Better lambda cost implementation (from HM12)

- Lambda array changed to double as in HM
 - Needs updating when GOP / B-pictures are used

src/debug.c

@@ -68,7 +68,7 @@ unsigned render_cu_file(encoder_control *encoder, picture *pic,
 {
   cu_info *cu = &pic->cu_array[depth][xCtb + yCtb * (pic->width_in_lcu<<MAX_DEPTH)];
   cu_info *final_cu = &pic->cu_array[MAX_DEPTH][xCtb + yCtb * (pic->width_in_lcu<<MAX_DEPTH)];
-  unsigned lambda_cost = (4 * g_lambda_cost[encoder->QP]) << 4;
+  unsigned lambda_cost = (4 * g_lambda_cost[encoder->QP]);
   unsigned sum = 0;
   unsigned best_cost = -1;
   char type = cu->type == CU_INTRA ? 'I' : 'P';

src/encoder.c

@@ -42,7 +42,7 @@
 #include "sao.h"
 #include "rdo.h"
 
-int16_t g_lambda_cost[55];
+double g_lambda_cost[55];
 uint32_t* g_sig_last_scan[3][7];
 
 /* Local functions. */
@@ -179,6 +179,7 @@ void init_tables(void)
 {
   int i;
   int c = 0;
+
   memset( g_convert_to_bit,-1, sizeof( g_convert_to_bit ) );  
 
   for (i = 4; i < (1 << 7); i *= 2) {
@@ -199,27 +200,35 @@ void init_tables(void)
     c <<= 1;
   }
 
-  // Lambda cost
-  // TODO: cleanup
-  for (i = 0; i < 55; i++) {
-
-    // Force minimum lambda cost of 1
-    if (i < 15) {
-      g_lambda_cost[i] = 1;
-    } else {
-      g_lambda_cost[i] = (int16_t)sqrt(0.57 * pow(2.0, (i - 12) / 3));
 }
 
-    /**
-     * While working on RDOQ it was clear that the current lambda cost is wrong (compared to HM)
-     * so the cost is now lambda*lambda to fix some of those issues.
-     * This is not the final solution and this should be fixed by calculating the lambda like HM.
-     * TODO: fix lambda cost calculation
-     * - Marko Viitanen (Fador)
-     **/
-    g_lambda_cost[i] = g_lambda_cost[i]*g_lambda_cost[i];
+/*!
+  \brief Initializes lambda-value for current QP
+ 
+  Implementation closer to HM (Used HM12 as reference)
+   - Still missing functionality when GOP and B-pictures are used 
+ */
+void init_lambda(encoder_control *encoder)
+{
+  double qp = encoder->QP;  
+  double lambda_scale = 1.0;
+  double qp_temp      = qp - 12;
+  double lambda;
+
+  // Default QP-factor from HM config
+  double qp_factor = 0.4624;
+
+  if (encoder->in.cur_pic->slicetype == SLICE_I) {
+    qp_factor=0.57*lambda_scale;
   }
 
+  lambda = qp_factor*pow( 2.0, qp_temp/3.0 );
+
+  if (encoder->in.cur_pic->slicetype != SLICE_I ) {
+    lambda *= 0.95;
+  }
+  
+  g_lambda_cost[encoder->QP] = lambda;
 }
 
 void free_tables(void)
@@ -362,6 +371,9 @@ void init_encoder_input(encoder_input *input, FILE *inputfile,
 void encode_one_frame(encoder_control* encoder)
 {
 
+  // Initialize lambda value(s) to use in search
+  init_lambda(encoder);
+
   /** IDR picture when: period == 0 and frame == 0
    *                    period == 1 && frame%2 == 0
    *                    period != 0 && frame%period == 0   

src/encoder.h

@@ -81,6 +81,7 @@ typedef struct
 } encoder_control;
 
 void init_tables(void);
+void init_lambda(encoder_control* encoder);
 void free_tables(void);
 encoder_control *init_encoder_control(config *cfg);
 void init_encoder_input(encoder_input *input, FILE* inputfile,
@@ -107,7 +108,7 @@ void encode_transform_coeff(encoder_control *encoder, int32_t x_cu, int32_t y_cu
 void encode_block_residual(encoder_control *encoder, 
                            uint16_t x_ctb, uint16_t y_ctb, uint8_t depth);
 
-extern int16_t g_lambda_cost[55];
+extern double g_lambda_cost[55];
 extern uint32_t* g_sig_last_scan[3][7];
 int8_t g_convert_to_bit[LCU_WIDTH + 1];
 static int8_t g_bitdepth     = 8;

src/search.c

@@ -336,7 +336,7 @@ void search_intra(encoder_control *encoder, uint16_t x_ctb, uint16_t y_ctb, uint
     int nn_cost = cur_cu->intra[0].cost;
     int nn_mode = cur_cu->intra[0].mode;
     int i;
-    int cost = g_lambda_cost[encoder->QP] << 8;
+    int cost = g_lambda_cost[encoder->QP] * 256.0;
     static vector2d offsets[4] = {{0,0},{1,0},{0,1},{1,1}};
     width = 4;
     recShift = &rec[width * 2 + 8 + 1];