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* Copyright (c) 2012 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.
#include <stddef.h>
#include "rtc_base/constructormagic.h"
namespace webrtc {
// Forward declarations.
class AudioMultiVector;
class DecoderDatabase;
class SyncBuffer;
struct Packet;
// This class acts as an interface to the CNG generator.
class ComfortNoise {
enum ReturnCodes {
kOK = 0,
ComfortNoise(int fs_hz,
DecoderDatabase* decoder_database,
SyncBuffer* sync_buffer)
: fs_hz_(fs_hz),
overlap_length_(5 * fs_hz_ / 8000),
sync_buffer_(sync_buffer) {}
// Resets the state. Should be called before each new comfort noise period.
void Reset();
// Update the comfort noise generator with the parameters in |packet|.
int UpdateParameters(const Packet& packet);
// Generates |requested_length| samples of comfort noise and writes to
// |output|. If this is the first in call after Reset (or first after creating
// the object), it will also mix in comfort noise at the end of the
// SyncBuffer object provided in the constructor.
int Generate(size_t requested_length, AudioMultiVector* output);
// Returns the last error code that was produced by the comfort noise
// decoder. Returns 0 if no error has been encountered since the last reset.
int internal_error_code() { return internal_error_code_; }
int fs_hz_;
bool first_call_;
size_t overlap_length_;
DecoderDatabase* decoder_database_;
SyncBuffer* sync_buffer_;
int internal_error_code_;
} // namespace webrtc