mirror of https://bitbucket.org/ausocean/av.git
60 lines
2.0 KiB
C
60 lines
2.0 KiB
C
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/*
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DESCRIPTION
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parse_level_prefix.c contains a function that will parse the level_prefix
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when performaing CAVLC decoding; extracted from Emeric Grange's h264 decoder
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contained in MiniVideo (https://github.com/emericg/MiniVideo). This is used
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to generate input and output data for testing purposes.
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AUTHORS
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Emeric Grange <emeric.grange@gmail.com>
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Saxon A. Nelson-Milton <saxon@ausocean.org>
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LICENSE
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COPYRIGHT (C) 2018 Emeric Grange - All Rights Reserved
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This file is part of MiniVideo.
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MiniVideo is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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MiniVideo 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
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with MiniVideo. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "parse_level_prefix.h"
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#include "../helpers.h"
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/*!
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* \brief Parsing process for level_prefix.
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* \param *dc The current DecodingContext.
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* \return leadingZeroBits.
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*
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* From 'ITU-T H.264' recommendation:
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* 9.2.2.1 Parsing process for level_prefix
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*
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* The parsing process for this syntax element consists in reading the bits
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* starting at the current location in the bitstream up to and including the
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* first non-zero bit, and counting the number of leading bits that are equal to 0.
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*
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* level_prefix and level_suffix specify the value of a non-zero transform coefficient level.
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* The range of level_prefix and level_suffix is specified in subclause 9.2.2.
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*/
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int read_levelprefix(struct BitReader *br){
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int leadingZeroBits = -1;
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int b = 0;
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for (b = 0; !b; leadingZeroBits++){
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b = read_bits(br,1);
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if( br->err != 0 ){
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return -1;
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}
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}
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return leadingZeroBits;
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}
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