将音频数据uri字符串转换为文件

Question

服务器将音频数据保存为base64数据字符串.移动Web客户端获取数据并播放音频.

但是在iOS和Android中的移动Chrome中发现了一个问题,即带有数据uri的音频无法播放(问题).

为了使它工作,我想知道在客户端是否有办法将数据字符串转换为音频文件(如.m4a)并将音频src链接到文件？

Answer 1

使用web audio api直接计算出来,在iOS和Android中的移动浏览器中具有最佳兼容性.

function base64ToArrayBuffer(base64) {
  var binaryString =  window.atob(base64);
  var len = binaryString.length;
  var bytes = new Uint8Array( len );
  for (var i = 0; i < len; i++)        {
    bytes[i] = binaryString.charCodeAt(i);
  }
  return bytes.buffer;
}

var base64 = '<data string retrieved from server>';
var audioContext = new (window.AudioContext || window.webkitAudioContext)();
var source = audioContext.createBufferSource();
audioContext.decodeAudioData(base64ToArrayBuffer(base64), function(buffer) {
   source.buffer = buffer;
   source.connect(audioContext.destination);
   source.start(0);
});

它适用于iOS Safari,Chrome和Android默认浏览器以及Chrome.

Answer 2

有一种方法可以做你想要的东西,它适用于桌面,但我不能保证它适用于移动设备.我们的想法是将dataURI转换为ArrayBuffer,从中构造一个Blob,然后用它创建一个ObjectURL,传递给audio元素.这是代码(我在Linux下的Chrome/Firefox中进行了测试,它的工作原理):

<script>
    var base64audio = "data:audio/ogg;base64,gibberish";

    function dataURItoBlob(dataURI)
    {
        // Split the input to get the mime-type and the data itself
        dataURI = dataURI.split( ',' );

        // First part contains data:audio/ogg;base64 from which we only need audio/ogg
        var type = dataURI[ 0 ].split( ':' )[ 1 ].split( ';' )[ 0 ];

        // Second part is the data itself and we decode it
        var byteString = atob( dataURI[ 1 ] );
        var byteStringLen = byteString.length;

        // Create ArrayBuffer with the byte string and set the length to it
        var ab = new ArrayBuffer( byteStringLen );

        // Create a typed array out of the array buffer representing each character from as a 8-bit unsigned integer
        var intArray = new Uint8Array( ab );
        for ( var i = 0; i < byteStringLen; i++ ) 
        {
            intArray[ i ] = byteString.charCodeAt( i );
        }

        return new Blob( [ intArray ], {type: type} );
    }
    document.addEventListener( 'DOMContentLoaded', function()
    {
        // Construct an URL from the Blob. This URL will remain valid until user closes the tab or you revoke it
        // Make sure at some point (when you don't need the audio anymore) to do URL.revokeObjectURL() with the constructed URL
        var objectURL = URL.createObjectURL(dataURItoBlob(base64audio));

        // Pass the URL to the audio element and load it
        var audio = document.getElementById( 'test' );
        audio.src = objectURL;
        audio.load();
    } );
</script>
...
<audio id="test" controls />

我希望有所帮助;)