@sqhead/mux.js
Version:
A collection of lightweight utilities for inspecting and manipulating video container formats.
1,600 lines (1,404 loc) • 161 kB
JavaScript
/**
* Copyright 2015 Brightcove
*
* Licensed 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.
*/
(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.muxjs = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
/**
* mux.js
*
* Copyright (c) 2016 Brightcove
* All rights reserved.
*
* A stream-based aac to mp4 converter. This utility can be used to
* deliver mp4s to a SourceBuffer on platforms that support native
* Media Source Extensions.
*/
'use strict';
var Stream = require('../utils/stream.js');
// Constants
var AacStream;
/**
* Splits an incoming stream of binary data into ADTS and ID3 Frames.
*/
AacStream = function() {
var
everything = new Uint8Array(),
timeStamp = 0;
AacStream.prototype.init.call(this);
this.setTimestamp = function(timestamp) {
timeStamp = timestamp;
};
this.parseId3TagSize = function(header, byteIndex) {
var
returnSize = (header[byteIndex + 6] << 21) |
(header[byteIndex + 7] << 14) |
(header[byteIndex + 8] << 7) |
(header[byteIndex + 9]),
flags = header[byteIndex + 5],
footerPresent = (flags & 16) >> 4;
if (footerPresent) {
return returnSize + 20;
}
return returnSize + 10;
};
this.parseAdtsSize = function(header, byteIndex) {
var
lowThree = (header[byteIndex + 5] & 0xE0) >> 5,
middle = header[byteIndex + 4] << 3,
highTwo = header[byteIndex + 3] & 0x3 << 11;
return (highTwo | middle) | lowThree;
};
this.push = function(bytes) {
var
frameSize = 0,
byteIndex = 0,
bytesLeft,
chunk,
packet,
tempLength;
// If there are bytes remaining from the last segment, prepend them to the
// bytes that were pushed in
if (everything.length) {
tempLength = everything.length;
everything = new Uint8Array(bytes.byteLength + tempLength);
everything.set(everything.subarray(0, tempLength));
everything.set(bytes, tempLength);
} else {
everything = bytes;
}
while (everything.length - byteIndex >= 3) {
if ((everything[byteIndex] === 'I'.charCodeAt(0)) &&
(everything[byteIndex + 1] === 'D'.charCodeAt(0)) &&
(everything[byteIndex + 2] === '3'.charCodeAt(0))) {
// Exit early because we don't have enough to parse
// the ID3 tag header
if (everything.length - byteIndex < 10) {
break;
}
// check framesize
frameSize = this.parseId3TagSize(everything, byteIndex);
// Exit early if we don't have enough in the buffer
// to emit a full packet
if (frameSize > everything.length) {
break;
}
chunk = {
type: 'timed-metadata',
data: everything.subarray(byteIndex, byteIndex + frameSize)
};
this.trigger('data', chunk);
byteIndex += frameSize;
continue;
} else if ((everything[byteIndex] & 0xff === 0xff) &&
((everything[byteIndex + 1] & 0xf0) === 0xf0)) {
// Exit early because we don't have enough to parse
// the ADTS frame header
if (everything.length - byteIndex < 7) {
break;
}
frameSize = this.parseAdtsSize(everything, byteIndex);
// Exit early if we don't have enough in the buffer
// to emit a full packet
if (frameSize > everything.length) {
break;
}
packet = {
type: 'audio',
data: everything.subarray(byteIndex, byteIndex + frameSize),
pts: timeStamp,
dts: timeStamp
};
this.trigger('data', packet);
byteIndex += frameSize;
continue;
}
byteIndex++;
}
bytesLeft = everything.length - byteIndex;
if (bytesLeft > 0) {
everything = everything.subarray(byteIndex);
} else {
everything = new Uint8Array();
}
};
};
AacStream.prototype = new Stream();
module.exports = AacStream;
},{"../utils/stream.js":17}],2:[function(require,module,exports){
'use strict';
var Stream = require('../utils/stream.js');
var AdtsStream;
var
ADTS_SAMPLING_FREQUENCIES = [
96000,
88200,
64000,
48000,
44100,
32000,
24000,
22050,
16000,
12000,
11025,
8000,
7350
];
/*
* Accepts a ElementaryStream and emits data events with parsed
* AAC Audio Frames of the individual packets. Input audio in ADTS
* format is unpacked and re-emitted as AAC frames.
