optimizing non_intra ac coeff decode

Originally committed as revision 4140 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c
index 78ba9c7..c912c45 100644 (file)
--- a/libavcodec/mpeg12.c
+++ b/libavcodec/mpeg12.c
@@ -1564,45 +1564,42 @@ static inline int mpeg1_decode_block_inter(MpegEncContext *s,
     const int qscale= s->qscale;
 
     {
-        int v;
         OPEN_READER(re, &s->gb);
         i = -1;
         /* special case for the first coef. no need to add a second vlc table */
         UPDATE_CACHE(re, &s->gb);
-        v= SHOW_UBITS(re, &s->gb, 2);
-        if (v & 2) {
-            LAST_SKIP_BITS(re, &s->gb, 2);
+        if (((int32_t)GET_CACHE(re, &s->gb)) < 0) {
             level= (3*qscale*quant_matrix[0])>>5;
             level= (level-1)|1;
-            if(v&1)
+            if(GET_CACHE(re, &s->gb)&0x40000000)
                 level= -level;
             block[0] = level;
             i++;
+            SKIP_BITS(re, &s->gb, 2);
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                goto end;
         }
 
         /* now quantify & encode AC coefs */
         for(;;) {
-            UPDATE_CACHE(re, &s->gb);
             GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
             
-            if(level == 127){
-                break;
-            } else if(level != 0) {
+            if(level != 0) {
                 i += run;
                 j = scantable[i];
                 level= ((level*2+1)*qscale*quant_matrix[j])>>5;
                 level= (level-1)|1;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
-                LAST_SKIP_BITS(re, &s->gb, 1);
+                SKIP_BITS(re, &s->gb, 1);
             } else {
                 /* escape */
                 run = SHOW_UBITS(re, &s->gb, 6)+1; LAST_SKIP_BITS(re, &s->gb, 6);
                 UPDATE_CACHE(re, &s->gb);
                 level = SHOW_SBITS(re, &s->gb, 8); SKIP_BITS(re, &s->gb, 8);
                 if (level == -128) {
-                    level = SHOW_UBITS(re, &s->gb, 8) - 256; LAST_SKIP_BITS(re, &s->gb, 8);
+                    level = SHOW_UBITS(re, &s->gb, 8) - 256; SKIP_BITS(re, &s->gb, 8);
                 } else if (level == 0) {
-                    level = SHOW_UBITS(re, &s->gb, 8)      ; LAST_SKIP_BITS(re, &s->gb, 8);
+                    level = SHOW_UBITS(re, &s->gb, 8)      ; SKIP_BITS(re, &s->gb, 8);
                 }
                 i += run;
                 j = scantable[i];
@@ -1622,7 +1619,12 @@ static inline int mpeg1_decode_block_inter(MpegEncContext *s,
             }
 
             block[j] = level;
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                break;
+            UPDATE_CACHE(re, &s->gb);
         }
+end:
+        LAST_SKIP_BITS(re, &s->gb, 2);
         CLOSE_READER(re, &s->gb);
     }
     s->block_last_index[n] = i;
@@ -1637,45 +1639,42 @@ static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *bloc
     const int qscale= s->qscale;
 
     {
-        int v;
         OPEN_READER(re, &s->gb);
         i = -1;
         /* special case for the first coef. no need to add a second vlc table */
         UPDATE_CACHE(re, &s->gb);
-        v= SHOW_UBITS(re, &s->gb, 2);
-        if (v & 2) {
-            LAST_SKIP_BITS(re, &s->gb, 2);
+        if (((int32_t)GET_CACHE(re, &s->gb)) < 0) {
             level= (3*qscale)>>1;
             level= (level-1)|1;
-            if(v&1)
+            if(GET_CACHE(re, &s->gb)&0x40000000)
                 level= -level;
             block[0] = level;
             i++;
+            SKIP_BITS(re, &s->gb, 2);
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                goto end;
         }
 
         /* now quantify & encode AC coefs */
         for(;;) {
-            UPDATE_CACHE(re, &s->gb);
             GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
             
