/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
var Guacamole = Guacamole || {};
/**
* Abstract audio player which accepts, queues and plays back arbitrary audio
* data. It is up to implementations of this class to provide some means of
* handling a provided Guacamole.InputStream. Data received along the provided
* stream is to be played back immediately.
*
* @constructor
*/
Guacamole.AudioPlayer = function AudioPlayer() {
/**
* Notifies this Guacamole.AudioPlayer that all audio up to the current
* point in time has been given via the underlying stream, and that any
* difference in time between queued audio data and the current time can be
* considered latency.
*/
this.sync = function sync() {
// Default implementation - do nothing
};
};
/**
* Determines whether the given mimetype is supported by any built-in
* implementation of Guacamole.AudioPlayer, and thus will be properly handled
* by Guacamole.AudioPlayer.getInstance().
*
* @param {!string} mimetype
* The mimetype to check.
*
* @returns {!boolean}
* true if the given mimetype is supported by any built-in
* Guacamole.AudioPlayer, false otherwise.
*/
Guacamole.AudioPlayer.isSupportedType = function isSupportedType(mimetype) {
return Guacamole.RawAudioPlayer.isSupportedType(mimetype);
};
/**
* Returns a list of all mimetypes supported by any built-in
* Guacamole.AudioPlayer, in rough order of priority. Beware that only the core
* mimetypes themselves will be listed. Any mimetype parameters, even required
* ones, will not be included in the list. For example, "audio/L8" is a
* supported raw audio mimetype that is supported, but it is invalid without
* additional parameters. Something like "audio/L8;rate=44100" would be valid,
* however (see https://tools.ietf.org/html/rfc4856).
*
* @returns {!string[]}
* A list of all mimetypes supported by any built-in Guacamole.AudioPlayer,
* excluding any parameters.
*/
Guacamole.AudioPlayer.getSupportedTypes = function getSupportedTypes() {
return Guacamole.RawAudioPlayer.getSupportedTypes();
};
/**
* Returns an instance of Guacamole.AudioPlayer providing support for the given
* audio format. If support for the given audio format is not available, null
* is returned.
*
* @param {!Guacamole.InputStream} stream
* The Guacamole.InputStream to read audio data from.
*
* @param {!string} mimetype
* The mimetype of the audio data in the provided stream.
*
* @return {Guacamole.AudioPlayer}
* A Guacamole.AudioPlayer instance supporting the given mimetype and
* reading from the given stream, or null if support for the given mimetype
* is absent.
*/
Guacamole.AudioPlayer.getInstance = function getInstance(stream, mimetype) {
// Use raw audio player if possible
if (Guacamole.RawAudioPlayer.isSupportedType(mimetype))
return new Guacamole.RawAudioPlayer(stream, mimetype);
// No support for given mimetype
return null;
};
/**
* Implementation of Guacamole.AudioPlayer providing support for raw PCM format
* audio. This player relies only on the Web Audio API and does not require any
* browser-level support for its audio formats.
*
* @constructor
* @augments Guacamole.AudioPlayer
* @param {!Guacamole.InputStream} stream
* The Guacamole.InputStream to read audio data from.
*
* @param {!string} mimetype
* The mimetype of the audio data in the provided stream, which must be a
* "audio/L8" or "audio/L16" mimetype with necessary parameters, such as:
* "audio/L16;rate=44100,channels=2".
*/
Guacamole.RawAudioPlayer = function RawAudioPlayer(stream, mimetype) {
/**
* The format of audio this player will decode.
*
* @private
* @type {Guacamole.RawAudioFormat}
*/
var format = Guacamole.RawAudioFormat.parse(mimetype);
/**
* An instance of a Web Audio API AudioContext object, or null if the
* Web Audio API is not supported.
*
* @private
* @type {AudioContext}
*/
var context = Guacamole.AudioContextFactory.getAudioContext();
/**
* The earliest possible time that the next packet could play without
* overlapping an already-playing packet, in seconds. Note that while this
* value is in seconds, it is not an integer value and has microsecond
* resolution.
*
* @private
* @type {!number}
*/
var nextPacketTime = context.currentTime;
/**
* Guacamole.ArrayBufferReader wrapped around the audio input stream
* provided with this Guacamole.RawAudioPlayer was created.
*
* @private
* @type {!Guacamole.ArrayBufferReader}
*/
var reader = new Guacamole.ArrayBufferReader(stream);
/**
* The minimum size of an audio packet split by splitAudioPacket(), in
* seconds. Audio packets smaller than this will not be split, nor will the
* split result of a larger packet ever be smaller in size than this
* minimum.
*
* @private
* @constant
* @type {!number}
*/
var MIN_SPLIT_SIZE = 0.02;
/**
* The maximum amount of latency to allow between the buffered data stream
* and the playback position, in seconds. Initially, this is set to
* roughly one third of a second.