*
* @see http://wiki.multimedia.cx/index.php?title=ADTS
* @see http://wiki.multimedia.cx/?title=Understanding_AAC
*/
AdtsStream = function() {
var buffer;
AdtsStream.prototype.init.call(this);
this.push = function(packet) {
var
i = 0,
frameNum = 0,
frameLength,
protectionSkipBytes,
frameEnd,
oldBuffer,
sampleCount,
adtsFrameDuration;
if (packet.type !== 'audio') {
// ignore non-audio data
return;
}
// Prepend any data in the buffer to the input data so that we can parse
// aac frames the cross a PES packet boundary
if (buffer) {
oldBuffer = buffer;
buffer = new Uint8Array(oldBuffer.byteLength + packet.data.byteLength);
buffer.set(oldBuffer);
buffer.set(packet.data, oldBuffer.byteLength);
} else {
buffer = packet.data;
}
// unpack any ADTS frames which have been fully received
// for details on the ADTS header, see http://wiki.multimedia.cx/index.php?title=ADTS
while (i + 5 < buffer.length) {
// Loook for the start of an ADTS header..
if (buffer[i] !== 0xFF || (buffer[i + 1] & 0xF6) !== 0xF0) {
// If a valid header was not found, jump one forward and attempt to
// find a valid ADTS header starting at the next byte
i++;
continue;
}
// The protection skip bit tells us if we have 2 bytes of CRC data at the
// end of the ADTS header
protectionSkipBytes = (~buffer[i + 1] & 0x01) * 2;
// Frame length is a 13 bit integer starting 16 bits from the
// end of the sync sequence
frameLength = ((buffer[i + 3] & 0x03) << 11) |
(buffer[i + 4] << 3) |
((buffer[i + 5] & 0xe0) >> 5);
sampleCount = ((buffer[i + 6] & 0x03) + 1) * 1024;
adtsFrameDuration = (sampleCount * 90000) /
ADTS_SAMPLING_FREQUENCIES[(buffer[i + 2] & 0x3c) >>> 2];
frameEnd = i + frameLength;
// If we don't have enough data to actually finish this ADTS frame, return
// and wait for more data
if (buffer.byteLength < frameEnd) {
return;
}
// Otherwise, deliver the complete AAC frame
this.trigger('data', {
pts: packet.pts + (frameNum * adtsFrameDuration),
dts: packet.dts + (frameNum * adtsFrameDuration),
sampleCount: sampleCount,
audioobjecttype: ((buffer[i + 2] >>> 6) & 0x03) + 1,
channelcount: ((buffer[i + 2] & 1) << 2) |
((buffer[i + 3] & 0xc0) >>> 6),
samplerate: ADTS_SAMPLING_FREQUENCIES[(buffer[i + 2] & 0x3c) >>> 2],
samplingfrequencyindex: (buffer[i + 2] & 0x3c) >>> 2,
// assume ISO/IEC 14496-12 AudioSampleEntry default of 16
samplesize: 16,
data: buffer.subarray(i + 7 + protectionSkipBytes, frameEnd)
});
// If the buffer is empty, clear it and return
if (buffer.byteLength === frameEnd) {
buffer = undefined;
return;
}
frameNum++;
// Remove the finished frame from the buffer and start the process again
buffer = buffer.subarray(frameEnd);
}
};
this.flush = function() {
this.trigger('done');
};
};
AdtsStream.prototype = new Stream();
module.exports = AdtsStream;
},{"../utils/stream.js":17}],3:[function(require,module,exports){
'use strict';
var Stream = require('../utils/stream.js');
var ExpGolomb = require('../utils/exp-golomb.js');
var H264Stream, NalByteStream;
var PROFILES_WITH_OPTIONAL_SPS_DATA;
/**
* Accepts a NAL unit byte stream and unpacks the embedded NAL units.
