2 * Copyright (C) 2014 The Android Open Source Project
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 #include <audio_utils/minifloat.h>
20 #define EXPONENT_BITS 3
21 #define EXPONENT_MAX ((1 << EXPONENT_BITS) - 1)
22 #define EXCESS ((1 << EXPONENT_BITS) - 2)
24 #define MANTISSA_BITS 13
25 #define MANTISSA_MAX ((1 << MANTISSA_BITS) - 1)
26 #define HIDDEN_BIT (1 << MANTISSA_BITS)
27 #define ONE_FLOAT ((float) (1 << (MANTISSA_BITS + 1)))
29 #define MINIFLOAT_MAX ((EXPONENT_MAX << MANTISSA_BITS) | MANTISSA_MAX)
31 #if EXPONENT_BITS + MANTISSA_BITS != 16
32 #error EXPONENT_BITS and MANTISSA_BITS must sum to 16
35 gain_minifloat_t gain_from_float(float v)
37 if (isnan(v) || v <= 0.0f) {
44 float r = frexpf(v, &exp);
45 if ((exp += EXCESS) > EXPONENT_MAX) {
48 if (-exp >= MANTISSA_BITS) {
51 int mantissa = (int) (r * ONE_FLOAT);
52 return exp > 0 ? (exp << MANTISSA_BITS) | (mantissa & ~HIDDEN_BIT) :
53 (mantissa >> (1 - exp)) & MANTISSA_MAX;
56 float float_from_gain(gain_minifloat_t a)
58 int mantissa = a & MANTISSA_MAX;
59 int exponent = (a >> MANTISSA_BITS) & EXPONENT_MAX;
60 return ldexpf((exponent > 0 ? HIDDEN_BIT | mantissa : mantissa << 1) / ONE_FLOAT,