ffmpeg/libavcodec/mqcenc.c

   1 /*
   2  * MQ-coder encoder
   3  * Copyright (c) 2007 Kamil Nowosad
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * MQ-coder encoder
  24  * @file
  25  * @author Kamil Nowosad
  26  */
  27
  28 #include "mqc.h"
  29
  30 static void byteout(MqcState *mqc)
  31 {
  32 retry:
  33     if (*mqc->bp == 0xff){
  34         mqc->bp++;
  35         *mqc->bp = mqc->c >> 20;
  36         mqc->c &= 0xfffff;
  37         mqc->ct = 7;
  38     } else if ((mqc->c & 0x8000000)){
  39         (*mqc->bp)++;
  40         mqc->c &= 0x7ffffff;
  41         goto retry;
  42     } else{
  43         mqc->bp++;
  44         *mqc->bp = mqc->c >> 19;
  45         mqc->c &= 0x7ffff;
  46         mqc->ct = 8;
  47     }
  48 }
  49
  50 static void renorme(MqcState *mqc)
  51 {
  52     do{
  53         mqc->a += mqc->a;
  54         mqc->c += mqc->c;
  55         if (!--mqc->ct)
  56             byteout(mqc);
  57     } while (!(mqc->a & 0x8000));
  58 }
  59
  60 static void setbits(MqcState *mqc)
  61 {
  62     int tmp = mqc->c + mqc->a;
  63     mqc->c |= 0xffff;
  64     if (mqc->c >= tmp)
  65         mqc->c -= 0x8000;
  66 }
  67
  68 void ff_mqc_initenc(MqcState *mqc, uint8_t *bp)
  69 {
  70     ff_mqc_init_contexts(mqc);
  71     mqc->a = 0x8000;
  72     mqc->c = 0;
  73     mqc->bp = bp-1;
  74     mqc->bpstart = bp;
  75     mqc->ct = 12 + (*mqc->bp == 0xff);
  76 }
  77
  78 void ff_mqc_encode(MqcState *mqc, uint8_t *cxstate, int d)
  79 {
  80     int qe;
  81
  82     qe = ff_mqc_qe[*cxstate];
  83     mqc->a -= qe;
  84     if ((*cxstate & 1) == d){
  85         if (!(mqc->a & 0x8000)){
  86             if (mqc->a < qe)
  87                 mqc->a = qe;
  88             else
  89                 mqc->c += qe;
  90             *cxstate = ff_mqc_nmps[*cxstate];
  91             renorme(mqc);
  92         } else
  93             mqc->c += qe;
  94     } else{
  95         if (mqc->a < qe)
  96             mqc->c += qe;
  97         else
  98             mqc->a = qe;
  99         *cxstate = ff_mqc_nlps[*cxstate];
 100         renorme(mqc);
 101     }
 102 }
 103
 104 int ff_mqc_length(MqcState *mqc)
 105 {
 106     return mqc->bp - mqc->bpstart;
 107 }
 108
 109 int ff_mqc_flush(MqcState *mqc)
 110 {
 111     setbits(mqc);
 112     mqc->c = mqc->c << mqc->ct;
 113     byteout(mqc);
 114     mqc->c = mqc->c << mqc->ct;
 115     byteout(mqc);
 116     if (*mqc->bp != 0xff)
 117         mqc->bp++;
 118     return mqc->bp - mqc->bpstart;
 119 }