*/
NalByteStream = function() {
var
syncPoint = 0,
i,
buffer;
NalByteStream.prototype.init.call(this);
this.push = function(data) {
var swapBuffer;
if (!buffer) {
buffer = data.data;
} else {
swapBuffer = new Uint8Array(buffer.byteLength + data.data.byteLength);
swapBuffer.set(buffer);
swapBuffer.set(data.data, buffer.byteLength);
buffer = swapBuffer;
}
// Rec. ITU-T H.264, Annex B
// scan for NAL unit boundaries
// a match looks like this:
// 0 0 1 .. NAL .. 0 0 1
// ^ sync point ^ i
// or this:
// 0 0 1 .. NAL .. 0 0 0
// ^ sync point ^ i
// advance the sync point to a NAL start, if necessary
for (; syncPoint < buffer.byteLength - 3; syncPoint++) {
if (buffer[syncPoint + 2] === 1) {
// the sync point is properly aligned
i = syncPoint + 5;
break;
}
}
while (i < buffer.byteLength) {
// look at the current byte to determine if we've hit the end of
// a NAL unit boundary
switch (buffer[i]) {
case 0:
// skip past non-sync sequences
if (buffer[i - 1] !== 0) {
i += 2;
break;
} else if (buffer[i - 2] !== 0) {
i++;
break;
}
// deliver the NAL unit if it isn't empty
if (syncPoint + 3 !== i - 2) {
this.trigger('data', buffer.subarray(syncPoint + 3, i - 2));
}
// drop trailing zeroes
do {
i++;
} while (buffer[i] !== 1 && i < buffer.length);
syncPoint = i - 2;
i += 3;
break;
case 1:
// skip past non-sync sequences
if (buffer[i - 1] !== 0 ||
buffer[i - 2] !== 0) {
i += 3;
break;
}
// deliver the NAL unit
this.trigger('data', buffer.subarray(syncPoint + 3, i - 2));
syncPoint = i - 2;
i += 3;
break;
default:
// the current byte isn't a one or zero, so it cannot be part
// of a sync sequence
i += 3;
break;
}
}
// filter out the NAL units that were delivered
buffer = buffer.subarray(syncPoint);
i -= syncPoint;
syncPoint = 0;
};
this.flush = function() {
// deliver the last buffered NAL unit
if (buffer && buffer.byteLength > 3) {
this.trigger('data', buffer.subarray(syncPoint + 3));
}
// reset the stream state
buffer = null;
syncPoint = 0;
this.trigger('done');
};
};
NalByteStream.prototype = new Stream();
// values of profile_idc that indicate additional fields are included in the SPS
// see Recommendation ITU-T H.264 (4/2013),
// 7.3.2.1.1 Sequence parameter set data syntax
PROFILES_WITH_OPTIONAL_SPS_DATA = {
100: true,
110: true,
122: true,
244: true,
44: true,
83: true,
86: true,
118: true,
128: true,
138: true,
139: true,
134: true
};
/**
* Accepts input from a ElementaryStream and produces H.264 NAL unit data
* events.
*/
H264Stream = function() {
var
nalByteStream = new NalByteStream(),
self,
trackId,
currentPts,
currentDts,
discardEmulationPreventionBytes,
readSequenceParameterSet,
skipScalingList;
H264Stream.prototype.init.call(this);
self = this;
this.push = function(packet) {
if (packet.type !== 'video') {
return;
}
trackId = packet.trackId;
currentPts = packet.pts;
currentDts = packet.dts;
nalByteStream.push(packet);
};
nalByteStream.on('data', function(data) {
var
event = {
trackId: trackId,
pts: currentPts,
dts: currentDts,
data: data
};
switch (data[0] & 0x1f) {
case 0x05:
event.nalUnitType = 'slice_layer_without_partitioning_rbsp_idr';
break;
case 0x06:
event.nalUnitType = 'sei_rbsp';
event.escapedRBSP = discardEmulationPreventionBytes(data.subarray(1));
break;
case 0x07:
event.nalUnitType = 'seq_parameter_set_rbsp';
event.escapedRBSP = discardEmulationPreventionBytes(data.subarray(1));
event.config = readSequenceParameterSet(event.escapedRBSP);
break;
case 0x08:
event.nalUnitType = 'pic_parameter_set_rbsp';
break;
case 0x09:
event.nalUnitType = 'access_unit_delimiter_rbsp';
break;
default:
break;
}
self.trigger('data', event);
});
nalByteStream.on('done', function() {
self.trigger('done');
});
this.flush = function() {
nalByteStream.flush();
};
/**
* Advance the ExpGolomb decoder past a scaling list. The scaling
* list is optionally transmitted as part of a sequence parameter
* set and is not relevant to transmuxing.
