cad1593330
The codes here have the property that the long codes are to the left of the tree (each zero bit child node is by definition to the left of its one bit sibling); they also have the property that among codes of the same length, the symbol is ascending from left to right. These properties can be used to create the codes from the lengths in only two passes over the array of lengths (the current code uses one pass for each length, i.e. 32): First one counts how many nodes of each length there are. Then one calculates the range of codes of each length (possible because the codes are ordered by length in the tree). This enables one to calculate the actual codes with only one further traversal of the length array. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
84 lines
2.2 KiB
C
84 lines
2.2 KiB
C
/*
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* huffyuv codec for libavcodec
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*
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* Copyright (c) 2002-2014 Michael Niedermayer <michaelni@gmx.at>
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*
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* see http://www.pcisys.net/~melanson/codecs/huffyuv.txt for a description of
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* the algorithm used
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* huffyuv codec for libavcodec.
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*/
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#include <stdint.h>
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#include "libavutil/attributes.h"
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#include "libavutil/error.h"
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#include "libavutil/log.h"
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#include "libavutil/mem.h"
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#include "huffyuv.h"
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int ff_huffyuv_generate_bits_table(uint32_t *dst, const uint8_t *len_table, int n)
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{
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int lens[33] = { 0 };
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uint32_t codes[33];
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for (int i = 0; i < n; i++)
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lens[len_table[i]]++;
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codes[32] = 0;
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for (int i = FF_ARRAY_ELEMS(lens) - 1; i > 0; i--) {
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if ((lens[i] + codes[i]) & 1) {
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av_log(NULL, AV_LOG_ERROR, "Error generating huffman table\n");
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return -1;
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}
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codes[i - 1] = (lens[i] + codes[i]) >> 1;
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}
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for (int i = 0; i < n; i++) {
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if (len_table[i])
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dst[i] = codes[len_table[i]]++;
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}
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return 0;
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}
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av_cold int ff_huffyuv_alloc_temp(uint8_t *temp[3], uint16_t *temp16[3], int width)
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{
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int i;
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for (i=0; i<3; i++) {
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temp[i] = av_malloc(4 * width + 16);
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if (!temp[i])
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return AVERROR(ENOMEM);
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temp16[i] = (uint16_t*)temp[i];
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}
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return 0;
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}
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av_cold void ff_huffyuv_common_end(uint8_t *temp[3], uint16_t *temp16[3])
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{
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int i;
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for(i = 0; i < 3; i++) {
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av_freep(&temp[i]);
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temp16[i] = NULL;
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}
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}
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