15f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// Copyright 2014 The Chromium Authors. All rights reserved. 25f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// found in the LICENSE file. 45f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 55f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)#ifndef MEDIA_BASE_TIME_SOURCE_H_ 65f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)#define MEDIA_BASE_TIME_SOURCE_H_ 75f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 85f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)#include "base/time/time.h" 95f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)#include "media/base/media_export.h" 105f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 115f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)namespace media { 125f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 135f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// A TimeSource is capable of providing the current media time. 145f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)class MEDIA_EXPORT TimeSource { 155f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) public: 165f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) TimeSource() {} 175f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual ~TimeSource() {} 185f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 195f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // Signal the time source to start ticking. It is expected that values from 205f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // CurrentMediaTime() will start increasing. 215f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual void StartTicking() = 0; 225f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 235f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // Signal the time source to stop ticking. It is expected that values from 245f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // CurrentMediaTime() will remain constant. 255f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual void StopTicking() = 0; 265f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 275f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // Updates the current playback rate. It is expected that values from 285f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // CurrentMediaTime() will eventually reflect the new playback rate (e.g., the 295f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // media time will advance at half speed if the rate was set to 0.5f). 305f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual void SetPlaybackRate(float playback_rate) = 0; 315f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 325f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // Sets the media time to start ticking from. Only valid to call while the 335f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // time source is not ticking. 345f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual void SetMediaTime(base::TimeDelta time) = 0; 355f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 365f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) // Returns the current media time. 371320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // 381320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // Values returned are intended for informational purposes, such as displaying 391320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // UI with the current minute and second count. While it is guaranteed values 401320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // will never go backwards, the frequency at which they update may be low. 415f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) virtual base::TimeDelta CurrentMediaTime() = 0; 421320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci 431320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // Returns the current media time for use with synchronizing video. 441320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // 451320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // Differences from CurrentMediaTime(): 461320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // - Values returned update at a much higher frequency (e.g., suitable for 471320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // playback of 60 FPS content). 481320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // - As a result, values may go slightly backwards depending on the 491320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // implementation (e.g., uses interpolation). 501320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // 511320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // TODO(scherkus): Replace with a method that returns wall clock time for a 521320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci // given media time for use with VideoFrameScheduler http://crbug.com/110814 531320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci virtual base::TimeDelta CurrentMediaTimeForSyncingVideo() = 0; 545f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)}; 555f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 565f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)} // namespace media 575f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 585f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)#endif // MEDIA_BASE_TIME_SOURCE_H_ 59