Cabac optimizations

Optimized cabac functions for writing bypass bins.
Removed unused return from cabac flush function.
Removed the macro REV_NBITS.

Bug: 22860270

Change-Id: Iece82797f2f45a35281817a2b77a7c7fe4e02bd1

3 files changed, 32 insertions, 75 deletions

diff --git a/encoder/ih264e_cabac.c b/encoder/ih264e_cabac.c
index 64ff7cd..26ded4d 100644
--- a/encoder/ih264e_cabac.c
+++ b/encoder/ih264e_cabac.c
@@ -111,29 +111,28 @@
  *
  *******************************************************************************
  */
+
 UWORD32 ih264e_cabac_UEGk0_binarization(WORD16 i2_sufs, WORD8 *pi1_bins_len)
 {
-    UWORD32 u4_bins;
-    WORD32 i4_len;
-    WORD16 x, y;
-
-    x = i2_sufs + 1;
-    i4_len = CLZ(x);
-    i4_len = 31 - i4_len;
-    y = 1 << i4_len;
-    y = y - 1;
-    i2_sufs = i2_sufs - y;
-    u4_bins = y << 1;
-    u4_bins = u4_bins << i4_len;
-    u4_bins = u4_bins + i2_sufs;
-
-    REV(u4_bins, u4_bins);
-    u4_bins = u4_bins >> (31 - 2 * i4_len);
-    (*pi1_bins_len) = 2 * i4_len + 1;
-
-    return (u4_bins);
-}
+    WORD32 unary_length;
+    UWORD32 u4_sufs_shiftk_plus1, u4_egk, u4_unary_bins;
+
+    u4_sufs_shiftk_plus1 = i2_sufs + 1;
+
+    unary_length = (32 - CLZ(u4_sufs_shiftk_plus1) + (0 == u4_sufs_shiftk_plus1));
+
+    /* unary code with (unary_length-1) '1's and terminating '0' bin */
+    u4_unary_bins = (1 << unary_length) - 2;
+
+    /* insert the symbol prefix of (unary length - 1)  bins */
+    u4_egk = (u4_unary_bins << (unary_length - 1))
+                    | (u4_sufs_shiftk_plus1 & ((1 << (unary_length - 1)) - 1));
 
+    /* length of the code = 2 *(unary_length - 1) + 1 + k */
+    *pi1_bins_len = (2 * unary_length) - 1;
+
+    return (u4_egk);
+}
 
 /**
  *******************************************************************************
@@ -236,14 +235,14 @@ void ih264e_get_cabac_context(entropy_ctxt_t *ps_ent_ctxt, WORD32 u4_mb_type)
  *  @param[in]   ps_cabac_ctxt
  *  pointer to cabac context (handle)
  *
- * @returns  success or failure error code
+ * @returns  none
  *
  * @remarks
  *  None
  *
  *******************************************************************************
  */
-WORD32 ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt)
+void ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt)
 {
 
     /* bit stream ptr */
@@ -267,17 +266,6 @@ WORD32 ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt)
         WORD32 bits_left;
         WORD32 rem_bits;
 
-        /*********************************************************************/
-        /* Bitstream overflow check                                          */
-        /* NOTE: corner case of epb bytes (max 2 for 32bit word) not handled */
-        /*********************************************************************/
-        if ((u4_strm_buf_offset + u4_out_standing_bytes + 1)
-                        >= ps_stream->u4_max_strm_size)
-        {
-            /* return without corrupting the buffer beyond its size */
-            return (IH264E_BITSTREAM_BUFFER_OVERFLOW);
-        }
-
         if (carry)
         {
             /* CORNER CASE: if the previous data is 0x000003, then EPB will be inserted
@@ -336,7 +324,6 @@ WORD32 ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt)
         ps_stream->u4_cur_word = 0;
         ps_stream->i4_bits_left_in_cw = WORD_SIZE;
 
-        return (IH264E_SUCCESS);
     }
 }
 
@@ -763,7 +750,6 @@ void ih264e_cabac_encode_bypass_bins(cabac_ctxt_t *ps_cabac, UWORD32 u4_bins,
 
     UWORD32 u4_range = ps_cab_enc_env->u4_code_int_range;
     WORD32 next_byte;
-    UWORD32 rev_next_byte;
 
     /* Sanity checks */
     ASSERT((num_bins < 33) && (num_bins > 0));
@@ -777,14 +763,11 @@ void ih264e_cabac_encode_bypass_bins(cabac_ctxt_t *ps_cabac, UWORD32 u4_bins,
     {
         num_bins -= 8;
 
-        /* extract the leading 8 bins */
-        next_byte = (u4_bins) & 0xff;
-        u4_bins >>= 8;
-        REV_NBITS(next_byte, 8, rev_next_byte);
+        next_byte = (u4_bins >> (num_bins)) & 0xff;
 
         /*  L = (L << 8) +  (R * next_byte) */
         ps_cab_enc_env->u4_code_int_low <<= 8;
-        ps_cab_enc_env->u4_code_int_low += (rev_next_byte * u4_range);
+        ps_cab_enc_env->u4_code_int_low += (next_byte * u4_range);
         ps_cab_enc_env->u4_bits_gen += 8;
 
         if (ps_cab_enc_env->u4_bits_gen > CABAC_BITS)
@@ -797,10 +780,8 @@ void ih264e_cabac_encode_bypass_bins(cabac_ctxt_t *ps_cabac, UWORD32 u4_bins,
     /* Update low with remaining bins and return */
     next_byte = (u4_bins & ((1 << num_bins) - 1));
 
