chromium/third_party/webrtc/common_audio/signal_processing/resample_by_2.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 file contains the resampling by two functions.
 * The description header can be found in signal_processing_library.h
 *
 */

#include "common_audio/signal_processing/include/signal_processing_library.h"

#ifdef WEBRTC_ARCH_ARM_V7

// allpass filter coefficients.
static const uint32_t kResampleAllpass1[3] = {3284, 24441, 49528 << 15};
static const uint32_t kResampleAllpass2[3] =
  {12199, 37471 << 15, 60255 << 15};

// Multiply two 32-bit values and accumulate to another input value.
// Return: state + ((diff * tbl_value) >> 16)

static __inline int32_t MUL_ACCUM_1(int32_t tbl_value,
                                    int32_t diff,
                                    int32_t state) {
  int32_t result;
  __asm __volatile ("smlawb %0, %1, %2, %3": "=r"(result): "r"(diff),
                                   "r"(tbl_value), "r"(state));
  return result;
}

// Multiply two 32-bit values and accumulate to another input value.
// Return: Return: state + (((diff << 1) * tbl_value) >> 32)
//
// The reason to introduce this function is that, in case we can't use smlawb
// instruction (in MUL_ACCUM_1) due to input value range, we can still use 
// smmla to save some cycles.

static __inline int32_t MUL_ACCUM_2(int32_t tbl_value,
                                    int32_t diff,
                                    int32_t state) {
  int32_t result;
  __asm __volatile ("smmla %0, %1, %2, %3": "=r"(result): "r"(diff << 1),
                                  "r"(tbl_value), "r"(state));
  return result;
}

#else

// allpass filter coefficients.
static const uint16_t kResampleAllpass1[3] = …;
static const uint16_t kResampleAllpass2[3] = …;

// Multiply a 32-bit value with a 16-bit value and accumulate to another input:
#define MUL_ACCUM_1(a, b, c) …
#define MUL_ACCUM_2(a, b, c) …

#endif  // WEBRTC_ARCH_ARM_V7


// decimator
#if !defined(MIPS32_LE)
void WebRtcSpl_DownsampleBy2(const int16_t* in, size_t len,
                             int16_t* out, int32_t* filtState) { … }
#endif  // #if defined(MIPS32_LE)


void WebRtcSpl_UpsampleBy2(const int16_t* in, size_t len,
                           int16_t* out, int32_t* filtState) { … }