = 8;
       cfg->gop[1].ref_pos_count = 1; cfg->gop[1].ref_pos[0] = 4;
 
-      cfg->gop[2].poc_offset = 2; cfg->gop[2].layer = 3; cfg->gop[2].is_ref = 1;
+      cfg->gop[2].poc_offset = 2; cfg->gop[2].qp_offset = 3; cfg->gop[2].layer = 3; cfg->gop[2].qp_factor = 0.3536; cfg->gop[2].is_ref = 1;
       cfg->gop[2].ref_neg_count = 2; cfg->gop[2].ref_neg[0] = 2; cfg->gop[2].ref_neg[1] = 6;
       cfg->gop[2].ref_pos_count = 2; cfg->gop[2].ref_pos[0] = 2; cfg->gop[2].ref_pos[1] = 6;
 
-      cfg->gop[3].poc_offset = 1; cfg->gop[3].layer = 4; cfg->gop[3].is_ref = 0;
+      cfg->gop[3].poc_offset = 1; cfg->gop[3].qp_offset = 4; cfg->gop[3].layer = 4; cfg->gop[3].qp_factor = 0.68;   cfg->gop[3].is_ref = 0;
       cfg->gop[3].ref_neg_count = 1; cfg->gop[3].ref_neg[0] = 1;
       cfg->gop[3].ref_pos_count = 3; cfg->gop[3].ref_pos[0] = 1; cfg->gop[3].ref_pos[1] = 3; cfg->gop[3].ref_pos[2] = 7;
 
-      cfg->gop[4].poc_offset = 3; cfg->gop[4].layer = 4; cfg->gop[4].is_ref = 0;
+      cfg->gop[4].poc_offset = 3; cfg->gop[4].qp_offset = 4; cfg->gop[4].layer = 4; cfg->gop[4].qp_factor = 0.68;   cfg->gop[4].is_ref = 0;
       cfg->gop[4].ref_neg_count = 2; cfg->gop[4].ref_neg[0] = 1; cfg->gop[4].ref_neg[1] = 3;
       cfg->gop[4].ref_pos_count = 2; cfg->gop[4].ref_pos[0] = 1; cfg->gop[4].ref_pos[1] = 5;
 
-      cfg->gop[5].poc_offset = 6; cfg->gop[5].layer = 3; cfg->gop[5].is_ref = 1;
+      cfg->gop[5].poc_offset = 6; cfg->gop[5].qp_offset = 3; cfg->gop[5].layer = 3; cfg->gop[5].qp_factor = 0.3536; cfg->gop[5].is_ref = 1;
       cfg->gop[5].ref_neg_count = 2; cfg->gop[5].ref_neg[0] = 2; cfg->gop[5].ref_neg[1] = 6;
       cfg->gop[5].ref_pos_count = 1; cfg->gop[5].ref_pos[0] = 2;
 
-      cfg->gop[6].poc_offset = 5; cfg->gop[6].layer = 4;   cfg->gop[6].is_ref = 0;
+      cfg->gop[6].poc_offset = 5; cfg->gop[6].qp_offset = 4; cfg->gop[6].layer = 4; cfg->gop[6].qp_factor = 0.68;   cfg->gop[6].is_ref = 0;
       cfg->gop[6].ref_neg_count = 2;  cfg->gop[6].ref_neg[0] = 1; cfg->gop[6].ref_neg[1] = 5;
       cfg->gop[6].ref_pos_count = 2; cfg->gop[6].ref_pos[0] = 1; cfg->gop[6].ref_pos[1] = 3;
 
-      cfg->gop[7].poc_offset = 7; cfg->gop[7].layer = 4;   cfg->gop[7].is_ref = 0;
+      cfg->gop[7].poc_offset = 7; cfg->gop[7].qp_offset = 4; cfg->gop[7].layer = 4; cfg->gop[7].qp_factor = 0.68;   cfg->gop[7].is_ref = 0;
       cfg->gop[7].ref_neg_count = 3; cfg->gop[7].ref_neg[0] = 1; cfg->gop[7].ref_neg[1] = 3; cfg->gop[7].ref_neg[2] = 7;
       cfg->gop[7].ref_pos_count = 1; cfg->gop[7].ref_pos[0] = 1;
     } else if(atoi(value)) {
diff --git a/src/config.h b/src/config.h
index 20b64741..65da7243 100644
--- a/src/config.h
+++ b/src/config.h
@@ -29,6 +29,8 @@
 
 
 typedef struct {
+  double qp_factor;
+  int8_t qp_offset;    /*!< \brief QP offset */
   int8_t poc_offset;   /*!< \brief POC offset */
   int8_t layer;        /*!< \brief Current layer */
   int8_t is_ref;       /*!< \brief Flag if this picture is used as a reference */
diff --git a/src/encoderstate.c b/src/encoderstate.c
index 5d70c30e..a90e987e 100644
--- a/src/encoderstate.c
+++ b/src/encoderstate.c
@@ -45,10 +45,6 @@
 #include "rdo.h"
 #include "rate_control.h"
 