-    REV_NBITS(next_byte, num_bins, rev_next_byte);
-
     ps_cab_enc_env->u4_code_int_low <<= num_bins;
-    ps_cab_enc_env->u4_code_int_low += (rev_next_byte * u4_range);
+    ps_cab_enc_env->u4_code_int_low += (next_byte * u4_range);
     ps_cab_enc_env->u4_bits_gen += num_bins;
 
     if (ps_cab_enc_env->u4_bits_gen > CABAC_BITS)
@@ -810,10 +791,3 @@ void ih264e_cabac_encode_bypass_bins(cabac_ctxt_t *ps_cabac, UWORD32 u4_bins,
     }
 
 }
-
-
-
-
-
-
-
diff --git a/encoder/ih264e_cabac.h b/encoder/ih264e_cabac.h
index e781783..e4722fa 100644
--- a/encoder/ih264e_cabac.h
+++ b/encoder/ih264e_cabac.h
@@ -47,24 +47,6 @@
 #define CABAC_BITS  9
 
 
-
-
-/**
-******************************************************************************
- *  @macro Count number of bits set
-******************************************************************************
-*/
-#define REV_NBITS(word, size, rev_word)               \
-{                                                     \
-    WORD32 i;                                         \
-    rev_word = 0;                                     \
-    for (i = 0; i < (size); i++)                      \
-    {                                                 \
-        UWORD32 bit = ((word) >> i) & 1;              \
-        rev_word += (1 << ((size) - i - 1)) * bit;    \
-    }                                                 \
-}                                                     \
-
 /**
 ******************************************************************************
  *  @macro Reverse bits in an unsigned integer
@@ -201,14 +183,14 @@ void ih264e_get_cabac_context(entropy_ctxt_t *ps_ent_ctxt, WORD32 u4_mb_type);
  *  @param[in]   ps_cabac_ctxt
  *  pointer to cabac context (handle)
  *
- * @returns  success or failure error code
+ * @returns  none
  *
  * @remarks
  *  None
  *
  *******************************************************************************
  */
-WORD32 ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt);
+void ih264e_cabac_flush(cabac_ctxt_t *ps_cabac_ctxt);
 
 
 /**
diff --git a/encoder/ih264e_cabac_encode.c b/encoder/ih264e_cabac_encode.c
index bf3e88e..ecc30f5 100644
--- a/encoder/ih264e_cabac_encode.c
+++ b/encoder/ih264e_cabac_encode.c
@@ -856,7 +856,7 @@ static void ih264e_cabac_write_coeff4x4(WORD16 *pi2_res_block, UWORD8 u1_nnz,
                 }
                 /* encode coeff_sign_flag[i] */
                 u1_sign = ((*pi16_coeffs) < 0) ? 1 : 0;
-                ih264e_cabac_encode_bypass_bins(ps_cabac_ctxt, u1_sign, 1);
+                ih264e_cabac_encode_bypass_bin(ps_cabac_ctxt, u1_sign);
                 i = CLZ(u4_sig_coeff);
                 i = 31 - i;
                 pi16_coeffs--;
@@ -1375,7 +1375,7 @@ static void ih264e_cabac_enc_ctx_mvd(WORD16 u1_mvd, UWORD32 u4_ctx_idx_offset,
             {
                 if (i2_sufs >= (1 << k))
                 {
-                    u4_bins = (u4_bins | (1 << i1_bins_len));
+                    u4_bins = (u4_bins | (1 << (31 - i1_bins_len)));
                     i1_bins_len++;
                     i2_sufs = i2_sufs - (1 << k);
                     k++;
@@ -1386,12 +1386,13 @@ static void ih264e_cabac_enc_ctx_mvd(WORD16 u1_mvd, UWORD32 u4_ctx_idx_offset,
                     while (k--)
                     {
                         u1_bin = ((i2_sufs >> k) & 0x01);
-                        u4_bins = (u4_bins | (u1_bin << i1_bins_len));
+                        u4_bins = (u4_bins | (u1_bin << (31 - i1_bins_len)));
                         i1_bins_len++;
                     }
                     break;
                 }
             }
+            u4_bins >>= (32 - i1_bins_len);
             ih264e_cabac_encode_bypass_bins(ps_cabac_ctxt, u4_bins,
                                             i1_bins_len);
         }
@@ -1428,9 +1429,9 @@ static void ih264e_cabac_enc_ctx_mvd(WORD16 u1_mvd, UWORD32 u4_ctx_idx_offset,
         }
         /* sign bit, uses EncodeBypass */
         if (u1_mvd > 0)
-            ih264e_cabac_encode_bypass_bins(ps_cabac_ctxt, 0, 1);
+            ih264e_cabac_encode_bypass_bin(ps_cabac_ctxt, 0);
         else
-            ih264e_cabac_encode_bypass_bins(ps_cabac_ctxt, 1, 1);
+            ih264e_cabac_encode_bypass_bin(ps_cabac_ctxt, 1);
     }
 }