Clone decode_cabac_residual() for DC residuals, to get rid of a bunch of branches in the main loop.

Originally committed as revision 14050 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -5337,24 +5337,28 @@ static int decode_cabac_mb_mvd( H264Context *h, int list, int n, int l ) {
     return get_cabac_bypass_sign( &h->cabac, -mvd );
 }
 
-static inline int get_cabac_cbf_ctx( H264Context *h, int cat, int idx ) {
+static av_always_inline int get_cabac_cbf_ctx( H264Context *h, int cat, int idx, int is_dc ) {
     int nza, nzb;
     int ctx = 0;
 
+    if( is_dc ) {
     if( cat == 0 ) {
         nza = h->left_cbp&0x100;
         nzb = h-> top_cbp&0x100;
-    } else if( cat == 1 || cat == 2 ) {
-        nza = h->non_zero_count_cache[scan8[idx] - 1];
-        nzb = h->non_zero_count_cache[scan8[idx] - 8];
-    } else if( cat == 3 ) {
+    } else {
         nza = (h->left_cbp>>(6+idx))&0x01;
         nzb = (h-> top_cbp>>(6+idx))&0x01;
+    }
+    } else {
+    if( cat == 1 || cat == 2 ) {
+        nza = h->non_zero_count_cache[scan8[idx] - 1];
+        nzb = h->non_zero_count_cache[scan8[idx] - 8];
     } else {
         assert(cat == 4);
         nza = h->non_zero_count_cache[scan8[16+idx] - 1];
         nzb = h->non_zero_count_cache[scan8[16+idx] - 8];
     }
+    }
 
     if( nza > 0 )
         ctx++;
@@ -5372,7 +5376,7 @@ DECLARE_ASM_CONST(1, uint8_t, last_coeff_flag_offset_8x8[63]) = {
     5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8
 };
 
-static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int n, const uint8_t *scantable, const uint32_t *qmul, int max_coeff) {
+static av_always_inline void decode_cabac_residual_internal( H264Context *h, DCTELEM *block, int cat, int n, const uint8_t *scantable, const uint32_t *qmul, int max_coeff, int is_dc ) {
     static const int significant_coeff_flag_offset[2][6] = {
       { 105+0, 105+15, 105+29, 105+44, 105+47, 402 },
       { 277+0, 277+15, 277+29, 277+44, 277+47, 436 }
@@ -5440,12 +5444,15 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
      */
 
     /* read coded block flag */
-    if( cat != 5 ) {
-        if( get_cabac( CC, &h->cabac_state[85 + get_cabac_cbf_ctx( h, cat, n ) ] ) == 0 ) {
+    if( is_dc || cat != 5 ) {
+        if( get_cabac( CC, &h->cabac_state[85 + get_cabac_cbf_ctx( h, cat, n, is_dc ) ] ) == 0 ) {
+            if( !is_dc ) {
             if( cat == 1 || cat == 2 )
                 h->non_zero_count_cache[scan8[n]] = 0;
-            else if( cat == 4 )
+            else
                 h->non_zero_count_cache[scan8[16+n]] = 0;
+            }
+
 #ifdef CABAC_ON_STACK
             h->cabac.range     = cc.range     ;
             h->cabac.low       = cc.low       ;
@@ -5462,7 +5469,7 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
     abs_level_m1_ctx_base = h->cabac_state
         + coeff_abs_level_m1_offset[cat];
 
-    if( cat == 5 ) {
+    if( !is_dc && cat == 5 ) {
 #define DECODE_SIGNIFICANCE( coefs, sig_off, last_off ) \
         for(last= 0; last < coefs; last++) { \
             uint8_t *sig_ctx = significant_coeff_ctx_base + sig_off; \
@@ -5491,18 +5498,21 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
     }
     assert(coeff_count > 0);
 
+    if( is_dc ) {
     if( cat == 0 )
         h->cbp_table[h->mb_xy] |= 0x100;
-    else if( cat == 1 || cat == 2 )
-        h->non_zero_count_cache[scan8[n]] = coeff_count;
-    else if( cat == 3 )
+    else
         h->cbp_table[h->mb_xy] |= 0x40 << n;
+    } else {
+    if( cat == 1 || cat == 2 )
+        h->non_zero_count_cache[scan8[n]] = coeff_count;
     else if( cat == 4 )
         h->non_zero_count_cache[scan8[16+n]] = coeff_count;
     else {
         assert( cat == 5 );
         fill_rectangle(&h->non_zero_count_cache[scan8[n]], 2, 2, 8, coeff_count, 1);
     }
+    }
 
     for( coeff_count--; coeff_count >= 0; coeff_count-- ) {
         uint8_t *ctx = coeff_abs_level1_ctx[node_ctx] + abs_level_m1_ctx_base;
@@ -5511,7 +5521,7 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
 
         if( get_cabac( CC, ctx ) == 0 ) {
             node_ctx = coeff_abs_level_transition[0][node_ctx];
-            if( !qmul ) {
+            if( is_dc ) {
                 block[j] = get_cabac_bypass_sign( CC, -1);
             }else{
                 block[j] = (get_cabac_bypass_sign( CC, -qmul[j]) + 32) >> 6;
@@ -5538,7 +5548,7 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
                 coeff_abs+= 14;
             }
 
-            if( !qmul ) {
+            if( is_dc ) {
                 if( get_cabac_bypass( CC ) ) block[j] = -coeff_abs;
                 else                                block[j] =  coeff_abs;
             }else{
@@ -5555,6 +5565,25 @@ static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int
 
 }
 
+#ifndef CONFIG_SMALL
+static void decode_cabac_residual_dc( H264Context *h, DCTELEM *block, int cat, int n, const uint8_t *scantable, const uint32_t *qmul, int max_coeff ) {
+    decode_cabac_residual_internal(h, block, cat, n, scantable, qmul, max_coeff, 1);
+}
+
+static void decode_cabac_residual_nondc( H264Context *h, DCTELEM *block, int cat, int n, const uint8_t *scantable, const uint32_t *qmul, int max_coeff ) {
+    decode_cabac_residual_internal(h, block, cat, n, scantable, qmul, max_coeff, 0);
+}
+#endif
+
+static void decode_cabac_residual( H264Context *h, DCTELEM *block, int cat, int n, const uint8_t *scantable, const uint32_t *qmul, int max_coeff ) {
+#ifdef CONFIG_SMALL
+    decode_cabac_residual_internal(h, block, cat, n, scantable, qmul, max_coeff, cat == 0 || cat == 3);
+#else
+    if( cat == 0 || cat == 3 ) decode_cabac_residual_dc(h, block, cat, n, scantable, qmul, max_coeff);
+    else decode_cabac_residual_nondc(h, block, cat, n, scantable, qmul, max_coeff);
+#endif
+}
+
 static inline void compute_mb_neighbors(H264Context *h)
 {
     MpegEncContext * const s = &h->s;