-#ifndef LMBD
-# define LMBD 1.0
-#endif
-
 int encoder_state_match_children_of_previous_frame(encoder_state_t * const state) {
   int i;
   for (i = 0; state->children[i].encoder_control; ++i) {
@@ -771,10 +767,24 @@ static void encoder_state_new_frame(encoder_state_t * const state) {
       encoder_state_ref_sort(state);
     }
 
-    double lambda = select_picture_lambda(state);
+    double lambda;
+    if (encoder->cfg->target_bitrate > 0) {
+      // Rate control enabled.
+      lambda = select_picture_lambda(state);
+      state->global->QP = lambda_to_QP(lambda);
+    } else {
+      if (encoder->cfg->gop_len > 0 && state->global->slicetype != SLICE_I) {
+        gop_config_t const * const gop =
+          encoder->cfg->gop + state->global->gop_offset;
+        state->global->QP = encoder->cfg->qp + gop->qp_offset;
+        state->global->QP_factor = gop->qp_factor;
+      } else {
+        state->global->QP = encoder->cfg->qp;
+      }
+      lambda = select_picture_lambda_from_qp(state);
+    }
     state->global->cur_lambda_cost = lambda;
     state->global->cur_lambda_cost_sqrt = sqrt(lambda);
-    state->global->QP = lambda_to_QP(lambda);
 
   } else {
     //Clear the bitstream if it's not the main encoder
diff --git a/src/rate_control.c b/src/rate_control.c
index fc7cb5f4..5b267499 100644
--- a/src/rate_control.c
+++ b/src/rate_control.c
@@ -108,22 +108,23 @@ static double pic_allocate_bits(const encoder_state_t * const state)
  * \brief Select a lambda value for encoding the next picture
  * \param state the main encoder state
  * \return lambda for the next picture
+ *
+ * Rate control must be enabled (i.e. cfg->target_bitrate > 0) when this
+ * function is called.
  */
 double select_picture_lambda(encoder_state_t * const state)
 {
   const encoder_control_t * const encoder = state->encoder_control;
 
-  if (encoder->cfg->target_bitrate <= 0) {
-    // Rate control disabled.
-    return exp((encoder->cfg->qp - 13.7223 - 0.5) / 4.2005);
-  }
+  assert(encoder->cfg->target_bitrate > 0);
 
   if (state->global->frame > encoder->cfg->owf) {
+    // At least one frame has been written.
     update_rc_parameters(state);
   }
 
   if (encoder->cfg->gop_len == 0 || state->global->gop_offset == 0) {
-    // a new GOP begins at this frame
+    // A new GOP begins at this frame.
     gop_allocate_bits(state);
   } else {
     state->global->cur_gop_target_bits =
@@ -141,6 +142,34 @@ double select_picture_lambda(encoder_state_t * const state)
 
 int8_t lambda_to_QP(const double lambda)
 {
-  int8_t qp = 4.2005 * log(lambda) + 13.7223 + 0.5;
+  const int8_t qp = 4.2005 * log(lambda) + 13.7223 + 0.5;
   return CLIP(0, 51, qp);
 }
+
+/**
+ * \brief Select a lambda value according to current QP value
+ * \param state the main encoder state
+ * \return lambda for the next picture
+ *
+ * This function should be used to select lambda when rate control is
+ * disabled.
+ */
+double select_picture_lambda_from_qp(encoder_state_t const * const state)
+{
+  const int gop_len = state->encoder_control->cfg->gop_len;
+  const double qp_temp = state->global->QP - 12;
+
+  double qp_factor;
+  if (state->global->slicetype == SLICE_I) {
+    const double lambda_scale = 1.0 - CLIP(0.0, 0.5, 0.05 * gop_len);
+    qp_factor = 0.57 * lambda_scale;
+  } else if (gop_len > 0) {
+    qp_factor = 0.95 * state->global->QP_factor;
+  } else {
+    // default QP factor from HM config
+    qp_factor = 0.95 * 0.4624;
+  }
+
+  const double lambda = qp_factor * pow(2.0, qp_temp / 3.0);
+  return lambda;
+}
diff --git a/src/rate_control.h b/src/rate_control.h
index 45ab0791..073a838d 100644
--- a/src/rate_control.h
+++ b/src/rate_control.h
@@ -31,4 +31,6 @@ double select_picture_lambda(encoder_state_t * const state);
 
 int8_t lambda_to_QP(const double lambda);
 
+double select_picture_lambda_from_qp(encoder_state_t const * const state);
+
 #endif // RATE_CONTROL_H_