*
* @private
* @type {!number}
*/
var maxLatency = 0.3;
/**
* The type of typed array that will be used to represent each audio packet
* internally. This will be either Int8Array or Int16Array, depending on
* whether the raw audio format is 8-bit or 16-bit.
*
* @private
* @constructor
*/
var SampleArray = (format.bytesPerSample === 1) ? window.Int8Array : window.Int16Array;
/**
* The maximum absolute value of any sample within a raw audio packet
* received by this audio player. This depends only on the size of each
* sample, and will be 128 for 8-bit audio and 32768 for 16-bit audio.
*
* @private
* @type {!number}
*/
var maxSampleValue = (format.bytesPerSample === 1) ? 128 : 32768;
/**
* The queue of all pending audio packets, as an array of sample arrays.
* Audio packets which are pending playback will be added to this queue for
* further manipulation prior to scheduling via the Web Audio API. Once an
* audio packet leaves this queue and is scheduled via the Web Audio API,
* no further modifications can be made to that packet.
*
* @private
* @type {!SampleArray[]}
*/
var packetQueue = [];
/**
* Given an array of audio packets, returns a single audio packet
* containing the concatenation of those packets.
*
* @private
* @param {!SampleArray[]} packets
* The array of audio packets to concatenate.
*
* @returns {SampleArray}
* A single audio packet containing the concatenation of all given
* audio packets. If no packets are provided, this will be undefined.
*/
var joinAudioPackets = function joinAudioPackets(packets) {
// Do not bother joining if one or fewer packets are in the queue
if (packets.length <= 1)
return packets[0];
// Determine total sample length of the entire queue
var totalLength = 0;
packets.forEach(function addPacketLengths(packet) {
totalLength += packet.length;
});
// Append each packet within queue
var offset = 0;
var joined = new SampleArray(totalLength);
packets.forEach(function appendPacket(packet) {
joined.set(packet, offset);
offset += packet.length;
});
return joined;
};
/**
* Given a single packet of audio data, splits off an arbitrary length of
* audio data from the beginning of that packet, returning the split result
* as an array of two packets. The split location is determined through an
* algorithm intended to minimize the liklihood of audible clicking between
* packets. If no such split location is possible, an array containing only
* the originally-provided audio packet is returned.
*
* @private
* @param {!SampleArray} data
* The audio packet to split.
*
* @returns {!SampleArray[]}
* An array of audio packets containing the result of splitting the
* provided audio packet. If splitting is possible, this array will
* contain two packets. If splitting is not possible, this array will
* contain only the originally-provided packet.
*/
var splitAudioPacket = function splitAudioPacket(data) {
var minValue = Number.MAX_VALUE;
var optimalSplitLength = data.length;
// Calculate number of whole samples in the provided audio packet AND
// in the minimum possible split packet
var samples = Math.floor(data.length / format.channels);
var minSplitSamples = Math.floor(format.rate * MIN_SPLIT_SIZE);
// Calculate the beginning of the "end" of the audio packet
var start = Math.max(
format.channels * minSplitSamples,
format.channels * (samples - minSplitSamples)
);
// For all samples at the end of the given packet, find a point where
// the perceptible volume across all channels is lowest (and thus is
// the optimal point to split)
for (var offset = start; offset < data.length; offset += format.channels) {
// Calculate the sum of all values across all channels (the result
// will be proportional to the average volume of a sample)
var totalValue = 0;
for (var channel = 0; channel < format.channels; channel++) {
totalValue += Math.abs(data[offset + channel]);
}
// If this is the smallest average value thus far, set the split
// length such that the first packet ends with the current sample
if (totalValue <= minValue) {
optimalSplitLength = offset + format.channels;
minValue = totalValue;
}
}
// If packet is not split, return the supplied packet untouched
if (optimalSplitLength === data.length)
return [data];
// Otherwise, split the packet into two new packets according to the
// calculated optimal split length
return [
new SampleArray(data.buffer.slice(0, optimalSplitLength * format.bytesPerSample)),
new SampleArray(data.buffer.slice(optimalSplitLength * format.bytesPerSample))
];
};
/**
* Pushes the given packet of audio data onto the playback queue. Unlike
* other private functions within Guacamole.RawAudioPlayer, the type of the
* ArrayBuffer packet of audio data here need not be specific to the type
* of audio (as with SampleArray). The ArrayBuffer type provided by a
* Guacamole.ArrayBufferReader, for example, is sufficient. Any necessary
* conversions will be performed automatically internally.
*
* @private
* @param {!ArrayBuffer} data
* A raw packet of audio data that should be pushed onto the audio
* playback queue.
