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https://github.com/FFmpeg/FFmpeg.git
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68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
/*
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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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#ifndef AVCODEC_FLOAT2HALF_H
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#define AVCODEC_FLOAT2HALF_H
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#include <stdint.h>
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static void float2half_tables(uint16_t *basetable, uint8_t *shifttable)
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{
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for (int i = 0; i < 256; i++) {
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int e = i - 127;
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if (e < -24) { // Very small numbers map to zero
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basetable[i|0x000] = 0x0000;
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basetable[i|0x100] = 0x8000;
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shifttable[i|0x000] = 24;
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shifttable[i|0x100] = 24;
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} else if (e < -14) { // Small numbers map to denorms
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basetable[i|0x000] = (0x0400>>(-e-14));
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basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000;
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shifttable[i|0x000] = -e-1;
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shifttable[i|0x100] = -e-1;
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} else if (e <= 15) { // Normal numbers just lose precision
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basetable[i|0x000] = ((e + 15) << 10);
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basetable[i|0x100] = ((e + 15) << 10) | 0x8000;
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shifttable[i|0x000] = 13;
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shifttable[i|0x100] = 13;
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} else if (e < 128) { // Large numbers map to Infinity
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basetable[i|0x000] = 0x7C00;
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basetable[i|0x100] = 0xFC00;
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shifttable[i|0x000] = 24;
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shifttable[i|0x100] = 24;
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} else { // Infinity and NaN's stay Infinity and NaN's
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basetable[i|0x000] = 0x7C00;
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basetable[i|0x100] = 0xFC00;
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shifttable[i|0x000] = 13;
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shifttable[i|0x100] = 13;
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}
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}
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}
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static uint16_t float2half(uint32_t f, uint16_t *basetable, uint8_t *shifttable)
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{
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uint16_t h;
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h = basetable[(f >> 23) & 0x1ff] + ((f & 0x007fffff) >> shifttable[(f >> 23) & 0x1ff]);
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return h;
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}
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#endif /* AVCODEC_FLOAT2HALF_H */
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