1 /****************************************************************************** 2 * 3 * Copyright 2021 Google, Inc. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ******************************************************************************/ 18 19 /** 20 * LC3 - Compute LD-MDCT (Low Delay Modified Discret Cosinus Transform) 21 * 22 * Reference : Low Complexity Communication Codec (LC3) 23 * Bluetooth Specification v1.0 24 */ 25 26 #ifndef __LC3_MDCT_H 27 #define __LC3_MDCT_H 28 29 #include "common.h" 30 31 32 /** 33 * Forward MDCT transformation 34 * dt, sr Duration and samplerate (size of the transform) 35 * sr_dst Samplerate destination, scale transforam accordingly 36 * x [-nd..-1] Previous, [0..ns-1] Current samples 37 * y Output `ns` frequency coefficients 38 * 39 * The number of previous samples `nd` accessed on `x` is : 40 * nd: `ns` * 23/30 for 7.5ms frame duration 41 * nd: `ns` * 5/ 8 for 10ms frame duration 42 */ 43 void lc3_mdct_forward(enum lc3_dt dt, enum lc3_srate sr, 44 enum lc3_srate sr_dst, const float *x, float *y); 45 46 /** 47 * Inverse MDCT transformation 48 * dt, sr Duration and samplerate (size of the transform) 49 * sr_src Samplerate source, scale transforam accordingly 50 * x, d Frequency coefficients and delayed buffer 51 * y, d Output `ns` samples and `nd` delayed ones 52 * 53 * `x` and `y` can be the same buffer 54 */ 55 void lc3_mdct_inverse(enum lc3_dt dt, enum lc3_srate sr, 56 enum lc3_srate sr_src, const float *x, float *d, float *y); 57 58 59 #endif /* __LC3_MDCT_H */ 60