Chris@69: /* Copyright (c) 2001-2011 Timothy B. Terriberry
Chris@69:    Copyright (c) 2008-2009 Xiph.Org Foundation */
Chris@69: /*
Chris@69:    Redistribution and use in source and binary forms, with or without
Chris@69:    modification, are permitted provided that the following conditions
Chris@69:    are met:
Chris@69: 
Chris@69:    - Redistributions of source code must retain the above copyright
Chris@69:    notice, this list of conditions and the following disclaimer.
Chris@69: 
Chris@69:    - Redistributions in binary form must reproduce the above copyright
Chris@69:    notice, this list of conditions and the following disclaimer in the
Chris@69:    documentation and/or other materials provided with the distribution.
Chris@69: 
Chris@69:    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
Chris@69:    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
Chris@69:    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
Chris@69:    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
Chris@69:    OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
Chris@69:    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
Chris@69:    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
Chris@69:    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
Chris@69:    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
Chris@69:    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
Chris@69:    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Chris@69: */
Chris@69: 
Chris@69: #if defined(HAVE_CONFIG_H)
Chris@69: # include "config.h"
Chris@69: #endif
Chris@69: #include "os_support.h"
Chris@69: #include "arch.h"
Chris@69: #include "entenc.h"
Chris@69: #include "mfrngcod.h"
Chris@69: 
Chris@69: /*A range encoder.
Chris@69:   See entdec.c and the references for implementation details \cite{Mar79,MNW98}.
Chris@69: 
Chris@69:   @INPROCEEDINGS{Mar79,
Chris@69:    author="Martin, G.N.N.",
Chris@69:    title="Range encoding: an algorithm for removing redundancy from a digitised
Chris@69:     message",
Chris@69:    booktitle="Video \& Data Recording Conference",
Chris@69:    year=1979,
Chris@69:    address="Southampton",
Chris@69:    month=Jul
Chris@69:   }
Chris@69:   @ARTICLE{MNW98,
Chris@69:    author="Alistair Moffat and Radford Neal and Ian H. Witten",
Chris@69:    title="Arithmetic Coding Revisited",
Chris@69:    journal="{ACM} Transactions on Information Systems",
Chris@69:    year=1998,
Chris@69:    volume=16,
Chris@69:    number=3,
Chris@69:    pages="256--294",
Chris@69:    month=Jul,
Chris@69:    URL="http://www.stanford.edu/class/ee398/handouts/papers/Moffat98ArithmCoding.pdf"
Chris@69:   }*/
Chris@69: 
Chris@69: static int ec_write_byte(ec_enc *_this,unsigned _value){
Chris@69:   if(_this->offs+_this->end_offs>=_this->storage)return -1;
Chris@69:   _this->buf[_this->offs++]=(unsigned char)_value;
Chris@69:   return 0;
Chris@69: }
Chris@69: 
Chris@69: static int ec_write_byte_at_end(ec_enc *_this,unsigned _value){
Chris@69:   if(_this->offs+_this->end_offs>=_this->storage)return -1;
Chris@69:   _this->buf[_this->storage-++(_this->end_offs)]=(unsigned char)_value;
Chris@69:   return 0;
Chris@69: }
Chris@69: 
Chris@69: /*Outputs a symbol, with a carry bit.
Chris@69:   If there is a potential to propagate a carry over several symbols, they are
Chris@69:    buffered until it can be determined whether or not an actual carry will
Chris@69:    occur.
Chris@69:   If the counter for the buffered symbols overflows, then the stream becomes
Chris@69:    undecodable.
Chris@69:   This gives a theoretical limit of a few billion symbols in a single packet on
Chris@69:    32-bit systems.
Chris@69:   The alternative is to truncate the range in order to force a carry, but
Chris@69:    requires similar carry tracking in the decoder, needlessly slowing it down.*/
Chris@69: static void ec_enc_carry_out(ec_enc *_this,int _c){
Chris@69:   if(_c!=EC_SYM_MAX){
Chris@69:     /*No further carry propagation possible, flush buffer.*/
Chris@69:     int carry;
Chris@69:     carry=_c>>EC_SYM_BITS;
Chris@69:     /*Don't output a byte on the first write.
