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

libavcodec/cabac.c

+/*
+ * 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.c
+ * Context Adaptive Binary Arithmetic Coder.
+ */
+
+#include <string.h>
+
+#include "common.h"
+#include "cabac.h"
+
+const uint8_t ff_h264_lps_range[64][4]= {
+{128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
+{116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
+{ 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
+{ 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
+{ 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
+{ 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
+{ 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
+{ 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
+{ 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
+{ 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
+{ 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
+{ 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
+{ 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
+{ 10, 12, 14, 16}, {  9, 11, 13, 15}, {  9, 11, 12, 14}, {  8, 10, 12, 14},
+{  8,  9, 11, 13}, {  7,  9, 11, 12}, {  7,  9, 10, 12}, {  7,  8, 10, 11},
+{  6,  8,  9, 11}, {  6,  7,  9, 10}, {  6,  7,  8,  9}, {  2,  2,  2,  2},
+};
+
+const uint8_t ff_h264_mps_state[64]= {
+  1, 2, 3, 4, 5, 6, 7, 8,
+  9,10,11,12,13,14,15,16,
+ 17,18,19,20,21,22,23,24,
+ 25,26,27,28,29,30,31,32,
+ 33,34,35,36,37,38,39,40,
+ 41,42,43,44,45,46,47,48,
+ 49,50,51,52,53,54,55,56,
+ 57,58,59,60,61,62,62,63,
+};
+
+const uint8_t ff_h264_lps_state[64]= {
+  0, 0, 1, 2, 2, 4, 4, 5,
+  6, 7, 8, 9, 9,11,11,12,
+ 13,13,15,15,16,16,18,18,
+ 19,19,21,21,22,22,23,24,
+ 24,25,26,26,27,27,28,29,
+ 29,30,30,30,31,32,32,33,
+ 33,33,34,34,35,35,35,36,
+ 36,36,37,37,37,38,38,63,
+};
+
+/**
+ *
+ * @param buf_size size of buf in bits
+ */
+void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
+    init_put_bits(&c->pb, buf, buf_size, NULL, NULL);
+
+    c->low= 0;
+    c->range= 0x1FE;
+    c->outstanding_count= 0;
+#ifdef STRICT_LIMITS
+    c->sym_count =0;
+#endif
+    
+    c->pb.bit_left++; //avoids firstBitFlag
+}
+
+/**
+ *
+ * @param buf_size size of buf in bits
+ */
+void ff_init_cabac_decoder(CABACContext *c, uint8_t *buf, int buf_size){
+    c->bytestream= buf;
+
+    c->low= *c->bytestream++;
+    c->low= (c->low<<9) + ((*c->bytestream++)<<1);
+    c->range= 0x1FE00;
+    c->bits_left= 7;
+}
+
+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){
+    int i, j;
+    
+    for(i=0; i<state_count; i++){
+        for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
+            c->lps_range[2*i+0][j]=
+            c->lps_range[2*i+1][j]= lps_range[i][j];
+        }
+
+        c->mps_state[2*i+0]= 2*mps_state[i];
+        c->mps_state[2*i+1]= 2*mps_state[i]+1;
+
+        if(lps_state[i]){
+            c->lps_state[2*i+0]= 2*lps_state[i];
+            c->lps_state[2*i+1]= 2*lps_state[i]+1;
+        }else{
+            c->lps_state[2*i+0]= 1;
+            c->lps_state[2*i+1]= 0;
+        }
+    }
+}
+
+#if 0 //selftest
+#define SIZE 10240
+int main(){
+    CABACContext c;
+    uint8_t b[9*SIZE];
+    uint8_t bit[9*SIZE];
+    int i;
+    uint8_t state= 0;
+    
+    ff_init_cabac_encoder(&c, b, SIZE);
+    ff_init_cabac_states(&c, ff_h264_lps_range, ff_h264_mps_state, ff_h264_lps_state, 64);
+    
+    for(i=0; i<SIZE; i++){
+        bit[i]= (random()%7)&1;
+    }
+    
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        put_cabac_bypass(&c, bit[i]);
+STOP_TIMER("put_cabac_bypass")
+    }
+    
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        put_cabac(&c, &state, bit[i]);
+STOP_TIMER("put_cabac")
+    }
+
+    put_cabac_terminate(&c, 1);
+    
+    ff_init_cabac_decoder(&c, b, SIZE);
+    
+    state=0;
+    
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        if( bit[i] != get_cabac_bypass(&c) )
+            printf("CABAC bypass failure at %d\n", i);
+STOP_TIMER("get_cabac_bypass")
+    }
+    
+    for(i=0; i<SIZE; i++){
+START_TIMER
+        if( bit[i] != get_cabac(&c, &state) )
+            printf("CABAC failure at %d\n", i);
+STOP_TIMER("get_cabac")
+    }
+    
+    if(!get_cabac_terminate(&c))
+        printf("where's the Terminator?\n");
+    
+    return 0;
+}
+
+#endif

libavcodec/cabac.h

+/*
+ * 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;
+    }    
+}
+