media/libopus/celt/entcode.c@b8a032363ba2 (annotated)
media/libopus/celt/entcode.c
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | /* Copyright (c) 2001-2011 Timothy B. Terriberry |
| michael@0 | 2 | */ |
| michael@0 | 3 | /* |
| michael@0 | 4 | Redistribution and use in source and binary forms, with or without |
| michael@0 | 5 | modification, are permitted provided that the following conditions |
| michael@0 | 6 | are met: |
| michael@0 | 7 | |
| michael@0 | 8 | - Redistributions of source code must retain the above copyright |
| michael@0 | 9 | notice, this list of conditions and the following disclaimer. |
| michael@0 | 10 | |
| michael@0 | 11 | - Redistributions in binary form must reproduce the above copyright |
| michael@0 | 12 | notice, this list of conditions and the following disclaimer in the |
| michael@0 | 13 | documentation and/or other materials provided with the distribution. |
| michael@0 | 14 | |
| michael@0 | 15 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| michael@0 | 16 | ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| michael@0 | 17 | LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| michael@0 | 18 | A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER |
| michael@0 | 19 | OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| michael@0 | 20 | EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| michael@0 | 21 | PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| michael@0 | 22 | PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
| michael@0 | 23 | LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| michael@0 | 24 | NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| michael@0 | 25 | SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| michael@0 | 26 | */ |
| michael@0 | 27 | |
| michael@0 | 28 | #ifdef HAVE_CONFIG_H |
| michael@0 | 29 | #include "config.h" |
| michael@0 | 30 | #endif |
| michael@0 | 31 | |
| michael@0 | 32 | #include "entcode.h" |
| michael@0 | 33 | #include "arch.h" |
| michael@0 | 34 | |
| michael@0 | 35 | #if !defined(EC_CLZ) |
| michael@0 | 36 | /*This is a fallback for systems where we don't know how to access |
| michael@0 | 37 | a BSR or CLZ instruction (see ecintrin.h). |
| michael@0 | 38 | If you are optimizing Opus on a new platform and it has a native CLZ or |
| michael@0 | 39 | BZR (e.g. cell, MIPS, x86, etc) then making it available to Opus will be |
| michael@0 | 40 | an easy performance win.*/ |
| michael@0 | 41 | int ec_ilog(opus_uint32 _v){ |
| michael@0 | 42 | /*On a Pentium M, this branchless version tested as the fastest on |
| michael@0 | 43 | 1,000,000,000 random 32-bit integers, edging out a similar version with |
| michael@0 | 44 | branches, and a 256-entry LUT version.*/ |
| michael@0 | 45 | int ret; |
| michael@0 | 46 | int m; |
| michael@0 | 47 | ret=!!_v; |
| michael@0 | 48 | m=!!(_v&0xFFFF0000)<<4; |
| michael@0 | 49 | _v>>=m; |
| michael@0 | 50 | ret|=m; |
| michael@0 | 51 | m=!!(_v&0xFF00)<<3; |
| michael@0 | 52 | _v>>=m; |
| michael@0 | 53 | ret|=m; |
| michael@0 | 54 | m=!!(_v&0xF0)<<2; |
| michael@0 | 55 | _v>>=m; |
| michael@0 | 56 | ret|=m; |
| michael@0 | 57 | m=!!(_v&0xC)<<1; |
| michael@0 | 58 | _v>>=m; |
| michael@0 | 59 | ret|=m; |
| michael@0 | 60 | ret+=!!(_v&0x2); |
| michael@0 | 61 | return ret; |
| michael@0 | 62 | } |
| michael@0 | 63 | #endif |
| michael@0 | 64 | |
| michael@0 | 65 | opus_uint32 ec_tell_frac(ec_ctx *_this){ |
| michael@0 | 66 | opus_uint32 nbits; |
| michael@0 | 67 | opus_uint32 r; |
| michael@0 | 68 | int l; |
| michael@0 | 69 | int i; |
| michael@0 | 70 | /*To handle the non-integral number of bits still left in the encoder/decoder |
| michael@0 | 71 | state, we compute the worst-case number of bits of val that must be |
| michael@0 | 72 | encoded to ensure that the value is inside the range for any possible |
| michael@0 | 73 | subsequent bits. |
| michael@0 | 74 | The computation here is independent of val itself (the decoder does not |
| michael@0 | 75 | even track that value), even though the real number of bits used after |
| michael@0 | 76 | ec_enc_done() may be 1 smaller if rng is a power of two and the |
| michael@0 | 77 | corresponding trailing bits of val are all zeros. |
| michael@0 | 78 | If we did try to track that special case, then coding a value with a |
| michael@0 | 79 | probability of 1/(1<<n) might sometimes appear to use more than n bits. |
| michael@0 | 80 | This may help explain the surprising result that a newly initialized |
| michael@0 | 81 | encoder or decoder claims to have used 1 bit.*/ |
| michael@0 | 82 | nbits=_this->nbits_total<<BITRES; |
| michael@0 | 83 | l=EC_ILOG(_this->rng); |
| michael@0 | 84 | r=_this->rng>>(l-16); |
| michael@0 | 85 | for(i=BITRES;i-->0;){ |
| michael@0 | 86 | int b; |
| michael@0 | 87 | r=r*r>>15; |
| michael@0 | 88 | b=(int)(r>>16); |
| michael@0 | 89 | l=l<<1|b; |
| michael@0 | 90 | r>>=b; |
| michael@0 | 91 | } |
| michael@0 | 92 | return nbits-l; |
| michael@0 | 93 | } |
