mpeg2_fast_decode_block_intra()

Originally committed as revision 4146 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -72,6 +72,7 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s,
                                     DCTELEM *block, 
                                     int n);
 static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s, DCTELEM *block, int n);
+static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, DCTELEM *block, int n);
 static int mpeg_decode_motion(MpegEncContext *s, int fcode, int pred);
 static void exchange_uv(MpegEncContext *s);
 
@@ -1173,9 +1174,15 @@ static int mpeg_decode_mb(MpegEncContext *s,
 #endif
 
         if (s->codec_id == CODEC_ID_MPEG2VIDEO) {
-            for(i=0;i<mb_block_count;i++) {
-                if (mpeg2_decode_block_intra(s, s->pblocks[i], i) < 0)
-                    return -1;
+            if(s->flags2 & CODEC_FLAG2_FAST){
+                for(i=0;i<6;i++) {
+                    mpeg2_fast_decode_block_intra(s, s->pblocks[i], i);
+                }
+            }else{
+                for(i=0;i<mb_block_count;i++) {
+                    if (mpeg2_decode_block_intra(s, s->pblocks[i], i) < 0)
+                        return -1;
+                }
             }
         } else {
             for(i=0;i<6;i++) {
@@ -1928,6 +1935,76 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s,
     return 0;
 }
 
+static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, 
+                               DCTELEM *block, 
+                               int n)
+{
+    int level, dc, diff, j, run;
+    int component;
+    RLTable *rl;
+    uint8_t * scantable= s->intra_scantable.permutated;
+    const uint16_t *quant_matrix;
+    const int qscale= s->qscale;
+
+    /* DC coef */
+    if (n < 4){
+        quant_matrix = s->intra_matrix;
+        component = 0; 
+    }else{
+        quant_matrix = s->chroma_intra_matrix;
+        component = (n&1) + 1;
+    }
+    diff = decode_dc(&s->gb, component);
+    if (diff >= 0xffff)
+        return -1;
+    dc = s->last_dc[component];
+    dc += diff;
+    s->last_dc[component] = dc;
+    block[0] = dc << (3 - s->intra_dc_precision);
+    if (s->intra_vlc_format)
+        rl = &rl_mpeg2;
+    else
+        rl = &rl_mpeg1;
+
+    {
+        OPEN_READER(re, &s->gb);    
+        /* 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) {
+                scantable += run;
+                j = *scantable;
+                level= (level*qscale*quant_matrix[j])>>4;
+                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
+                LAST_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, 12); SKIP_BITS(re, &s->gb, 12);
+                scantable += run;
+                j = *scantable;
+                if(level<0){
+                    level= (-level*qscale*quant_matrix[j])>>4;
+                    level= -level;
+                }else{
+                    level= (level*qscale*quant_matrix[j])>>4;
+                }
+            }
+            
+            block[j] = level;
+        }
+        CLOSE_READER(re, &s->gb);
+    }
+    
+    s->block_last_index[n] = scantable - s->intra_scantable.permutated;
+    return 0;
+}
+
 typedef struct Mpeg1Context {
     MpegEncContext mpeg_enc_ctx;
     int mpeg_enc_ctx_allocated; /* true if decoding context allocated */