diff options
Diffstat (limited to 'libavutil/float2half.c')
-rw-r--r-- | libavutil/float2half.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/libavutil/float2half.c b/libavutil/float2half.c new file mode 100644 index 0000000000..c79a3abfa1 --- /dev/null +++ b/libavutil/float2half.c @@ -0,0 +1,53 @@ +/* + * 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 + */ + +#include "libavutil/float2half.h" + +void ff_init_float2half_tables(Float2HalfTables *t) +{ + for (int i = 0; i < 256; i++) { + int e = i - 127; + + if (e < -24) { // Very small numbers map to zero + t->basetable[i|0x000] = 0x0000; + t->basetable[i|0x100] = 0x8000; + t->shifttable[i|0x000] = 24; + t->shifttable[i|0x100] = 24; + } else if (e < -14) { // Small numbers map to denorms + t->basetable[i|0x000] = (0x0400>>(-e-14)); + t->basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000; + t->shifttable[i|0x000] = -e-1; + t->shifttable[i|0x100] = -e-1; + } else if (e <= 15) { // Normal numbers just lose precision + t->basetable[i|0x000] = ((e + 15) << 10); + t->basetable[i|0x100] = ((e + 15) << 10) | 0x8000; + t->shifttable[i|0x000] = 13; + t->shifttable[i|0x100] = 13; + } else if (e < 128) { // Large numbers map to Infinity + t->basetable[i|0x000] = 0x7C00; + t->basetable[i|0x100] = 0xFC00; + t->shifttable[i|0x000] = 24; + t->shifttable[i|0x100] = 24; + } else { // Infinity and NaN's stay Infinity and NaN's + t->basetable[i|0x000] = 0x7C00; + t->basetable[i|0x100] = 0xFC00; + t->shifttable[i|0x000] = 13; + t->shifttable[i|0x100] = 13; + } + } +} |