media/audio/linux: Add CrasInputStream.

media/audio/linux/cras_input.h

+// Copyright (c) 2012 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 MEDIA_AUDIO_LINUX_CRAS_INPUT_H_
+#define MEDIA_AUDIO_LINUX_CRAS_INPUT_H_
+
+#include <cras_client.h>
+
+#include <string>
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time.h"
+#include "media/audio/audio_input_stream_impl.h"
+#include "media/audio/audio_io.h"
+#include "media/audio/audio_parameters.h"
+
+namespace media {
+
+class AudioManagerLinux;
+
+// Provides an input stream for audio capture based on CRAS, the ChromeOS Audio
+// Server.  This object is not thread safe and all methods should be invoked in
+// the thread that created the object.
+class CrasInputStream : public AudioInputStreamImpl {
+ public:
+  // The ctor takes all the usual parameters, plus |manager| which is the
+  // audio manager who is creating this object.
+  CrasInputStream(const AudioParameters& params, AudioManagerLinux* manager);
+
+  // The dtor is typically called by the AudioManager only and it is usually
+  // triggered by calling AudioOutputStream::Close().
+  virtual ~CrasInputStream();
+
+  // Implementation of AudioInputStream.
+  virtual bool Open() OVERRIDE;
+  virtual void Start(AudioInputCallback* callback) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void Close() OVERRIDE;
+  virtual double GetMaxVolume() OVERRIDE;
+  virtual void SetVolume(double volume) OVERRIDE;
+  virtual double GetVolume() OVERRIDE;
+
+ private:
+  // Handles requests to get samples from the provided buffer.  This will be
+  // called by the audio server when it has samples ready.
+  static int SamplesReady(cras_client* client,
+                          cras_stream_id_t stream_id,
+                          uint8* samples,
+                          size_t frames,
+                          const timespec* sample_ts,
+                          void* arg);
+
+  // Handles notificaiton that there was an error with the playback stream.
+  static int StreamError(cras_client* client,
+                         cras_stream_id_t stream_id,
+                         int err,
+                         void* arg);
+
+  // Reads one or more buffers of audio from the device, passes on to the
+  // registered callback. Called from SamplesReady().
+  void ReadAudio(size_t frames, uint8* buffer, const timespec* sample_ts);
+
+  // Deals with an error that occured in the stream.  Called from StreamError().
+  void NotifyStreamError(int err);
+
+  // Convert from dB * 100 to a volume ratio.
+  double GetVolumeRatioFromDecibels(double dB) const;
+
+  // Convert from a volume ratio to dB.
+  double GetDecibelsFromVolumeRatio(double volume_ratio) const;
+
+  // Non-refcounted pointer back to the audio manager.
+  // The AudioManager indirectly holds on to stream objects, so we don't
+  // want circular references.  Additionally, stream objects live on the audio
+  // thread, which is owned by the audio manager and we don't want to addref
+  // the manager from that thread.
+  AudioManagerLinux* audio_manager_;
+
+  // Size of frame in bytes.
+  uint32 bytes_per_frame_;
+
+  // Callback to pass audio samples too, valid while recording.
+  AudioInputCallback* callback_;
+
+  // The client used to communicate with the audio server.
+  cras_client* client_;
+
+  // PCM parameters for the stream.
+  AudioParameters params_;
+
+  // True if the stream has been started.
+  bool started_;
+
+  // ID of the playing stream.
+  cras_stream_id_t stream_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(CrasInputStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_LINUX_ALSA_INPUT_H_