Simple cleanups of AudioDecoder and AudioEncoder classes

webrtc/modules/audio_coding/codecs/g711/include/audio_decoder_pcm.h

 /*
  *  Copyright (c) 2015 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_CODECS_G711_INCLUDE_AUDIO_DECODER_PCM_H_
 #define WEBRTC_MODULES_AUDIO_CODING_CODECS_G711_INCLUDE_AUDIO_DECODER_PCM_H_
 
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
 
 namespace webrtc {
 
-class AudioDecoderPcmU : public AudioDecoder {
+class AudioDecoderPcmU final : public AudioDecoder {
  public:
-  AudioDecoderPcmU() {}
+  explicit AudioDecoderPcmU(size_t num_channels) : num_channels_(num_channels) {
+    RTC_DCHECK_GE(num_channels, 1u);
+  }
   void Reset() override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   size_t Channels() const override;
 
  protected:
   int DecodeInternal(const uint8_t* encoded,
                      size_t encoded_len,
                      int sample_rate_hz,
                      int16_t* decoded,
                      SpeechType* speech_type) override;
 
  private:
+  const size_t num_channels_;
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderPcmU);
 };
 
-class AudioDecoderPcmA : public AudioDecoder {
+class AudioDecoderPcmA final : public AudioDecoder {
  public:
-  AudioDecoderPcmA() {}
+  explicit AudioDecoderPcmA(size_t num_channels) : num_channels_(num_channels) {
+    RTC_DCHECK_GE(num_channels, 1u);
+  }
   void Reset() override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   size_t Channels() const override;
 
  protected:
   int DecodeInternal(const uint8_t* encoded,
                      size_t encoded_len,
                      int sample_rate_hz,
                      int16_t* decoded,
                      SpeechType* speech_type) override;
 
  private:
+  const size_t num_channels_;
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderPcmA);
 };
 
-class AudioDecoderPcmUMultiCh : public AudioDecoderPcmU {
- public:
-  explicit AudioDecoderPcmUMultiCh(size_t channels)
-      : AudioDecoderPcmU(), channels_(channels) {
-    RTC_DCHECK_GT(channels, 0u);
-  }
-  size_t Channels() const override;
+}  // namespace webrtc
 
- private:
-  const size_t channels_;
-  RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderPcmUMultiCh);
-};
-
-class AudioDecoderPcmAMultiCh : public AudioDecoderPcmA {
- public:
-  explicit AudioDecoderPcmAMultiCh(size_t channels)
-      : AudioDecoderPcmA(), channels_(channels) {
-    RTC_DCHECK_GT(channels, 0u);
-  }
-  size_t Channels() const override;
-
- private:
-  const size_t channels_;
-  RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderPcmAMultiCh);
-};
-
-}  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_G711_INCLUDE_AUDIO_DECODER_PCM_H_