chromium/third_party/webrtc/common_audio/signal_processing/resample_by_2_internal.c

/*
 *  Copyright (c) 2011 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.
 */


/*
 * This header file contains some internal resampling functions.
 *
 */

#include "common_audio/signal_processing/resample_by_2_internal.h"
#include "rtc_base/sanitizer.h"

// allpass filter coefficients.
static const int16_t kResampleAllpass[2][3] = …;

//
//   decimator
// input:  int32_t (shifted 15 positions to the left, + offset 16384) OVERWRITTEN!
// output: int16_t (saturated) (of length len/2)
// state:  filter state array; length = 8

void RTC_NO_SANITIZE("signed-integer-overflow")  // bugs.webrtc.org/5486
WebRtcSpl_DownBy2IntToShort(int32_t *in, int32_t len, int16_t *out,
                            int32_t *state)
{ … }

//
//   decimator
// input:  int16_t
// output: int32_t (shifted 15 positions to the left, + offset 16384) (of length len/2)
// state:  filter state array; length = 8

void RTC_NO_SANITIZE("signed-integer-overflow")  // bugs.webrtc.org/5486
WebRtcSpl_DownBy2ShortToInt(const int16_t *in,
                            int32_t len,
                            int32_t *out,
                            int32_t *state)
{ … }

//
//   interpolator
// input:  int16_t
// output: int32_t (normalized, not saturated) (of length len*2)
// state:  filter state array; length = 8
void WebRtcSpl_UpBy2ShortToInt(const int16_t *in, int32_t len, int32_t *out,
                               int32_t *state)
{ … }

//
//   interpolator
// input:  int32_t (shifted 15 positions to the left, + offset 16384)
// output: int32_t (shifted 15 positions to the left, + offset 16384) (of length len*2)
// state:  filter state array; length = 8
void WebRtcSpl_UpBy2IntToInt(const int32_t *in, int32_t len, int32_t *out,
                             int32_t *state)
{ … }

//
//   interpolator
// input:  int32_t (shifted 15 positions to the left, + offset 16384)
// output: int16_t (saturated) (of length len*2)
// state:  filter state array; length = 8
void WebRtcSpl_UpBy2IntToShort(const int32_t *in, int32_t len, int16_t *out,
                               int32_t *state)
{ … }

//   lowpass filter
// input:  int16_t
// output: int32_t (normalized, not saturated)
// state:  filter state array; length = 8
void WebRtcSpl_LPBy2ShortToInt(const int16_t* in, int32_t len, int32_t* out,
                               int32_t* state)
{ … }

//   lowpass filter
// input:  int32_t (shifted 15 positions to the left, + offset 16384)
// output: int32_t (normalized, not saturated)
// state:  filter state array; length = 8
void RTC_NO_SANITIZE("signed-integer-overflow")  // bugs.webrtc.org/5486
WebRtcSpl_LPBy2IntToInt(const int32_t* in, int32_t len, int32_t* out,
                        int32_t* state)
{ … }