Chris@69:       This compare should be taken care of by branch-prediction thereafter.*/
Chris@69:     if(_this->rem>=0)_this->error|=ec_write_byte(_this,_this->rem+carry);
Chris@69:     if(_this->ext>0){
Chris@69:       unsigned sym;
Chris@69:       sym=(EC_SYM_MAX+carry)&EC_SYM_MAX;
Chris@69:       do _this->error|=ec_write_byte(_this,sym);
Chris@69:       while(--(_this->ext)>0);
Chris@69:     }
Chris@69:     _this->rem=_c&EC_SYM_MAX;
Chris@69:   }
Chris@69:   else _this->ext++;
Chris@69: }
Chris@69: 
Chris@69: static OPUS_INLINE void ec_enc_normalize(ec_enc *_this){
Chris@69:   /*If the range is too small, output some bits and rescale it.*/
Chris@69:   while(_this->rng<=EC_CODE_BOT){
Chris@69:     ec_enc_carry_out(_this,(int)(_this->val>>EC_CODE_SHIFT));
Chris@69:     /*Move the next-to-high-order symbol into the high-order position.*/
Chris@69:     _this->val=(_this->val<<EC_SYM_BITS)&(EC_CODE_TOP-1);
Chris@69:     _this->rng<<=EC_SYM_BITS;
Chris@69:     _this->nbits_total+=EC_SYM_BITS;
Chris@69:   }
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_init(ec_enc *_this,unsigned char *_buf,opus_uint32 _size){
Chris@69:   _this->buf=_buf;
Chris@69:   _this->end_offs=0;
Chris@69:   _this->end_window=0;
Chris@69:   _this->nend_bits=0;
Chris@69:   /*This is the offset from which ec_tell() will subtract partial bits.*/
Chris@69:   _this->nbits_total=EC_CODE_BITS+1;
Chris@69:   _this->offs=0;
Chris@69:   _this->rng=EC_CODE_TOP;
Chris@69:   _this->rem=-1;
Chris@69:   _this->val=0;
Chris@69:   _this->ext=0;
Chris@69:   _this->storage=_size;
Chris@69:   _this->error=0;
Chris@69: }
Chris@69: 
Chris@69: void ec_encode(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _ft){
Chris@69:   opus_uint32 r;
Chris@69:   r=celt_udiv(_this->rng,_ft);
Chris@69:   if(_fl>0){
Chris@69:     _this->val+=_this->rng-IMUL32(r,(_ft-_fl));
Chris@69:     _this->rng=IMUL32(r,(_fh-_fl));
Chris@69:   }
Chris@69:   else _this->rng-=IMUL32(r,(_ft-_fh));
Chris@69:   ec_enc_normalize(_this);
Chris@69: }
Chris@69: 
Chris@69: void ec_encode_bin(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _bits){
Chris@69:   opus_uint32 r;
Chris@69:   r=_this->rng>>_bits;
Chris@69:   if(_fl>0){
Chris@69:     _this->val+=_this->rng-IMUL32(r,((1U<<_bits)-_fl));
Chris@69:     _this->rng=IMUL32(r,(_fh-_fl));
Chris@69:   }
Chris@69:   else _this->rng-=IMUL32(r,((1U<<_bits)-_fh));
Chris@69:   ec_enc_normalize(_this);
Chris@69: }
Chris@69: 
Chris@69: /*The probability of having a "one" is 1/(1<<_logp).*/
Chris@69: void ec_enc_bit_logp(ec_enc *_this,int _val,unsigned _logp){
Chris@69:   opus_uint32 r;
Chris@69:   opus_uint32 s;
Chris@69:   opus_uint32 l;
Chris@69:   r=_this->rng;
Chris@69:   l=_this->val;
Chris@69:   s=r>>_logp;
Chris@69:   r-=s;
Chris@69:   if(_val)_this->val=l+r;
Chris@69:   _this->rng=_val?s:r;
Chris@69:   ec_enc_normalize(_this);
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_icdf(ec_enc *_this,int _s,const unsigned char *_icdf,unsigned _ftb){
Chris@69:   opus_uint32 r;
Chris@69:   r=_this->rng>>_ftb;
Chris@69:   if(_s>0){
Chris@69:     _this->val+=_this->rng-IMUL32(r,_icdf[_s-1]);
Chris@69:     _this->rng=IMUL32(r,_icdf[_s-1]-_icdf[_s]);
Chris@69:   }
Chris@69:   else _this->rng-=IMUL32(r,_icdf[_s]);
Chris@69:   ec_enc_normalize(_this);
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_uint(ec_enc *_this,opus_uint32 _fl,opus_uint32 _ft){
Chris@69:   unsigned  ft;
Chris@69:   unsigned  fl;
Chris@69:   int       ftb;
Chris@69:   /*In order to optimize EC_ILOG(), it is undefined for the value 0.*/
Chris@69:   celt_assert(_ft>1);
Chris@69:   _ft--;
Chris@69:   ftb=EC_ILOG(_ft);
Chris@69:   if(ftb>EC_UINT_BITS){
Chris@69:     ftb-=EC_UINT_BITS;
Chris@69:     ft=(_ft>>ftb)+1;
Chris@69:     fl=(unsigned)(_fl>>ftb);
Chris@69:     ec_encode(_this,fl,fl+1,ft);
Chris@69:     ec_enc_bits(_this,_fl&(((opus_uint32)1<<ftb)-1U),ftb);
Chris@69:   }
Chris@69:   else ec_encode(_this,_fl,_fl+1,_ft+1);
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_bits(ec_enc *_this,opus_uint32 _fl,unsigned _bits){
Chris@69:   ec_window window;
Chris@69:   int       used;
Chris@69:   window=_this->end_window;
