| /* |
| * 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_FLOAT2HALF_H |
| #define AVCODEC_FLOAT2HALF_H |
| |
| #include <stdint.h> |
| |
| static void float2half_tables(uint16_t *basetable, uint8_t *shifttable) |
| { |
| for (int i = 0; i < 256; i++) { |
| int e = i - 127; |
| |
| if (e < -24) { // Very small numbers map to zero |
| basetable[i|0x000] = 0x0000; |
| basetable[i|0x100] = 0x8000; |
| shifttable[i|0x000] = 24; |
| shifttable[i|0x100] = 24; |
| } else if (e < -14) { // Small numbers map to denorms |
| basetable[i|0x000] = (0x0400>>(-e-14)); |
| basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000; |
| shifttable[i|0x000] = -e-1; |
| shifttable[i|0x100] = -e-1; |
| } else if (e <= 15) { // Normal numbers just lose precision |
| basetable[i|0x000] = ((e + 15) << 10); |
| basetable[i|0x100] = ((e + 15) << 10) | 0x8000; |
| shifttable[i|0x000] = 13; |
| shifttable[i|0x100] = 13; |
| } else if (e < 128) { // Large numbers map to Infinity |
| basetable[i|0x000] = 0x7C00; |
| basetable[i|0x100] = 0xFC00; |
| shifttable[i|0x000] = 24; |
| shifttable[i|0x100] = 24; |
| } else { // Infinity and NaN's stay Infinity and NaN's |
| basetable[i|0x000] = 0x7C00; |
| basetable[i|0x100] = 0xFC00; |
| shifttable[i|0x000] = 13; |
| shifttable[i|0x100] = 13; |
| } |
| } |
| } |
| |
| static uint16_t float2half(uint32_t f, uint16_t *basetable, uint8_t *shifttable) |
| { |
| uint16_t h; |
| |
| h = basetable[(f >> 23) & 0x1ff] + ((f & 0x007fffff) >> shifttable[(f >> 23) & 0x1ff]); |
| |
| return h; |
| } |
| |
| #endif /* AVCODEC_FLOAT2HALF_H */ |
