From 31fc8edb9ce38e779e3d9514cb59b402bef1e58b Mon Sep 17 00:00:00 2001
From: Ram Mohan M <ram.mohan@ittiam.com>
Date: Sat, 30 Sep 2023 01:46:15 +0530
Subject: [PATCH] libavcenc: Correct Lagrange parameter for I, P & B slices

The Lambda tables for intra and inter(P) slices are slightly
modified. Lambda tables for B slices is completely replaced
wih new set.

This change is done in accordance with JVT-O079.doc
---
 encoder/ih264e_globals.c | 22 +++++++++++++++++++++-
 encoder/ih264e_globals.h |  3 ++-
 encoder/ih264e_me.c      | 11 ++++++++---
 encoder/ih264e_process.c |  9 ++++++++-
 4 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/encoder/ih264e_globals.c b/encoder/ih264e_globals.c
index 2639273d..fdc6837c 100644
--- a/encoder/ih264e_globals.c
+++ b/encoder/ih264e_globals.c
@@ -62,7 +62,7 @@
 * (from rate distortion optimization for video compression by sullivan).
 ******************************************************************************
 */
-const UWORD16 gu2_qp_lambda[52]=
+const UWORD8 gu1_qp_lambdaIP[52]=
 {
        0,      0,      0,      0,      0,      0,      0,      1,
        1,      1,      1,      1,      1,      1,      1,      1,
@@ -73,6 +73,26 @@ const UWORD16 gu2_qp_lambda[52]=
       59,     66,     74,     83,
 };
 
+/**
+******************************************************************************
+* @brief  lambda for varying quantizer scales that would be used to
+* compute the RD cost while deciding on the MB modes.
+* input  : qp
+* output : lambda
+* @remarks lambda = max(2, min(4, pow(2, (qp - 12)/6))) * gu1_qp_lambdaIP[]
+******************************************************************************
+*/
+const UWORD8 gu1_qp_lambdaB[52]=
+{
+        0,       0,       0,       0,       1,       1,       1,       1,
+        1,       1,       1,       1,       1,       1,       2,       2,
+        2,       2,       3,       3,       3,       4,       4,       5,
+        5,       6,       7,       8,      10,      11,      13,      15,
+       17,      20,      22,      26,      30,      33,      37,      42,
+       47,      53,      59,      66,      74,      83,      94,     105,
+      118,     132,     149,     167,
+};
+
 /**
 ******************************************************************************
 * @brief  Lamda for varying quantizer scales that would be used to
diff --git a/encoder/ih264e_globals.h b/encoder/ih264e_globals.h
index 5ce1dc88..3c9ea1f7 100644
--- a/encoder/ih264e_globals.h
+++ b/encoder/ih264e_globals.h
@@ -43,7 +43,8 @@
 /* Global Declarations                                                       */
 /*****************************************************************************/
 
-extern const UWORD16 gu2_qp_lambda[52];
+extern const UWORD8 gu1_qp_lambdaIP[52];
+extern const UWORD8 gu1_qp_lambdaB[52];
 extern const UWORD8 gu1_qp0[52];
 extern const UWORD8 u1_uev_codelength[32];
 extern const UWORD8 gu1_coeff_cost[6];
diff --git a/encoder/ih264e_me.c b/encoder/ih264e_me.c
index f4822191..7b1d5f3e 100644
--- a/encoder/ih264e_me.c
+++ b/encoder/ih264e_me.c
@@ -825,9 +825,14 @@ void ih264e_init_me(process_ctxt_t *ps_proc)
     ps_me_ctxt->apu1_ref_buf_luma[0] = ps_proc->apu1_ref_buf_luma[0];
     ps_me_ctxt->apu1_ref_buf_luma[1] = ps_proc->apu1_ref_buf_luma[1];
 
-    ps_me_ctxt->u4_lambda_motion = gu1_qp0[ps_me_ctxt->u1_mb_qp];
-
-
+    if (ps_codec->pic_type == PIC_B)
+    {
+        ps_me_ctxt->u4_lambda_motion = gu1_qp_lambdaB[ps_me_ctxt->u1_mb_qp];
+    }
+    else
+    {
+        ps_me_ctxt->u4_lambda_motion = gu1_qp_lambdaIP[ps_me_ctxt->u1_mb_qp];
+    }
 }
 
 
diff --git a/encoder/ih264e_process.c b/encoder/ih264e_process.c
index d3212c06..5e55a143 100644
--- a/encoder/ih264e_process.c
+++ b/encoder/ih264e_process.c
@@ -1458,7 +1458,14 @@ IH264E_ERROR_T ih264e_init_proc_ctxt(process_ctxt_t *ps_proc)
     ps_proc->u4_mb_type = I16x16;
 
     /* lambda */
-    ps_proc->u4_lambda = gu1_qp0[ps_qp_params->u1_mb_qp];
+    if (ps_codec->pic_type == PIC_B)
+    {
+        ps_proc->u4_lambda = gu1_qp_lambdaB[ps_qp_params->u1_mb_qp];
+    }
+    else
+    {
+        ps_proc->u4_lambda = gu1_qp_lambdaIP[ps_qp_params->u1_mb_qp];
+    }
 
     /* mb distortion */
     ps_proc->i4_mb_distortion = SHRT_MAX;