talk/sound/soundoutputstreaminterface.h

/*
 * libjingle
 * Copyright 2004--2010, Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 */

#ifndef TALK_SOUND_SOUNDOUTPUTSTREAMINTERFACE_H_
#define TALK_SOUND_SOUNDOUTPUTSTREAMINTERFACE_H_

#include "talk/base/constructormagic.h"
#include "talk/base/sigslot.h"

namespace cricket {

// Interface for outputting a stream to a playback device.
// Semantics and thread-safety of EnableBufferMonitoring()/
// DisableBufferMonitoring() are the same as for talk_base::Worker.
class SoundOutputStreamInterface {
 public:
  virtual ~SoundOutputStreamInterface() {}

  // Enables monitoring the available buffer space on the current thread.
  virtual bool EnableBufferMonitoring() = 0;
  // Disables the monitoring.
  virtual bool DisableBufferMonitoring() = 0;

  // Write the given samples to the devices. If currently monitoring then this
  // may only be called from the monitoring thread.
  virtual bool WriteSamples(const void *sample_data,
                            size_t size) = 0;

  // Retrieves the current output volume for this stream. Nominal range is
  // defined by SoundSystemInterface::k(Max|Min)Volume, but values exceeding the
  // max may be possible in some implementations. This call retrieves the actual
  // volume currently in use by the OS, not a cached value from a previous
  // (Get|Set)Volume() call.
  virtual bool GetVolume(int *volume) = 0;

  // Changes the output volume for this stream. Nominal range is defined by
  // SoundSystemInterface::k(Max|Min)Volume. The effect of exceeding kMaxVolume
  // is implementation-defined.
  virtual bool SetVolume(int volume) = 0;

  // Closes this stream object. If currently monitoring then this may only be
  // called from the monitoring thread.
  virtual bool Close() = 0;

  // Get the latency of the stream.
  virtual int LatencyUsecs() = 0;

  // Notifies the producer of the available buffer space for writes.
  // It fires continuously as long as the space is greater than zero.
  // The first parameter is the amount of buffer space available for data to
  // be written (i.e., the maximum amount of data that can be written right now
  // with WriteSamples() without blocking).
  // The 2nd parameter is the stream that is issuing the callback.
  sigslot::signal2<size_t, SoundOutputStreamInterface *> SignalBufferSpace;

 protected:
  SoundOutputStreamInterface() {}

 private:
  DISALLOW_COPY_AND_ASSIGN(SoundOutputStreamInterface);
};

}  // namespace cricket

#endif  // TALK_SOUND_SOUNDOUTPUTSTREAMINTERFACE_H_