| /* Copyright 2019 The TensorFlow Authors. All Rights Reserved. |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| ==============================================================================*/ |
| |
| #ifndef SIGNAL_SRC_FILTER_BANK_H_ |
| #define SIGNAL_SRC_FILTER_BANK_H_ |
| |
| #include <stdint.h> |
| |
| namespace tflite { |
| namespace tflm_signal { |
| // TODO(b/286250473): remove namespace once de-duped libraries above |
| |
| struct FilterbankConfig { |
| // Number of filterbank channels |
| int32_t num_channels; |
| |
| // Each of the following three arrays is of size num_channels + 1 |
| // An extra channel is needed for scratch. See implementation of |
| // FilterbankAccumulateChannels() for more details |
| |
| // For each channel, the index in the input (spectrum) where its band starts |
| const int16_t* channel_frequency_starts; |
| // For each channel, the index in the weights/unweights arrays where |
| // it filter weights start |
| const int16_t* channel_weight_starts; |
| // For each channel, the number of bins in the input (spectrum) that span |
| // its band |
| const int16_t* channel_widths; |
| |
| // The weights array holds the triangular filter weights of all the filters |
| // in the bank. The output of each filter in the bank is caluclated by |
| // multiplying the elements in the input spectrum that are in its band |
| // (see above: channel_frequency_starts, channel_widths) by the filter weights |
| // then accumulating. Each element in the unweights array holds the 1 minus |
| // corresponding elements in the weights array and is used to make this |
| // operation more efficient. For more details, see documnetation in |
| // FilterbankAccumulateChannels() |
| const int16_t* weights; |
| const int16_t* unweights; |
| int32_t output_scale; |
| |
| int32_t input_correction_bits; |
| }; |
| |
| // Accumulate the energy spectrum bins in `input` into filter bank channels |
| // contained in `output`. |
| // * `input` - Spectral energy array |
| // * `output` - of size `config.num_channels` + 1. |
| // Elements [1:num_channels] contain the filter bank channels. |
| // Element 0 is used as scratch and should be ignored |
| void FilterbankAccumulateChannels(const FilterbankConfig* config, |
| const uint32_t* input, uint64_t* output); |
| |
| } // namespace tflm_signal |
| } // namespace tflite |
| |
| #endif // SIGNAL_SRC_FILTER_BANK_H_ |