CABAC

note, this is just the CABAC (de)coder not complete h264-cabac support

Originally committed as revision 1915 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 232 insertions, 0 deletions

diff --git a/libavcodec/cabac.h b/libavcodec/cabac.h
new file mode 100644
index 0000000000..69f6697688
--- /dev/null
+++ b/libavcodec/cabac.h
@@ -0,0 +1,232 @@
+/*
+ * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
+ * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+ 
+/**
+ * @file cabac.h
+ * Context Adaptive Binary Arithmetic Coder.
+ */
+
+
+#undef NDEBUG
+#include <assert.h>
+
+typedef struct CABACContext{
+    int low;
+    int range;
+    int outstanding_count;
+#ifdef STRICT_LIMITS
+    int symCount;
+#endif
+    uint8_t lps_range[2*64][4];   ///< rangeTabLPS
+    uint8_t lps_state[2*64];      ///< transIdxLPS
+    uint8_t mps_state[2*64];      ///< transIdxMPS
+    uint8_t *bytestream;
+    int bits_left;                ///<
+    PutBitContext pb;
+}CABACContext;
+
+const uint8_t ff_h264_lps_range[64][4];
+const uint8_t ff_h264_mps_state[64];
+const uint8_t ff_h264_lps_state[64];
+
+void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
+void ff_init_cabac_decoder(CABACContext *c, uint8_t *buf, int buf_size);
+void ff_init_cabac_states(CABACContext *c, uint8_t const (*lps_range)[4], 
+                          uint8_t const *mps_state, uint8_t const *lps_state, int state_count);
+
+
+static inline void put_cabac_bit(CABACContext *c, int b){
+    put_bits(&c->pb, 1, b); 
+    for(;c->outstanding_count; c->outstanding_count--){ 
+        put_bits(&c->pb, 1, 1-b);
+    }
+}
+
+static inline void renorm_cabac_encoder(CABACContext *c){
+    while(c->range < 0x100){
+        //FIXME optimize
+        if(c->low<0x100){
+            put_cabac_bit(c, 0);
+        }else if(c->low<0x200){
+            c->outstanding_count++;
+            c->low -= 0x100;
+        }else{
+            put_cabac_bit(c, 1);
+            c->low -= 0x200;
+        }
+        
+        c->range+= c->range;
+        c->low += c->low;
+    }
+}
+
+static inline void put_cabac(CABACContext *c, uint8_t * const state, int bit){
+    int RangeLPS= c->lps_range[*state][((c->range)>>6)&3];
+    
+    if(bit == ((*state)&1)){
+        c->range -= RangeLPS;
+        *state= c->mps_state[*state];
+    }else{
+        c->low += c->range - RangeLPS;
+        c->range = RangeLPS;
+        *state= c->lps_state[*state];
+    }
+    
+    renorm_cabac_encoder(c);
+
+#ifdef STRICT_LIMITS
+    c->symCount++;
+#endif
+}
+
+static inline void put_cabac_static(CABACContext *c, int RangeLPS, int bit){
+    assert(c->range > RangeLPS);
+
+    if(!bit){
+        c->range -= RangeLPS;
+    }else{
+        c->low += c->range - RangeLPS;
+        c->range = RangeLPS;
+    }
+
+    renorm_cabac_encoder(c);
+
+#ifdef STRICT_LIMITS
+    c->symCount++;
+#endif
+}
+
+static inline void put_cabac_bypass(CABACContext *c, int bit){
+    c->low += c->low;
+
+    if(bit){
+        c->low += c->range;
+    }
+//FIXME optimize
+    if(c->low<0x200){
+        put_cabac_bit(c, 0);
+    }else if(c->low<0x400){
+        c->outstanding_count++;
+        c->low -= 0x200;
+    }else{
+        put_cabac_bit(c, 1);
+        c->low -= 0x400;
+    }
+        
+#ifdef STRICT_LIMITS
+    c->symCount++;
+#endif
+}
+
+static inline void put_cabac_terminate(CABACContext *c, int bit){
+    c->range -= 2;
+
+    if(!bit){
+        renorm_cabac_encoder(c);
+    }else{
+        c->low += c->range;
+        c->range= 2;
+        
+        renorm_cabac_encoder(c);
+
+        assert(c->low <= 0x1FF);
+        put_cabac_bit(c, c->low>>9);
+        put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
+        
+        flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
+    }
+        
+#ifdef STRICT_LIMITS
+    c->symCount++;
+#endif
+}
+
+static inline void renorm_cabac_decoder(CABACContext *c){
+    while(c->range < 0x10000){
+        c->range+= c->range;
+        c->low+= c->low;
+        if(--c->bits_left == 0){
+            c->low+= *c->bytestream++;
+            c->bits_left= 8;
+        }
+    }
+}
+
+static inline int get_cabac(CABACContext *c, uint8_t * const state){
+    int RangeLPS= c->lps_range[*state][((c->range)>>14)&3]<<8;
+    int bit;
+    
+    c->range -= RangeLPS;
+    if(c->low < c->range){
+        bit= (*state)&1;
+        *state= c->mps_state[*state];
+    }else{
+        bit= ((*state)&1)^1;
+        c->low -= c->range;
+        c->range = RangeLPS;
+        *state= c->lps_state[*state];
+    }
+    renorm_cabac_decoder(c);
+    
+    return bit;    
+}
+
+static inline int get_cabac_static(CABACContext *c, int RangeLPS){
+    int bit;
+    
+    c->range -= RangeLPS;
+    if(c->low < c->range){
+        bit= 0;
+    }else{
+        bit= 1;
+        c->low -= c->range;
+        c->range = RangeLPS;
+    }
+    renorm_cabac_decoder(c);
+    
+    return bit;    
+}
+
+static inline int get_cabac_bypass(CABACContext *c){
+    c->low += c->low;
+
+    if(--c->bits_left == 0){
+        c->low+= *c->bytestream++;
+        c->bits_left= 8;
+    }
+    
+    if(c->low < c->range){
+        return 0;
+    }else{
+        c->low -= c->range;
+        return 1;
+    }
+}
+
+static inline int get_cabac_terminate(CABACContext *c){
+    c->range -= 2<<8;
+    if(c->low < c->range){
+        renorm_cabac_decoder(c);    
+        return 0;
+    }else{
+        return 1;
+    }    
+}
+