mirror of https://git.videolan.org/git/ffmpeg.git
68 lines
2.2 KiB
C
68 lines
2.2 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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#include "libavutil/half2float.h"
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#if !HAVE_FAST_FLOAT16
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static uint32_t convertmantissa(uint32_t i)
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{
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int32_t m = i << 13; // Zero pad mantissa bits
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int32_t e = 0; // Zero exponent
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while (!(m & 0x00800000)) { // While not normalized
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e -= 0x00800000; // Decrement exponent (1<<23)
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m <<= 1; // Shift mantissa
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}
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m &= ~0x00800000; // Clear leading 1 bit
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e += 0x38800000; // Adjust bias ((127-14)<<23)
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return m | e; // Return combined number
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}
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#endif
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void ff_init_half2float_tables(Half2FloatTables *t)
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{
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#if !HAVE_FAST_FLOAT16
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t->mantissatable[0] = 0;
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for (int i = 1; i < 1024; i++)
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t->mantissatable[i] = convertmantissa(i);
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for (int i = 1024; i < 2048; i++)
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t->mantissatable[i] = 0x38000000UL + ((i - 1024) << 13UL);
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for (int i = 2048; i < 3072; i++)
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t->mantissatable[i] = t->mantissatable[i - 1024] | 0x400000UL;
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t->mantissatable[2048] = t->mantissatable[1024];
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t->exponenttable[0] = 0;
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for (int i = 1; i < 31; i++)
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t->exponenttable[i] = i << 23;
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for (int i = 33; i < 63; i++)
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t->exponenttable[i] = 0x80000000UL + ((i - 32) << 23UL);
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t->exponenttable[31]= 0x47800000UL;
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t->exponenttable[32]= 0x80000000UL;
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t->exponenttable[63]= 0xC7800000UL;
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t->offsettable[0] = 0;
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for (int i = 1; i < 64; i++)
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t->offsettable[i] = 1024;
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t->offsettable[31] = 2048;
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t->offsettable[32] = 0;
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t->offsettable[63] = 2048;
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#endif
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}
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