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58 lines
1.7 KiB
58 lines
1.7 KiB
/*
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Copyright (C) 2000 Stefan Westerfeld
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stefan@space.twc.de
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with this library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#ifndef __HUFFMANLOOKUP_H
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#define __HUFFMANLOOKUP_H
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#include "mpegsound.h"
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/*
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* This class speeds up the huffman table decoding by largely replacing it
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* by a table lookup. It uses the fact that the huffman tables don't change,
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* and that given a byte of the bitstream, we can predict what the result
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* will be (without reading it bit by bit).
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*/
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class HuffmanLookup {
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private:
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long pattern, bits;
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int wgetbit();
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int wgetbits (int b);
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void huffmandecoder_1(const HUFFMANCODETABLE *h,int *x, int *y);
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ATTR_ALIGN(64) static struct decodeData {
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int x : 8;
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int y : 8;
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int skip : 16;
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} qdecode[32][256];
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public:
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HuffmanLookup();
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static int decode(int table, int pattern, int* x, int* y)
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{
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*x = qdecode[table][pattern].x;
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*y = qdecode[table][pattern].y;
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return qdecode[table][pattern].skip;
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}
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};
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#endif
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