var ids = [];

            var counter = 0;

​

            MediaStreamTrack.getSources( onStreamSources );

​

            function onStreamSources( sources ){

                var i = -1;

                var len = sources.length;

                var ids = [];

                while( ++i < len ){

                    if( sources[ i ].kind === "audio" ){

                        getAudioSource( sources[i].id );

                    } else {

                        getVideoSouce( sources[i].id );

                    }

                }

            }

​

            function getAudioSource( id ){

                counter++;

                navigator.webkitGetUserMedia({

                    "audio": {

                        "optional": [{

                            "sourceId": id

                        }]

                    },

                    "video": false

                }, onGetUserMedia("audio"), onGetUserMediaFail);

            }

​

            function getVideoSouce( id ){

                counter++;

                navigator.webkitGetUserMedia({

                    "video": {

                        "optional": [{

                            "sourceId": id

                        }]

                    },

                    "audio": false

                }, onGetUserMedia("video"), onGetUserMediaFail);

            }

​

            function onGetUserMedia( _type ){

                var type = _type === "audio" ? "getAudioTracks" : "getVideoTracks";

                return function( stream ){

                    var track = stream[type]()[0];

                    ids.push({

                        "label": track.label,

                        "sourceId": track.id

                    });

                    stream.stop();

                    counter--;

                    if( counter === 0 ){

                        console.log( ids );

                    }

                };

            }

​

            function onGetUserMediaFail(){

                console.log("error");

                counter--;

            }