Chris@69:   used=_this->nend_bits;
Chris@69:   celt_assert(_bits>0);
Chris@69:   if(used+_bits>EC_WINDOW_SIZE){
Chris@69:     do{
Chris@69:       _this->error|=ec_write_byte_at_end(_this,(unsigned)window&EC_SYM_MAX);
Chris@69:       window>>=EC_SYM_BITS;
Chris@69:       used-=EC_SYM_BITS;
Chris@69:     }
Chris@69:     while(used>=EC_SYM_BITS);
Chris@69:   }
Chris@69:   window|=(ec_window)_fl<<used;
Chris@69:   used+=_bits;
Chris@69:   _this->end_window=window;
Chris@69:   _this->nend_bits=used;
Chris@69:   _this->nbits_total+=_bits;
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_patch_initial_bits(ec_enc *_this,unsigned _val,unsigned _nbits){
Chris@69:   int      shift;
Chris@69:   unsigned mask;
Chris@69:   celt_assert(_nbits<=EC_SYM_BITS);
Chris@69:   shift=EC_SYM_BITS-_nbits;
Chris@69:   mask=((1<<_nbits)-1)<<shift;
Chris@69:   if(_this->offs>0){
Chris@69:     /*The first byte has been finalized.*/
Chris@69:     _this->buf[0]=(unsigned char)((_this->buf[0]&~mask)|_val<<shift);
Chris@69:   }
Chris@69:   else if(_this->rem>=0){
Chris@69:     /*The first byte is still awaiting carry propagation.*/
Chris@69:     _this->rem=(_this->rem&~mask)|_val<<shift;
Chris@69:   }
Chris@69:   else if(_this->rng<=(EC_CODE_TOP>>_nbits)){
Chris@69:     /*The renormalization loop has never been run.*/
Chris@69:     _this->val=(_this->val&~((opus_uint32)mask<<EC_CODE_SHIFT))|
Chris@69:      (opus_uint32)_val<<(EC_CODE_SHIFT+shift);
Chris@69:   }
Chris@69:   /*The encoder hasn't even encoded _nbits of data yet.*/
Chris@69:   else _this->error=-1;
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_shrink(ec_enc *_this,opus_uint32 _size){
Chris@69:   celt_assert(_this->offs+_this->end_offs<=_size);
Chris@69:   OPUS_MOVE(_this->buf+_size-_this->end_offs,
Chris@69:    _this->buf+_this->storage-_this->end_offs,_this->end_offs);
Chris@69:   _this->storage=_size;
Chris@69: }
Chris@69: 
Chris@69: void ec_enc_done(ec_enc *_this){
Chris@69:   ec_window   window;
Chris@69:   int         used;
Chris@69:   opus_uint32 msk;
Chris@69:   opus_uint32 end;
Chris@69:   int         l;
Chris@69:   /*We output the minimum number of bits that ensures that the symbols encoded
Chris@69:      thus far will be decoded correctly regardless of the bits that follow.*/
Chris@69:   l=EC_CODE_BITS-EC_ILOG(_this->rng);
Chris@69:   msk=(EC_CODE_TOP-1)>>l;
Chris@69:   end=(_this->val+msk)&~msk;
Chris@69:   if((end|msk)>=_this->val+_this->rng){
Chris@69:     l++;
Chris@69:     msk>>=1;
Chris@69:     end=(_this->val+msk)&~msk;
Chris@69:   }
Chris@69:   while(l>0){
Chris@69:     ec_enc_carry_out(_this,(int)(end>>EC_CODE_SHIFT));
Chris@69:     end=(end<<EC_SYM_BITS)&(EC_CODE_TOP-1);
Chris@69:     l-=EC_SYM_BITS;
Chris@69:   }
Chris@69:   /*If we have a buffered byte flush it into the output buffer.*/
Chris@69:   if(_this->rem>=0||_this->ext>0)ec_enc_carry_out(_this,0);
Chris@69:   /*If we have buffered extra bits, flush them as well.*/
Chris@69:   window=_this->end_window;
Chris@69:   used=_this->nend_bits;
Chris@69:   while(used>=EC_SYM_BITS){
Chris@69:     _this->error|=ec_write_byte_at_end(_this,(unsigned)window&EC_SYM_MAX);
Chris@69:     window>>=EC_SYM_BITS;
Chris@69:     used-=EC_SYM_BITS;
Chris@69:   }
Chris@69:   /*Clear any excess space and add any remaining extra bits to the last byte.*/
Chris@69:   if(!_this->error){
Chris@69:     OPUS_CLEAR(_this->buf+_this->offs,
Chris@69:      _this->storage-_this->offs-_this->end_offs);
Chris@69:     if(used>0){
Chris@69:       /*If there's no range coder data at all, give up.*/
Chris@69:       if(_this->end_offs>=_this->storage)_this->error=-1;
Chris@69:       else{
Chris@69:         l=-l;
Chris@69:         /*If we've busted, don't add too many extra bits to the last byte; it
Chris@69:            would corrupt the range coder data, and that's more important.*/
Chris@69:         if(_this->offs+_this->end_offs>=_this->storage&&l<used){
Chris@69:           window&=(1<<l)-1;
Chris@69:           _this->error=-1;
Chris@69:         }
Chris@69:         _this->buf[_this->storage-_this->end_offs-1]|=(unsigned char)window;
Chris@69:       }
Chris@69:     }
Chris@69:   }
Chris@69: }