Question

我正在使用Recorder.js录制音频，但如果我不使用耳机则会收到可怕的反馈。如果我使用我的苹果耳机，麦克风更接近耳机，甚至会有一些反馈。有没有办法降低麦克风/录音音量并阻止反馈？

Answer 1

如果您可以访问gain_node - 您可以控制输出扬声器音量

将此放入您的html（可选）

<p>Volume</p>
<input id="volume" type="range" min="0" max="1" step="0.1" value="0.5"/>

然后执行以下操作，其中U可以访问gain_node

  document.getElementById('volume').addEventListener('change', function() {

      var curr_volume = this.value;
      gain_node.gain.value = curr_volume;

      console.log("curr_volume ", curr_volume);
  });

下面我将上面的内容捆绑到一组对Web Audio API的调用中，我在其中有一个UI小部件，可以在收听麦克风时更改音量...在运行之前转动 DOWN 您的音量！

<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>capture microphone then show time & frequency domain output</title>

<script type="text/javascript">

var webaudio_tooling_obj = function () {

    var audioContext = new AudioContext();

    console.log("audio is starting up ...");

    var BUFF_SIZE_RENDERER = 16384;
    var SIZE_SHOW = 3; // number of array elements to show in console output

    var audioInput = null,
    microphone_stream = null,
    gain_node = null,
    script_processor_node = null,
    script_processor_analysis_node = null,
    analyser_node = null;

    if (!navigator.getUserMedia)
        navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia ||
    navigator.mozGetUserMedia || navigator.msGetUserMedia;

    if (navigator.getUserMedia){

        navigator.getUserMedia({audio:true}, 
            function(stream) {
                start_microphone(stream);
            },
            function(e) {
                alert('Error capturing audio.');
            }
            );

    } else { alert('getUserMedia not supported in this browser.'); }

    // ---

    function show_some_data(given_typed_array, num_row_to_display, label) {

        var size_buffer = given_typed_array.length;
        var index = 0;

        console.log("__________ " + label);

        if (label === "time") {

            for (; index < num_row_to_display && index < size_buffer; index += 1) {

                var curr_value_time = (given_typed_array[index] / 128) - 1.0;

                console.log(curr_value_time);
            }

        } else if (label === "frequency") {

            for (; index < num_row_to_display && index < size_buffer; index += 1) {

                console.log(given_typed_array[index]);
            }

        } else {

            throw new Error("ERROR - must pass time or frequency");
        }
    }

    function process_microphone_buffer(event) {

        var i, N, inp, microphone_output_buffer;

        // not needed for basic feature set
        // microphone_output_buffer = event.inputBuffer.getChannelData(0); // just mono - 1 channel for now
    }

    function start_microphone(stream){

        gain_node = audioContext.createGain();
        gain_node.connect( audioContext.destination );

        microphone_stream = audioContext.createMediaStreamSource(stream);
        microphone_stream.connect(gain_node); 

        script_processor_node = audioContext.createScriptProcessor(BUFF_SIZE_RENDERER, 1, 1);
        script_processor_node.onaudioprocess = process_microphone_buffer;

        microphone_stream.connect(script_processor_node);

        // --- enable volume control for output speakers

        document.getElementById('volume').addEventListener('change', function() {

            var curr_volume = this.value;
            gain_node.gain.value = curr_volume;

            console.log("curr_volume ", curr_volume);
        });

        // --- setup FFT

        script_processor_analysis_node = audioContext.createScriptProcessor(2048, 1, 1);
        script_processor_analysis_node.connect(gain_node);

        analyser_node = audioContext.createAnalyser();
        analyser_node.smoothingTimeConstant = 0;
        analyser_node.fftSize = 2048;

        microphone_stream.connect(analyser_node);

        analyser_node.connect(script_processor_analysis_node);

        var buffer_length = analyser_node.frequencyBinCount;

        var array_freq_domain = new Uint8Array(buffer_length);
        var array_time_domain = new Uint8Array(buffer_length);

        console.log("buffer_length " + buffer_length);

        script_processor_analysis_node.onaudioprocess = function() {

            // get the average for the first channel
            analyser_node.getByteFrequencyData(array_freq_domain);
            analyser_node.getByteTimeDomainData(array_time_domain);

            // draw the spectrogram
            if (microphone_stream.playbackState == microphone_stream.PLAYING_STATE) {

                show_some_data(array_freq_domain, SIZE_SHOW, "frequency");
                show_some_data(array_time_domain, SIZE_SHOW, "time"); // store this to record to aggregate buffer/file
            }
        };
    }

}(); //  webaudio_tooling_obj = function()

</script>

</head>
<body>

    <p>Volume</p>
    <input id="volume" type="range" min="0" max="1" step="0.1" value="0.0"/>

</body>
</html>

当然，由于您对输出音量进行了编程控制，因此无需UI小部件，因此要保持静音，您可以断开增益节点或将其设置为低

Answer 2

他们的example page (example_simple_exportwav.html)声明你应该戴耳机或调低音量。

在启用麦克风输入之前，请插入耳机或如果你想避免耳朵分裂反馈，请调低音量！

您可以在录制过程中静音或降低扬声器的音量：

我还测试了几个例子，从未体验过笔记本电脑扬声器的反馈。您可以发布您的代码，以便我们可以实时测试吗？

Record and Export Audio, Video files in browser using Web Audio API with Recorder.js - 底部的演示
http://webaudiodemos.appspot.com/AudioRecorder/index.html通过Web Audio Demos

有没有办法降低HTML5录音的录音音量以防止反馈？

2 个答案: