Add the option of compressing speech input audio using FLAC.

chrome/browser/speech/audio_encoder.h

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_SPEECH_AUDIO_ENCODER_H_
+#define CHROME_BROWSER_SPEECH_AUDIO_ENCODER_H_
+
+#include <list>
+#include <string>
+
+#include "base/basictypes.h"
+
+namespace speech_input {
+
+// Provides a simple interface to encode raw audio using the various speech
+// codecs.
+class AudioEncoder {
+ public:
+  enum Codec {
+    CODEC_FLAC,
+    CODEC_SPEEX,
+  };
+
+  static AudioEncoder* Create(Codec codec,
+                              int sampling_rate,
+                              int bits_per_sample);
+
+  virtual ~AudioEncoder();
+
+  // Encodes each frame of raw audio in |samples| to the internal buffer. Use
+  // |GetEncodedData| to read the result after this call or when recording
+  // completes.
+  virtual void Encode(const short* samples, int num_samples) = 0;
+
+  // Finish encoding and flush any pending encoded bits out.
+  virtual void Flush() = 0;
+
+  // Copies the encoded audio to the given string. Returns true if the output
+  // is not empty.
+  bool GetEncodedData(std::string* encoded_data);
+
+  const std::string& mime_type() { return mime_type_; }
+
+ protected:
+  AudioEncoder(const std::string& mime_type);
+
+  void AppendToBuffer(std::string* item);
+
+ private:
+  // Buffer holding the recorded audio. Owns the strings inside the list.
+  typedef std::list<std::string*> AudioBufferQueue;
+  AudioBufferQueue audio_buffers_;
+  std::string mime_type_;
+  DISALLOW_COPY_AND_ASSIGN(AudioEncoder);
+};
+
+}  // namespace speech_input
+
+#endif  // CHROME_BROWSER_SPEECH_AUDIO_ENCODER_H_