| /* |
| * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #ifndef MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_ |
| #define MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_ |
| |
| #include <cstdlib> |
| |
| // Provides a set of static methods to perform dyadic decimations. |
| |
| namespace webrtc { |
| |
| // Returns the proper length of the output buffer that you should use for the |
| // given |in_length| and decimation |odd_sequence|. |
| // Return -1 on error. |
| inline size_t GetOutLengthToDyadicDecimate(size_t in_length, |
| bool odd_sequence) { |
| size_t out_length = in_length / 2; |
| |
| if (in_length % 2 == 1 && !odd_sequence) { |
| ++out_length; |
| } |
| |
| return out_length; |
| } |
| |
| // Performs a dyadic decimation: removes every odd/even member of a sequence |
| // halving its overall length. |
| // Arguments: |
| // in: array of |in_length|. |
| // odd_sequence: If false, the odd members will be removed (1, 3, 5, ...); |
| // if true, the even members will be removed (0, 2, 4, ...). |
| // out: array of |out_length|. |out_length| must be large enough to |
| // hold the decimated output. The necessary length can be provided by |
| // GetOutLengthToDyadicDecimate(). |
| // Must be previously allocated. |
| // Returns the number of output samples, -1 on error. |
| template <typename T> |
| static size_t DyadicDecimate(const T* in, |
| size_t in_length, |
| bool odd_sequence, |
| T* out, |
| size_t out_length) { |
| size_t half_length = GetOutLengthToDyadicDecimate(in_length, odd_sequence); |
| |
| if (!in || !out || in_length <= 0 || out_length < half_length) { |
| return 0; |
| } |
| |
| size_t output_samples = 0; |
| size_t index_adjustment = odd_sequence ? 1 : 0; |
| for (output_samples = 0; output_samples < half_length; ++output_samples) { |
| out[output_samples] = in[output_samples * 2 + index_adjustment]; |
| } |
| |
| return output_samples; |
| } |
| |
| } // namespace webrtc |
| |
| #endif // MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_ |