diff options
author | Paul B Mahol <onemda@gmail.com> | 2021-02-28 12:44:25 +0100 |
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committer | Paul B Mahol <onemda@gmail.com> | 2021-03-02 20:53:04 +0100 |
commit | 6cc3ba4be64caa9c402740cd0b2c9b91bbb2cfe8 (patch) | |
tree | 51871168eecbc3cf1f1cfce6d8470d82e627a71b /libavcodec/half2float.h | |
parent | cf2f8dcc6af440ef1be4da35331caa7d719f1230 (diff) |
avcodec/exr: add lut oriented half to float conversion code
Diffstat (limited to 'libavcodec/half2float.h')
-rw-r--r-- | libavcodec/half2float.h | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/libavcodec/half2float.h b/libavcodec/half2float.h new file mode 100644 index 0000000000..9cff12a309 --- /dev/null +++ b/libavcodec/half2float.h @@ -0,0 +1,74 @@ +/* + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef AVCODEC_HALF2FLOAT_H +#define AVCODEC_HALF2FLOAT_H + +#include <stdint.h> + +static uint32_t convertmantissa(uint32_t i) +{ + uint32_t m = i << 13; // Zero pad mantissa bits + uint32_t e = 0; // Zero exponent + + while (!(m & 0x00800000UL)){ // While not normalized + e -= 0x00800000UL; // Decrement exponent (1<<23) + m <<= 1; // Shift mantissa + } + + m &= ~0x00800000UL; // Clear leading 1 bit + e += 0x38800000UL; // Adjust bias ((127-14)<<23) + + return m | e; // Return combined number +} + +static void half2float_table(uint32_t *mantissatable, uint32_t *exponenttable, + uint16_t *offsettable) +{ + mantissatable[0] = 0; + for (int i = 1; i < 1024; i++) + mantissatable[i] = convertmantissa(i); + for (int i = 1024; i < 2048; i++) + mantissatable[i] = 0x38000000UL + ((i - 1024) << 13UL); + + exponenttable[0] = 0; + for (int i = 1; i < 31; i++) + exponenttable[i] = i << 23; + for (int i = 33; i < 63; i++) + exponenttable[i] = 0x80000000UL + ((i - 32) << 23UL); + exponenttable[31]= 0x47800000UL; + exponenttable[32]= 0x80000000UL; + exponenttable[63]= 0xC7800000UL; + + offsettable[0] = 0; + for (int i = 1; i < 64; i++) + offsettable[i] = 1024; + offsettable[32] = 0; +} + +static uint32_t half2float(uint16_t h, uint32_t *mantissatable, uint32_t *exponenttable, + uint16_t *offsettable) +{ + uint32_t f; + + f = mantissatable[offsettable[h >> 10] + (h & 0x3ff)] + exponenttable[h >> 10]; + + return f; +} + +#endif /* AVCODEC_HALF2FLOAT_H */ |