*/
var pushAudioPacket = function pushAudioPacket(data) {
packetQueue.push(new SampleArray(data));
};
/**
* Shifts off and returns a packet of audio data from the beginning of the
* playback queue. The length of this audio packet is determined
* dynamically according to the click-reduction algorithm implemented by
* splitAudioPacket().
*
* @private
* @returns {SampleArray}
* A packet of audio data pulled from the beginning of the playback
* queue. If there is no audio currently in the playback queue, this
* will be null.
*/
var shiftAudioPacket = function shiftAudioPacket() {
// Flatten data in packet queue
var data = joinAudioPackets(packetQueue);
if (!data)
return null;
// Pull an appropriate amount of data from the front of the queue
packetQueue = splitAudioPacket(data);
data = packetQueue.shift();
return data;
};
/**
* Converts the given audio packet into an AudioBuffer, ready for playback
* by the Web Audio API. Unlike the raw audio packets received by this
* audio player, AudioBuffers require floating point samples and are split
* into isolated planes of channel-specific data.
*
* @private
* @param {!SampleArray} data
* The raw audio packet that should be converted into a Web Audio API
* AudioBuffer.
*
* @returns {!AudioBuffer}
* A new Web Audio API AudioBuffer containing the provided audio data,
* converted to the format used by the Web Audio API.
*/
var toAudioBuffer = function toAudioBuffer(data) {
// Calculate total number of samples
var samples = data.length / format.channels;
// Determine exactly when packet CAN play
var packetTime = context.currentTime;
if (nextPacketTime < packetTime)
nextPacketTime = packetTime;
// Get audio buffer for specified format
var audioBuffer = context.createBuffer(format.channels, samples, format.rate);
// Convert each channel
for (var channel = 0; channel < format.channels; channel++) {
var audioData = audioBuffer.getChannelData(channel);
// Fill audio buffer with data for channel
var offset = channel;
for (var i = 0; i < samples; i++) {
audioData[i] = data[offset] / maxSampleValue;
offset += format.channels;
}
}
return audioBuffer;
};
// Defer playback of received audio packets slightly
reader.ondata = function playReceivedAudio(data) {
// Push received samples onto queue
pushAudioPacket(new SampleArray(data));
// Shift off an arbitrary packet of audio data from the queue (this may
// be different in size from the packet just pushed)
var packet = shiftAudioPacket();
if (!packet)
return;
// Determine exactly when packet CAN play
var packetTime = context.currentTime;
if (nextPacketTime < packetTime)
nextPacketTime = packetTime;
// Set up buffer source
var source = context.createBufferSource();
source.connect(context.destination);
// Use noteOn() instead of start() if necessary
if (!source.start)
source.start = source.noteOn;
// Schedule packet
source.buffer = toAudioBuffer(packet);
source.start(nextPacketTime);
// Update timeline by duration of scheduled packet
nextPacketTime += packet.length / format.channels / format.rate;
};
/** @override */
this.sync = function sync() {
// Calculate elapsed time since last sync
var now = context.currentTime;
// Reschedule future playback time such that playback latency is
// bounded within a reasonable latency threshold
nextPacketTime = Math.min(nextPacketTime, now + maxLatency);
};
};
Guacamole.RawAudioPlayer.prototype = new Guacamole.AudioPlayer();
/**
* Determines whether the given mimetype is supported by
* Guacamole.RawAudioPlayer.
*
* @param {!string} mimetype
* The mimetype to check.
*
* @returns {!boolean}
* true if the given mimetype is supported by Guacamole.RawAudioPlayer,
* false otherwise.
*/
Guacamole.RawAudioPlayer.isSupportedType = function isSupportedType(mimetype) {
// No supported types if no Web Audio API
if (!Guacamole.AudioContextFactory.getAudioContext())
return false;
return Guacamole.RawAudioFormat.parse(mimetype) !== null;
};
/**
* Returns a list of all mimetypes supported by Guacamole.RawAudioPlayer. Only
* the core mimetypes themselves will be listed. Any mimetype parameters, even
* required ones, will not be included in the list. For example, "audio/L8" is
* a raw audio mimetype that may be supported, but it is invalid without
* additional parameters. Something like "audio/L8;rate=44100" would be valid,
* however (see https://tools.ietf.org/html/rfc4856).
*
* @returns {!string[]}
* A list of all mimetypes supported by Guacamole.RawAudioPlayer, excluding
* any parameters. If the necessary JavaScript APIs for playing raw audio
* are absent, this list will be empty.
*/
Guacamole.RawAudioPlayer.getSupportedTypes = function getSupportedTypes() {
// No supported types if no Web Audio API
if (!Guacamole.AudioContextFactory.getAudioContext())
return [];
// We support 8-bit and 16-bit raw PCM
return [
'audio/L8',
'audio/L16'
];
};