Question

我实现了一个简单的程序，它从Midi键盘输入，然后使用javax合成器接口输出相应的声音。这在我运行Windows的Pc上运行得非常好，但是，我想在运行Raspbian的Raspberry Pi上运行它。它实际上也可以工作，但是一旦我播放更多/更快的音符，声音开始抖动和噼啪声非常糟糕，我必须停止播放音符约2秒钟，以便抖动消失。我已经使用外部USB声音适配器，这实际上并没有多少帮助。这是处理midi输入的类：

public class MidiHandler {

    public MidiHandler() {
        MidiDevice device;
        MidiDevice.Info[] infos = MidiSystem.getMidiDeviceInfo();
        for (int i = 0; i < infos.length; i++) {
            try {
                device = MidiSystem.getMidiDevice(infos[i]);
                // does the device have any transmitters?
                // if it does, add it to the device list
                System.out.println(infos[i]);

                // get all transmitters
                List<Transmitter> transmitters = device.getTransmitters();
                // and for each transmitter

                for (int j = 0; j < transmitters.size(); j++) {
                    // create a new receiver
                    transmitters.get(j).setReceiver(
                    // using my own MidiInputReceiver
                            new MidiInputReceiver(device.getDeviceInfo()
                                    .toString()));
                }

                Transmitter trans = device.getTransmitter();
                trans.setReceiver(new MidiInputReceiver(device.getDeviceInfo()
                        .toString()));

                // open each device
                device.open();
                // if code gets this far without throwing an exception
                // print a success message
            } catch (MidiUnavailableException e) {
            }
        }

    }

    // tried to write my own class. I thought the send method handles an
    // MidiEvents sent to it
    public class MidiInputReceiver implements Receiver {
        Synthesizer synth;
        MidiChannel[] mc;
        Instrument[] instr;
        int instrument;
        int channel;



        public MidiInputReceiver(String name) {
            try
            {
                patcher p = new patcher();
                this.instrument = p.getInstrument();
                this.channel = p.getChannel();
                this.synth = MidiSystem.getSynthesizer();
                this.synth.open();
                this.mc = synth.getChannels();
                instr = synth.getDefaultSoundbank().getInstruments();
                this.synth.loadInstrument(instr[1]);
                mc[this.channel].programChange(0, this.instrument);
                System.out.println(this.channel + ", " + this.instrument);

            }
            catch (MidiUnavailableException e)
            {
                e.printStackTrace();
                System.exit(1);
            }
        }

        public void send(MidiMessage msg, long timeStamp) {
            /*
             * Use to display midi message
             * 
            for(int i = 0; i < msg.getMessage().length; i++) {
                System.out.print("[" + msg.getMessage()[i] + "] ");

            }
            System.out.println();
            */
            if (msg.getMessage()[0] == -112) {
                mc[this.channel].noteOn(msg.getMessage()[1], msg.getMessage()[2]+1000);
            }

            if (msg.getMessage()[0] == -128) {
                mc[this.channel].noteOff(msg.getMessage()[1], msg.getMessage()[2]+1000);
            }

        }

        public void close() {
        }
    }
}

这是由于Pi的硬件限制，还是我可以对此做些什么？

Answer 1

如果你有任何循环来更新midi检索/声音输出，可能会尝试在那里进行线程休眠以给操作系统时间做些什么？除此之外，不确定。由于某些原因，原始Raspberry Pi上的USB不是很好（很多错误，性能很慢 - 但这些确实在新的Linux /固件中有所修复）。您可能还需要修改采样率以匹配当前声音输出的理想设置（如果可以访问）（采样率不匹配意味着更多转换）。 Java可能会尝试使用理想作为默认值，但可能会被操作系统错误报告？

Midi输入树莓派

1 个答案: