libopenshot/src/Qt/VideoCacheThread.cpp

/**
 * @file
 * @brief Source file for VideoCacheThread class
 * @author Jonathan Thomas <jonathan@openshot.org>
 *
 * @ref License
 */

/* LICENSE
 *
 * Copyright (c) 2008-2019 OpenShot Studios, LLC
 * <http://www.openshotstudios.com/>. This file is part of
 * OpenShot Library (libopenshot), an open-source project dedicated to
 * delivering high quality video editing and animation solutions to the
 * world. For more information visit <http://www.openshot.org/>.
 *
 * OpenShot Library (libopenshot) is free software: you can redistribute it
 * and/or modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * OpenShot Library (libopenshot) is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with OpenShot Library. If not, see <http://www.gnu.org/licenses/>.
 */

#include "VideoCacheThread.h"
#include <algorithm>

#include <thread>    // for std::this_thread::sleep_for
#include <chrono>    // for std::chrono::milliseconds

namespace openshot
{
	// Constructor
	VideoCacheThread::VideoCacheThread()
	: Thread("video-cache"), speed(1), is_playing(false), position(1)
	, reader(NULL), max_frames(std::min(OPEN_MP_NUM_PROCESSORS * 8, 64)), current_display_frame(1)
    {
    }

    // Destructor
	VideoCacheThread::~VideoCacheThread()
    {
    }

    // Get the currently playing frame number (if any)
    int64_t VideoCacheThread::getCurrentFramePosition()
    {
    	if (frame)
    		return frame->number;
    	else
    		return 0;
    }

    // Set the currently playing frame number (if any)
    void VideoCacheThread::setCurrentFramePosition(int64_t current_frame_number)
    {
    	current_display_frame = current_frame_number;
    }

	// Seek the reader to a particular frame number
	void VideoCacheThread::Seek(int64_t new_position)
	{
		position = new_position;
	}

	// Play the video
	void VideoCacheThread::Play() {
		// Start playing
		is_playing = true;
	}

	// Stop the audio
	void VideoCacheThread::Stop() {
		// Stop playing
		is_playing = false;
	}

    // Start the thread
    void VideoCacheThread::run()
    {
        // Types for storing time durations in whole and fractional milliseconds
        using ms = std::chrono::milliseconds;
        using double_ms = std::chrono::duration<double, ms::period>;

        // Calculate on-screen time for a single frame in milliseconds
        const auto frame_duration = double_ms(1000.0 / reader->info.fps.ToDouble());

		while (!threadShouldExit() && is_playing) {

	    // Cache frames before the other threads need them
	    // Cache frames up to the max frames. Reset to current position
		// if cache gets too far away from display frame. Cache frames
		// even when player is paused (i.e. speed 0).
	    while ((position - current_display_frame) < max_frames)
	    {
	    	// Only cache up till the max_frames amount... then sleep
			try
			{
				if (reader) {
					ZmqLogger::Instance()->AppendDebugMethod("VideoCacheThread::run (cache frame)", "position", position, "current_display_frame", current_display_frame, "max_frames", max_frames, "needed_frames", (position - current_display_frame));

					// Force the frame to be generated
					if (reader->GetCache()->GetSmallestFrame()) {
						int64_t smallest_cached_frame = reader->GetCache()->GetSmallestFrame()->number;
						if (smallest_cached_frame > current_display_frame) {
							// Cache position has gotten too far away from current display frame.
							// Reset the position to the current display frame.
							position = current_display_frame;
						}
					}
					reader->GetFrame(position);
				}

			}
			catch (const OutOfBoundsFrame & e)
			{
				// Ignore out of bounds frame exceptions
			}

	    	// Increment frame number
			position++;
	    }

		// Sleep for 1 frame length
		std::this_thread::sleep_for(frame_duration);
	}

	return;
    }
}