* @param count {number} the number of entries in this scaling list
* @param expGolombDecoder {object} an ExpGolomb pointed to the
* start of a scaling list
* @see Recommendation ITU-T H.264, Section 7.3.2.1.1.1
*/
skipScalingList = function(count, expGolombDecoder) {
var
lastScale = 8,
nextScale = 8,
j,
deltaScale;
for (j = 0; j < count; j++) {
if (nextScale !== 0) {
deltaScale = expGolombDecoder.readExpGolomb();
nextScale = (lastScale + deltaScale + 256) % 256;
}
lastScale = (nextScale === 0) ? lastScale : nextScale;
}
};
/**
* Expunge any "Emulation Prevention" bytes from a "Raw Byte
* Sequence Payload"
* @param data {Uint8Array} the bytes of a RBSP from a NAL
* unit
* @return {Uint8Array} the RBSP without any Emulation
* Prevention Bytes
*/
discardEmulationPreventionBytes = function(data) {
var
length = data.byteLength,
emulationPreventionBytesPositions = [],
i = 1,
newLength, newData;
// Find all `Emulation Prevention Bytes`
while (i < length - 2) {
if (data[i] === 0 && data[i + 1] === 0 && data[i + 2] === 0x03) {
emulationPreventionBytesPositions.push(i + 2);
i += 2;
} else {
i++;
}
}
// If no Emulation Prevention Bytes were found just return the original
// array
if (emulationPreventionBytesPositions.length === 0) {
return data;
}
// Create a new array to hold the NAL unit data
newLength = length - emulationPreventionBytesPositions.length;
newData = new Uint8Array(newLength);
var sourceIndex = 0;
for (i = 0; i < newLength; sourceIndex++, i++) {
if (sourceIndex === emulationPreventionBytesPositions[0]) {
// Skip this byte
sourceIndex++;
// Remove this position index
emulationPreventionBytesPositions.shift();
}
newData[i] = data[sourceIndex];
}
return newData;
};
/**
* Read a sequence parameter set and return some interesting video
* properties. A sequence parameter set is the H264 metadata that
* describes the properties of upcoming video frames.
* @param data {Uint8Array} the bytes of a sequence parameter set
* @return {object} an object with configuration parsed from the
* sequence parameter set, including the dimensions of the
* associated video frames.
*/
readSequenceParameterSet = function(data) {
var
frameCropLeftOffset = 0,
frameCropRightOffset = 0,
frameCropTopOffset = 0,
frameCropBottomOffset = 0,
sarScale = 1,
expGolombDecoder, profileIdc, levelIdc, profileCompatibility,
chromaFormatIdc, picOrderCntType,
numRefFramesInPicOrderCntCycle, picWidthInMbsMinus1,
picHeightInMapUnitsMinus1,
frameMbsOnlyFlag,
scalingListCount,
sarRatio,
aspectRatioIdc,
i;
expGolombDecoder = new ExpGolomb(data);
profileIdc = expGolombDecoder.readUnsignedByte(); // profile_idc
profileCompatibility = expGolombDecoder.readUnsignedByte(); // constraint_set[0-5]_flag
levelIdc = expGolombDecoder.readUnsignedByte(); // level_idc u(8)
expGolombDecoder.skipUnsignedExpGolomb(); // seq_parameter_set_id
// some profiles have more optional data we don't need
if (PROFILES_WITH_OPTIONAL_SPS_DATA[profileIdc]) {
chromaFormatIdc = expGolombDecoder.readUnsignedExpGolomb();
if (chromaFormatIdc === 3) {
expGolombDecoder.skipBits(1); // separate_colour_plane_flag
}
expGolombDecoder.skipUnsignedExpGolomb(); // bit_depth_luma_minus8
expGolombDecoder.skipUnsignedExpGolomb(); // bit_depth_chroma_minus8
expGolombDecoder.skipBits(1); // qpprime_y_zero_transform_bypass_flag
if (expGolombDecoder.readBoolean()) { // seq_scaling_matrix_present_flag
scalingListCount = (chromaFormatIdc !== 3) ? 8 : 12;
for (i = 0; i < scalingListCount; i++) {
if (expGolombDecoder.readBoolean()) { // seq_scaling_list_present_flag[ i ]
if (i < 6) {
skipScalingList(16, expGolombDecoder);
} else {
skipScalingList(64, expGolombDecoder);
}
}
}
}
}
expGolombDecoder.skipUnsignedExpGolomb(); // log2_max_frame_num_minus4
picOrderCntType = expGolombDecoder.readUnsignedExpGolomb();
if (picOrderCntType === 0) {