-            if(level == 127){
-                break;
-            } else if(level != 0) {
+            if(level != 0) {
                 i += run;
                 j = scantable[i];
                 level= ((level*2+1)*qscale)>>1;
                 level= (level-1)|1;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
-                LAST_SKIP_BITS(re, &s->gb, 1);
+                SKIP_BITS(re, &s->gb, 1);
             } else {
                 /* escape */
                 run = SHOW_UBITS(re, &s->gb, 6)+1; LAST_SKIP_BITS(re, &s->gb, 6);
                 UPDATE_CACHE(re, &s->gb);
                 level = SHOW_SBITS(re, &s->gb, 8); SKIP_BITS(re, &s->gb, 8);
                 if (level == -128) {
-                    level = SHOW_UBITS(re, &s->gb, 8) - 256; LAST_SKIP_BITS(re, &s->gb, 8);
+                    level = SHOW_UBITS(re, &s->gb, 8) - 256; SKIP_BITS(re, &s->gb, 8);
                 } else if (level == 0) {
-                    level = SHOW_UBITS(re, &s->gb, 8)      ; LAST_SKIP_BITS(re, &s->gb, 8);
+                    level = SHOW_UBITS(re, &s->gb, 8)      ; SKIP_BITS(re, &s->gb, 8);
                 }
                 i += run;
                 j = scantable[i];
@@ -1691,7 +1690,12 @@ static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *bloc
             }
 
             block[j] = level;
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                break;
+            UPDATE_CACHE(re, &s->gb);
         }
+end:
+        LAST_SKIP_BITS(re, &s->gb, 2);
         CLOSE_READER(re, &s->gb);
     }
     s->block_last_index[n] = i;
@@ -1713,7 +1717,6 @@ static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
     mismatch = 1;
 
     {
-        int v;
         OPEN_READER(re, &s->gb);
         i = -1;
         if (n < 4)
@@ -1723,30 +1726,28 @@ static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
 
         /* special case for the first coef. no need to add a second vlc table */
         UPDATE_CACHE(re, &s->gb);
-        v= SHOW_UBITS(re, &s->gb, 2);
-        if (v & 2) {
-            LAST_SKIP_BITS(re, &s->gb, 2);
+        if (((int32_t)GET_CACHE(re, &s->gb)) < 0) {
             level= (3*qscale*quant_matrix[0])>>5;
-            if(v&1)
+            if(GET_CACHE(re, &s->gb)&0x40000000)
                 level= -level;
             block[0] = level;
             mismatch ^= level;
             i++;
+            SKIP_BITS(re, &s->gb, 2);
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                goto end;
         }
 
         /* now quantify & encode AC coefs */
         for(;;) {
-            UPDATE_CACHE(re, &s->gb);
             GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
             
-            if(level == 127){
-                break;
-            } else if(level != 0) {
+            if(level != 0) {
                 i += run;
                 j = scantable[i];
                 level= ((level*2+1)*qscale*quant_matrix[j])>>5;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
-                LAST_SKIP_BITS(re, &s->gb, 1);
+                SKIP_BITS(re, &s->gb, 1);
             } else {
                 /* escape */
                 run = SHOW_UBITS(re, &s->gb, 6)+1; LAST_SKIP_BITS(re, &s->gb, 6);
@@ -1769,7 +1770,12 @@ static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
             
             mismatch ^= level;
             block[j] = level;
+            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+                break;
+            UPDATE_CACHE(re, &s->gb);
         }
+end:
+        LAST_SKIP_BITS(re, &s->gb, 2);
         CLOSE_READER(re, &s->gb);
     }
     block[63] ^= (mismatch & 1);
@@ -1792,29 +1798,27 @@ static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
 
     /* special case for the first coef. no need to add a second vlc table */
     UPDATE_CACHE(re, &s->gb);
-    v= SHOW_UBITS(re, &s->gb, 2);
-    if (v & 2) {
-        LAST_SKIP_BITS(re, &s->gb, 2);
+    if (((int32_t)GET_CACHE(re, &s->gb)) < 0) {
         level= (3*qscale)>>1;
-        if(v&1)
+        if(GET_CACHE(re, &s->gb)&0x40000000)
             level= -level;
         block[0] = level;
         i++;
+        SKIP_BITS(re, &s->gb, 2);
+        if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+            goto end;
     }
 
     /* now quantify & encode AC coefs */
     for(;;) {
-        UPDATE_CACHE(re, &s->gb);
         GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
         
-        if(level == 127){
-            break;
-        } else if(level != 0) {
+        if(level != 0) {
             i += run;
             j = scantable[i];
             level= ((level*2+1)*qscale)>>1;
             level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
-            LAST_SKIP_BITS(re, &s->gb, 1);
+            SKIP_BITS(re, &s->gb, 1);
         } else {
             /* escape */
             run = SHOW_UBITS(re, &s->gb, 6)+1; LAST_SKIP_BITS(re, &s->gb, 6);
@@ -1832,7 +1836,12 @@ static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
         }
         
         block[j] = level;
+        if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
+            break;
+        UPDATE_CACHE(re, &s->gb);
     }
+end:
+    LAST_SKIP_BITS(re, &s->gb, 2);    
     CLOSE_READER(re, &s->gb);
     s->block_last_index[n] = i;
     return 0;