// 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 PACKAGER_MEDIA_BASE_AUDIO_TIMESTAMP_HELPER_H_ #define PACKAGER_MEDIA_BASE_AUDIO_TIMESTAMP_HELPER_H_ #include #include "packager/macros.h" namespace shaka { namespace media { // Generates timestamps for a sequence of audio sample frames. This class should // be used any place timestamps need to be calculated for a sequence of audio // samples. It helps avoid timestamps inaccuracies caused by rounding/truncation // in repeated sample count to timestamp conversions. // // The class is constructed with samples_per_second information so that it can // convert audio sample frame counts into timestamps. After the object is // constructed, SetBaseTimestamp() must be called to specify the starting // timestamp of the audio sequence. As audio samples are received, their frame // counts are added using AddFrames(). These frame counts are accumulated by // this class so GetTimestamp() can be used to determine the timestamp for the // samples that have been added. GetDuration() calculates the proper duration // values for samples added to the current timestamp. GetFramesToTarget() // determines the number of frames that need to be added/removed from the // accumulated frames to reach a target timestamp. class AudioTimestampHelper { public: explicit AudioTimestampHelper(int32_t timescale, uint32_t samples_per_second); // Sets the base timestamp to |base_timestamp| and the sets count to 0. void SetBaseTimestamp(int64_t base_timestamp); int64_t base_timestamp() const; int64_t frame_count() const { return frame_count_; } // Adds |frame_count| to the frame counter. // Note: SetBaseTimestamp() must be called with a value other than // kNoTimestamp() before this method can be called. void AddFrames(int64_t frame_count); // Get the current timestamp. This value is computed from the base_timestamp() // and the number of sample frames that have been added so far. int64_t GetTimestamp() const; // Gets the duration if |frame_count| frames were added to the current // timestamp reported by GetTimestamp(). This method ensures that // (GetTimestamp() + GetFrameDuration(n)) will equal the timestamp that // GetTimestamp() will return if AddFrames(n) is called. int64_t GetFrameDuration(int64_t frame_count) const; // Returns the number of frames needed to reach the target timestamp. // Note: |target| must be >= |base_timestamp_|. int64_t GetFramesToTarget(int64_t target) const; private: int64_t ComputeTimestamp(int64_t frame_count) const; double ticks_per_frame_; int64_t base_timestamp_; // Number of frames accumulated by AddFrames() calls. int64_t frame_count_; DISALLOW_IMPLICIT_CONSTRUCTORS(AudioTimestampHelper); }; } // namespace media } // namespace shaka #endif