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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* |
| 2 | * MQ-coder decoder |
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| 3 | * Copyright (c) 2007 Kamil Nowosad |
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| 4 | * |
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| 5 | * This file is part of FFmpeg. |
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| 6 | * |
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| 7 | * FFmpeg is free software; you can redistribute it and/or |
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| 8 | * modify it under the terms of the GNU Lesser General Public |
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| 9 | * License as published by the Free Software Foundation; either |
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| 10 | * version 2.1 of the License, or (at your option) any later version. |
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| 11 | * |
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| 12 | * FFmpeg is distributed in the hope that it will be useful, |
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 15 | * Lesser General Public License for more details. |
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| 16 | * |
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| 17 | * You should have received a copy of the GNU Lesser General Public |
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| 18 | * License along with FFmpeg; if not, write to the Free Software |
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| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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| 20 | */ |
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| 21 | |||
| 22 | /** |
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| 23 | * MQ-coder decoder |
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| 24 | * @file |
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| 25 | * @author Kamil Nowosad |
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| 26 | */ |
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| 27 | |||
| 28 | #include "mqc.h" |
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| 29 | |||
| 30 | static void bytein(MqcState *mqc) |
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| 31 | { |
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| 32 | if (*mqc->bp == 0xff) { |
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| 33 | if (*(mqc->bp + 1) > 0x8f) |
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| 34 | mqc->c++; |
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| 35 | else { |
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| 36 | mqc->bp++; |
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| 37 | mqc->c += 2 + 0xfe00 - (*mqc->bp << 9); |
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| 38 | } |
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| 39 | } else { |
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| 40 | mqc->bp++; |
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| 41 | mqc->c += 1 + 0xff00 - (*mqc->bp << 8); |
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| 42 | } |
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| 43 | } |
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| 44 | |||
| 45 | static int exchange(MqcState *mqc, uint8_t *cxstate, int lps) |
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| 46 | { |
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| 47 | int d; |
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| 48 | if ((mqc->a < ff_mqc_qe[*cxstate]) ^ (!lps)) { |
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| 49 | if (lps) |
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| 50 | mqc->a = ff_mqc_qe[*cxstate]; |
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| 51 | d = *cxstate & 1; |
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| 52 | *cxstate = ff_mqc_nmps[*cxstate]; |
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| 53 | } else { |
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| 54 | if (lps) |
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| 55 | mqc->a = ff_mqc_qe[*cxstate]; |
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| 56 | d = 1 - (*cxstate & 1); |
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| 57 | *cxstate = ff_mqc_nlps[*cxstate]; |
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| 58 | } |
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| 59 | // do RENORMD: see ISO/IEC 15444-1:2002 §C.3.3 |
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| 60 | do { |
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| 61 | if (!(mqc->c & 0xff)) { |
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| 62 | mqc->c -= 0x100; |
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| 63 | bytein(mqc); |
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| 64 | } |
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| 65 | mqc->a += mqc->a; |
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| 66 | mqc->c += mqc->c; |
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| 67 | } while (!(mqc->a & 0x8000)); |
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| 68 | return d; |
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| 69 | } |
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| 70 | |||
| 71 | void ff_mqc_initdec(MqcState *mqc, uint8_t *bp) |
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| 72 | { |
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| 73 | ff_mqc_init_contexts(mqc); |
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| 74 | mqc->bp = bp; |
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| 75 | mqc->c = (*mqc->bp ^ 0xff) << 16; |
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| 76 | bytein(mqc); |
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| 77 | mqc->c = mqc->c << 7; |
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| 78 | mqc->a = 0x8000; |
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| 79 | } |
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| 80 | |||
| 81 | int ff_mqc_decode(MqcState *mqc, uint8_t *cxstate) |
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| 82 | { |
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| 83 | mqc->a -= ff_mqc_qe[*cxstate]; |
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| 84 | if ((mqc->c >> 16) < mqc->a) { |
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| 85 | if (mqc->a & 0x8000) |
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| 86 | return *cxstate & 1; |
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| 87 | else |
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| 88 | return exchange(mqc, cxstate, 0); |
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| 89 | } else { |
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| 90 | mqc->c -= mqc->a << 16; |
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| 91 | return exchange(mqc, cxstate, 1); |
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| 92 | } |
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| 93 | } |