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diff --git a/webrtc/modules/audio_coding/codecs/audio_decoder.h b/webrtc/modules/audio_coding/codecs/audio_decoder.h
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+++ b/webrtc/modules/audio_coding/codecs/audio_decoder.h
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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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_INCLUDE_AUDIO_DECODER_H_
+#define WEBRTC_MODULES_AUDIO_CODING_NETEQ_INCLUDE_AUDIO_DECODER_H_
+
+#include <stdlib.h>  // NULL
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_coding/codecs/cng/include/webrtc_cng.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+// This is the interface class for decoders in NetEQ. Each codec type will have
+// and implementation of this class.
+class AudioDecoder {
+ public:
+  enum SpeechType {
+    kSpeech = 1,
+    kComfortNoise = 2
+  };
+
+  // Used by PacketDuration below. Save the value -1 for errors.
+  enum { kNotImplemented = -2 };
+
+  AudioDecoder() = default;
+  virtual ~AudioDecoder() = default;
+
+  // Decodes |encode_len| bytes from |encoded| and writes the result in
+  // |decoded|. The maximum bytes allowed to be written into |decoded| is
+  // |max_decoded_bytes|. Returns the total number of samples across all
+  // channels. If the decoder produced comfort noise, |speech_type|
+  // is set to kComfortNoise, otherwise it is kSpeech. The desired output
+  // sample rate is provided in |sample_rate_hz|, which must be valid for the
+  // codec at hand.
+  virtual int Decode(const uint8_t* encoded,
+                     size_t encoded_len,
+                     int sample_rate_hz,
+                     size_t max_decoded_bytes,
+                     int16_t* decoded,
+                     SpeechType* speech_type);
+
+  // Same as Decode(), but interfaces to the decoders redundant decode function.
+  // The default implementation simply calls the regular Decode() method.
+  virtual int DecodeRedundant(const uint8_t* encoded,
+                              size_t encoded_len,
+                              int sample_rate_hz,
+                              size_t max_decoded_bytes,
+                              int16_t* decoded,
+                              SpeechType* speech_type);
+
+  // Indicates if the decoder implements the DecodePlc method.
+  virtual bool HasDecodePlc() const;
+
+  // Calls the packet-loss concealment of the decoder to update the state after
+  // one or several lost packets. The caller has to make sure that the
+  // memory allocated in |decoded| should accommodate |num_frames| frames.
+  virtual size_t DecodePlc(size_t num_frames, int16_t* decoded);
+
+  // Resets the decoder state (empty buffers etc.).
+  virtual void Reset() = 0;
+
+  // Notifies the decoder of an incoming packet to NetEQ.
+  virtual int IncomingPacket(const uint8_t* payload,
+                             size_t payload_len,
+                             uint16_t rtp_sequence_number,
+                             uint32_t rtp_timestamp,
+                             uint32_t arrival_timestamp);
+
+  // Returns the last error code from the decoder.
+  virtual int ErrorCode();
+
+  // Returns the duration in samples-per-channel of the payload in |encoded|
+  // which is |encoded_len| bytes long. Returns kNotImplemented if no duration
+  // estimate is available, or -1 in case of an error.
+  virtual int PacketDuration(const uint8_t* encoded, size_t encoded_len) const;
+
+  // Returns the duration in samples-per-channel of the redandant payload in
+  // |encoded| which is |encoded_len| bytes long. Returns kNotImplemented if no
+  // duration estimate is available, or -1 in case of an error.
+  virtual int PacketDurationRedundant(const uint8_t* encoded,
+                                      size_t encoded_len) const;
+
+  // Detects whether a packet has forward error correction. The packet is
+  // comprised of the samples in |encoded| which is |encoded_len| bytes long.
+  // Returns true if the packet has FEC and false otherwise.
+  virtual bool PacketHasFec(const uint8_t* encoded, size_t encoded_len) const;
+
+  // If this is a CNG decoder, return the underlying CNG_dec_inst*. If this
+  // isn't a CNG decoder, don't call this method.
+  virtual CNG_dec_inst* CngDecoderInstance();
+
+  virtual size_t Channels() const = 0;
+
+ protected:
+  static SpeechType ConvertSpeechType(int16_t type);
+
+  virtual int DecodeInternal(const uint8_t* encoded,
+                             size_t encoded_len,
+                             int sample_rate_hz,
+                             int16_t* decoded,
+                             SpeechType* speech_type);
+
+  virtual int DecodeRedundantInternal(const uint8_t* encoded,
+                                      size_t encoded_len,
+                                      int sample_rate_hz,
+                                      int16_t* decoded,
+                                      SpeechType* speech_type);
+
+ private:
+  RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
+};
+
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_INCLUDE_AUDIO_DECODER_H_