1 /*
2  *  Copyright (c) 2014 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_COMMON_AUDIO_FIR_FILTER_H_
12 #define WEBRTC_COMMON_AUDIO_FIR_FILTER_H_
13 
14 #include <string.h>
15 
16 namespace webrtc {
17 
18 // Finite Impulse Response filter using floating-point arithmetic.
19 class FIRFilter {
20  public:
21   // Creates a filter with the given coefficients. All initial state values will
22   // be zeros.
23   // The length of the chunks fed to the filter should never be greater than
24   // |max_input_length|. This is needed because, when vectorizing it is
25   // necessary to concatenate the input after the state, and resizing this array
26   // dynamically is expensive.
27   static FIRFilter* Create(const float* coefficients,
28                            size_t coefficients_length,
29                            size_t max_input_length);
30 
~FIRFilter()31   virtual ~FIRFilter() {}
32 
33   // Filters the |in| data supplied.
34   // |out| must be previously allocated and it must be at least of |length|.
35   virtual void Filter(const float* in, size_t length, float* out) = 0;
36 };
37 
38 }  // namespace webrtc
39 
40 #endif  // WEBRTC_COMMON_AUDIO_FIR_FILTER_H_
41