Move AudioDecoder and related stuff to the api/ directory

BUG=webrtc:5805, webrtc:6725

Review-Url: https://codereview.webrtc.org/2668523004
Cr-Commit-Position: refs/heads/master@{#16534}

webrtc/api/audio_codecs/audio_format.h

@@ -0,0 +1,81 @@
+/*
+ *  Copyright (c) 2016 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_API_AUDIO_CODECS_AUDIO_FORMAT_H_
+#define WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_
+
+#include <map>
+#include <ostream>
+#include <string>
+#include <utility>
+
+namespace webrtc {
+
+// SDP specification for a single audio codec.
+// NOTE: This class is still under development and may change without notice.
+struct SdpAudioFormat {
+  using Parameters = std::map<std::string, std::string>;
+
+  SdpAudioFormat(const SdpAudioFormat&);
+  SdpAudioFormat(SdpAudioFormat&&);
+  SdpAudioFormat(const char* name, int clockrate_hz, int num_channels);
+  SdpAudioFormat(const std::string& name, int clockrate_hz, int num_channels);
+  SdpAudioFormat(const char* name,
+                 int clockrate_hz,
+                 int num_channels,
+                 const Parameters& param);
+  SdpAudioFormat(const std::string& name,
+                 int clockrate_hz,
+                 int num_channels,
+                 const Parameters& param);
+  ~SdpAudioFormat();
+
+  SdpAudioFormat& operator=(const SdpAudioFormat&);
+  SdpAudioFormat& operator=(SdpAudioFormat&&);
+
+  friend bool operator==(const SdpAudioFormat& a, const SdpAudioFormat& b);
+  friend bool operator!=(const SdpAudioFormat& a, const SdpAudioFormat& b) {
+    return !(a == b);
+  }
+
+  std::string name;
+  int clockrate_hz;
+  int num_channels;
+  Parameters parameters;
+};
+
+void swap(SdpAudioFormat& a, SdpAudioFormat& b);
+std::ostream& operator<<(std::ostream& os, const SdpAudioFormat& saf);
+
+// To avoid API breakage, and make the code clearer, AudioCodecSpec should not
+// be directly initializable with any flags indicating optional support. If it
+// were, these initializers would break any time a new flag was added. It's also
+// more difficult to understand:
+//   AudioCodecSpec spec{{"format", 8000, 1}, true, false, false, true, true};
+// than
+//   AudioCodecSpec spec({"format", 8000, 1});
+//   spec.allow_comfort_noise = true;
+//   spec.future_flag_b = true;
+//   spec.future_flag_c = true;
+struct AudioCodecSpec {
+  explicit AudioCodecSpec(const SdpAudioFormat& format);
+  explicit AudioCodecSpec(SdpAudioFormat&& format);
+  ~AudioCodecSpec() = default;
+
+  SdpAudioFormat format;
+  bool allow_comfort_noise = true;  // This codec can be used with an external
+                                    // comfort noise generator.
+  bool supports_network_adaption = false;  // This codec can adapt to varying
+                                           // network conditions.
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_