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authorMichael Niedermayer <michaelni@gmx.at>2004-10-30 01:43:37 +0000
committerMichael Niedermayer <michaelni@gmx.at>2004-10-30 01:43:37 +0000
commit672a19aac24f94d4a55394099596a84add67c39b (patch)
tree1761e80c64a703a0b93d8b62298a30accb543231 /libavcodec/rangecoder.h
parent9287acd1970986de093578c6724c8ba1877c7485 (diff)
downloadffmpeg-672a19aac24f94d4a55394099596a84add67c39b.tar.gz
range coder
Originally committed as revision 3654 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/rangecoder.h')
-rw-r--r--libavcodec/rangecoder.h129
1 files changed, 129 insertions, 0 deletions
diff --git a/libavcodec/rangecoder.h b/libavcodec/rangecoder.h
new file mode 100644
index 0000000000..3c363ac32c
--- /dev/null
+++ b/libavcodec/rangecoder.h
@@ -0,0 +1,129 @@
+/*
+ * Range coder
+ * Copyright (c) 2004 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 rangecoder.h
+ * Range coder.
+ */
+
+
+#undef NDEBUG
+#include <assert.h>
+
+typedef struct RangeCoder{
+ int low;
+ int range;
+ int outstanding_count;
+ int outstanding_byte;
+ uint8_t zero_state[256];
+ uint8_t one_state[256];
+ uint8_t *bytestream_start;
+ uint8_t *bytestream;
+ uint8_t *bytestream_end;
+}RangeCoder;
+
+void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
+void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
+int ff_rac_terminate(RangeCoder *c);
+void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
+
+static inline void renorm_encoder(RangeCoder *c){
+ //FIXME optimize
+ while(c->range < 0x100){
+ if(c->outstanding_byte < 0){
+ c->outstanding_byte= c->low>>8;
+ }else if(c->low <= 0xFF00){
+ *c->bytestream++ = c->outstanding_byte;
+ for(;c->outstanding_count; c->outstanding_count--)
+ *c->bytestream++ = 0xFF;
+ c->outstanding_byte= c->low>>8;
+ }else if(c->low >= 0x10000){
+ *c->bytestream++ = c->outstanding_byte + 1;
+ for(;c->outstanding_count; c->outstanding_count--)
+ *c->bytestream++ = 0x00;
+ c->outstanding_byte= (c->low>>8) & 0xFF;
+ }else{
+ c->outstanding_count++;
+ }
+
+ c->low = (c->low & 0xFF)<<8;
+ c->range <<= 8;
+ }
+}
+
+static inline void put_rac(RangeCoder *c, uint8_t * const state, int bit){
+ int range1= (c->range * (*state)) >> 8;
+
+ assert(*state);
+ assert(range1 < c->range);
+ assert(range1 > 0);
+ if(!bit){
+ c->range -= range1;
+ *state= c->zero_state[*state];
+ }else{
+ c->low += c->range - range1;
+ c->range = range1;
+ *state= c->one_state[*state];
+ }
+
+ renorm_encoder(c);
+}
+
+static inline void refill(RangeCoder *c){
+ if(c->range < 0x100){
+ c->range <<= 8;
+ c->low <<= 8;
+ if(c->bytestream < c->bytestream_end)
+ c->low+= c->bytestream[0];
+ c->bytestream++;
+ }
+}
+
+static inline int get_rac(RangeCoder *c, uint8_t * const state){
+ int range1= (c->range * (*state)) >> 8;
+ int one_mask;
+
+ c->range -= range1;
+#if 1
+ if(c->low < c->range){
+ *state= c->zero_state[*state];
+ refill(c);
+ return 0;
+ }else{
+ c->low -= c->range;
+ *state= c->one_state[*state];
+ c->range = range1;
+ refill(c);
+ return 1;
+ }
+#else
+ one_mask= (c->range - c->low-1)>>31;
+
+ c->low -= c->range & one_mask;
+ c->range += (range1 - c->range) & one_mask;
+
+ *state= c->zero_state[(*state) + (256&one_mask)];
+
+ refill(c);
+
+ return one_mask&1;
+#endif
+}
+