From 83430a49f293c24e1c6096d0b04ddd82d5d43d17 Mon Sep 17 00:00:00 2001
From: Marko Viitanen <fador@iki.fi>
Date: Wed, 24 Nov 2021 21:57:46 +0200
Subject: [PATCH] [tmvp] Round TMVP colocated MVs using float conversion from
 VTM

---
 src/inter.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/src/inter.c b/src/inter.c
index 24dac4e8..5768cfcf 100644
--- a/src/inter.c
+++ b/src/inter.c
@@ -38,6 +38,7 @@
 
 #include "encoder.h"
 #include "imagelist.h"
+#include "kvz_math.h"
 #include "strategies/generic/picture-generic.h"
 #include "strategies/strategies-ipol.h"
 #include "videoframe.h"
@@ -1098,6 +1099,47 @@ static INLINE int16_t get_scaled_mv(int16_t mv, int scale)
   return CLIP(-32768, 32767, (scaled + 127 + (scaled < 0)) >> 8);
 }
 
+#define MV_EXPONENT_BITCOUNT 4
+#define MV_MANTISSA_BITCOUNT 6
+#define MV_MANTISSA_UPPER_LIMIT ((1 << (MV_MANTISSA_BITCOUNT - 1)) - 1)
+#define MV_MANTISSA_LIMIT (1 << (MV_MANTISSA_BITCOUNT - 1))
+#define MV_EXPONENT_MASK ((1 << MV_EXPONENT_BITCOUNT) - 1)
+
+static int convert_mv_fixed_to_float(int32_t val)
+{
+  int sign = val >> 31;
+  int scale = kvz_math_floor_log2((val ^ sign) | MV_MANTISSA_UPPER_LIMIT) - (MV_MANTISSA_BITCOUNT - 1);
+
+  int exponent;
+  int mantissa;
+  if (scale >= 0)
+  {
+    int round = (1 << scale) >> 1;
+    int n = (val + round) >> scale;
+    exponent = scale + ((n ^ sign) >> (MV_MANTISSA_BITCOUNT - 1));
+    mantissa = (n & MV_MANTISSA_UPPER_LIMIT) | (sign << (MV_MANTISSA_BITCOUNT - 1));
+  }
+  else
+  {
+    exponent = 0;
+    mantissa = val;
+  }
+
+  return exponent | (mantissa << MV_EXPONENT_BITCOUNT);
+}
+
+static int convert_mv_float_to_fixed(int val)
+{
+  int exponent = val & MV_EXPONENT_MASK;
+  int mantissa = val >> MV_EXPONENT_BITCOUNT;
+  return exponent == 0 ? mantissa : (mantissa ^ MV_MANTISSA_LIMIT) << (exponent - 1);
+}
+
+static int round_mv_comp(int x)
+{
+  return convert_mv_float_to_fixed(convert_mv_fixed_to_float(x));
+}
+
 static void apply_mv_scaling_pocs(int32_t current_poc,
                                   int32_t current_ref_poc,
                                   int32_t neighbor_poc,
@@ -1187,6 +1229,10 @@ static bool add_temporal_candidate(const encoder_state_t *state,
 
   mv_out[0] = colocated->inter.mv[col_list][0];
   mv_out[1] = colocated->inter.mv[col_list][1];
+
+  mv_out[0] = round_mv_comp(mv_out[0]);
+  mv_out[1] = round_mv_comp(mv_out[1]);
+
   apply_mv_scaling_pocs(
     state->frame->poc,
     state->frame->ref->pocs[current_ref],