降低MIDI播放线程上的CPU

Question

下面的函数在分离的std :: thread上运行。 代码本身是使用JUCE API（因此Array <>对象和MidiMessage）编写的。

 void triggerMidiMessages(Array<Array<MidiMessage>> messageBundle) 
{
    //for each group of messages (bar) within the bundle
    for(int bar = 0; bar < messageBundle.size(); bar ++)
    {   
        //store our message from the bundle for playback
        Array<MidiMessage> messages;
        messages.clear();
        messages = messageBundle[bar];

        //intialise start time
        double timestart = Time::getMillisecondCounterHiRes();

        //for each midi inside a single "gene"
        for(int i = 0; i <= messages.size();)
        {
            double elapsedTime = Time::getMillisecondCounterHiRes() - timestart;

            //output message whens appropriate
            if(elapsedTime > messages[i].getTimeStamp())
            {
                //output this message
                masterMidiOutput->sendMessageNow(messages[i]);

                //increment through the array
                i++;
            }
        }
    }
}

我需要实时输出Midi消息，但不必经历循环条件，以免CPU过热。

有任何想法吗？ 我对如何以不需要使用计时器进行持续检查的顺序播放消息感到困惑。

提前致谢。

// ================================================ =====================更新尝试使线程休眠...

void triggerMidiMessages(Array<Array<MidiMessage>> messageBundle)
{
    //for each group of messages (bar) within a bundle
    for(int bar = 0; bar < messageBundle.size(); bar ++)
    {   
        //store our message from the bundle for playback
        Array<MidiMessage> messages;
        messages.clear();
        messages = messageBundle[bar];
        }

        //intialise start time
        double previousTimeStamp = 0;

        //for each midi inside a single "gene"
        for(int i = 0; i <= messages.size();)
        {
            //fire off all note on messages
            while(messages[i].isNoteOn())
            {
                masterMidiOutput->sendMessageNow(messages[i]);
                i++; //increment to the next
            }

            //fire off all note off messages
            while(!messages[i].isNoteOn())
            {
                masterMidiOutput->sendMessageNow(messages[i]);
                 i++; // do the next one

                //if the next message is back to a note on command
                if(messages[i+1].isNoteOn() == true)
                {
                    //sleep for x amount of time
                    int sleepTime = messages[i].getTimeStamp() - previousTimeStamp;
                    std::this_thread::sleep_for(std::chrono::milliseconds(sleepTime));
                    previousTimeStamp = messages[i].getTimeStamp();
                }
            }

        }
    }
}

Answer 1

要停止线程中的构建，最好打开和关闭计时器对象并逐个触发每个消息。

然后可以使用广播消息（ Action Broadcaster ）来跟踪索引。

这是一些示例代码，用于给出总体思路：

MIDIThing::MIDIThing ()
{
    startTimer(1); //start a timer
}

void MIDIThing::start ()
{
    playstate = 1;
    startTime = Time::getCurrentTime().toMilliseconds();
}

void MIDIThing::timerCallback()
{
    if (playstate == 1) {
        Time::getMillisecondCounterHiRes();
        int64 target;
        if (Time::getCurrentTime().toMilliseconds() > target) {
            //fire off the message
        }

        //ended (possibly on a condition)
        ActionBroadcaster::sendActionMessage(FINISHED_PLAYBACK);
    }
}