Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_
      12             : #define WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_
      13             : 
      14             : #include <cstdlib>
      15             : 
      16             : #include "webrtc/typedefs.h"
      17             : 
      18             : // Provides a set of static methods to perform dyadic decimations.
      19             : 
      20             : namespace webrtc {
      21             : 
      22             : // Returns the proper length of the output buffer that you should use for the
      23             : // given |in_length| and decimation |odd_sequence|.
      24             : // Return -1 on error.
      25           0 : inline size_t GetOutLengthToDyadicDecimate(size_t in_length,
      26             :                                            bool odd_sequence) {
      27           0 :   size_t out_length = in_length / 2;
      28             : 
      29           0 :   if (in_length % 2 == 1 && !odd_sequence) {
      30           0 :     ++out_length;
      31             :   }
      32             : 
      33           0 :   return out_length;
      34             : }
      35             : 
      36             : // Performs a dyadic decimation: removes every odd/even member of a sequence
      37             : // halving its overall length.
      38             : // Arguments:
      39             : //    in: array of |in_length|.
      40             : //    odd_sequence: If false, the odd members will be removed (1, 3, 5, ...);
      41             : //                  if true, the even members will be removed (0, 2, 4, ...).
      42             : //    out: array of |out_length|. |out_length| must be large enough to
      43             : //         hold the decimated output. The necessary length can be provided by
      44             : //         GetOutLengthToDyadicDecimate().
      45             : //         Must be previously allocated.
      46             : // Returns the number of output samples, -1 on error.
      47             : template<typename T>
      48           0 : static size_t DyadicDecimate(const T* in,
      49             :                              size_t in_length,
      50             :                              bool odd_sequence,
      51             :                              T* out,
      52             :                              size_t out_length) {
      53           0 :   size_t half_length = GetOutLengthToDyadicDecimate(in_length, odd_sequence);
      54             : 
      55           0 :   if (!in || !out || in_length <= 0 || out_length < half_length) {
      56           0 :     return 0;
      57             :   }
      58             : 
      59           0 :   size_t output_samples = 0;
      60           0 :   size_t index_adjustment = odd_sequence ? 1 : 0;
      61           0 :   for (output_samples = 0; output_samples < half_length; ++output_samples) {
      62           0 :     out[output_samples] = in[output_samples * 2 + index_adjustment];
      63             :   }
      64             : 
      65           0 :   return output_samples;
      66             : }
      67             : 
      68             : }  // namespace webrtc
      69             : 
      70             : #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_DYADIC_DECIMATOR_H_