expGolombDecoder.readUnsignedExpGolomb(); // log2_max_pic_order_cnt_lsb_minus4
} else if (picOrderCntType === 1) {
expGolombDecoder.skipBits(1); // delta_pic_order_always_zero_flag
expGolombDecoder.skipExpGolomb(); // offset_for_non_ref_pic
expGolombDecoder.skipExpGolomb(); // offset_for_top_to_bottom_field
numRefFramesInPicOrderCntCycle = expGolombDecoder.readUnsignedExpGolomb();
for (i = 0; i < numRefFramesInPicOrderCntCycle; i++) {
expGolombDecoder.skipExpGolomb(); // offset_for_ref_frame[ i ]
}
}
expGolombDecoder.skipUnsignedExpGolomb(); // max_num_ref_frames
expGolombDecoder.skipBits(1); // gaps_in_frame_num_value_allowed_flag
picWidthInMbsMinus1 = expGolombDecoder.readUnsignedExpGolomb();
picHeightInMapUnitsMinus1 = expGolombDecoder.readUnsignedExpGolomb();
frameMbsOnlyFlag = expGolombDecoder.readBits(1);
if (frameMbsOnlyFlag === 0) {
expGolombDecoder.skipBits(1); // mb_adaptive_frame_field_flag
}
expGolombDecoder.skipBits(1); // direct_8x8_inference_flag
if (expGolombDecoder.readBoolean()) { // frame_cropping_flag
frameCropLeftOffset = expGolombDecoder.readUnsignedExpGolomb();
frameCropRightOffset = expGolombDecoder.readUnsignedExpGolomb();
frameCropTopOffset = expGolombDecoder.readUnsignedExpGolomb();
frameCropBottomOffset = expGolombDecoder.readUnsignedExpGolomb();
}
if (expGolombDecoder.readBoolean()) {
// vui_parameters_present_flag
if (expGolombDecoder.readBoolean()) {
// aspect_ratio_info_present_flag
aspectRatioIdc = expGolombDecoder.readUnsignedByte();
switch (aspectRatioIdc) {
case 1: sarRatio = [1, 1]; break;
case 2: sarRatio = [12, 11]; break;
case 3: sarRatio = [10, 11]; break;
case 4: sarRatio = [16, 11]; break;
case 5: sarRatio = [40, 33]; break;
case 6: sarRatio = [24, 11]; break;
case 7: sarRatio = [20, 11]; break;
case 8: sarRatio = [32, 11]; break;
case 9: sarRatio = [80, 33]; break;
case 10: sarRatio = [18, 11]; break;
case 11: sarRatio = [15, 11]; break;
case 12: sarRatio = [64, 33]; break;
case 13: sarRatio = [160, 99]; break;
case 14: sarRatio = [4, 3]; break;
case 15: sarRatio = [3, 2]; break;
case 16: sarRatio = [2, 1]; break;
case 255: {
sarRatio = [expGolombDecoder.readUnsignedByte() << 8 |
expGolombDecoder.readUnsignedByte(),
expGolombDecoder.readUnsignedByte() << 8 |
expGolombDecoder.readUnsignedByte() ];
break;
}
}
if (sarRatio) {
sarScale = sarRatio[0] / sarRatio[1];
}
}
}
return {
profileIdc: profileIdc,
levelIdc: levelIdc,
profileCompatibility: profileCompatibility,
width: Math.ceil((((picWidthInMbsMinus1 + 1) * 16) - frameCropLeftOffset * 2 - frameCropRightOffset * 2) * sarScale),
height: ((2 - frameMbsOnlyFlag) * (picHeightInMapUnitsMinus1 + 1) * 16) - (frameCropTopOffset * 2) - (frameCropBottomOffset * 2)
};
};
};
H264Stream.prototype = new Stream();
module.exports = {
H264Stream: H264Stream,
NalByteStream: NalByteStream
};
},{"../utils/exp-golomb.js":16,"../utils/stream.js":17}],4:[function(require,module,exports){
var highPrefix = [33, 16, 5, 32, 164, 27];
var lowPrefix = [33, 65, 108, 84, 1, 2, 4, 8, 168, 2, 4, 8, 17, 191, 252];
var zeroFill = function(count) {
var a = [];
while (count--) {
a.push(0);
}
return a;
};
var makeTable = function(metaTable) {
return Object.keys(metaTable).reduce(function(obj, key) {
obj[key] = new Uint8Array(metaTable[key].reduce(function(arr, part) {
return arr.concat(part);
}, []));
return obj;
}, {});
};
// Frames-of-silence to use for filling in missing AAC frames
var coneOfSilence = {
96000: [highPrefix, [227, 64], zeroFill(154), [56]],
88200: [highPrefix, [231], zeroFill(170), [56]],
64000: [highPrefix, [248, 192], zeroFill(240), [56]],
48000: [highPrefix, [255, 192], zeroFill(268), [55, 148, 128], zeroFill(54), [112]],
44100: [highPrefix, [255, 192], zeroFill(268), [55, 163, 128], zeroFill(84), [112]],
32000: [highPrefix, [255, 192], zeroFill(268), [55, 234], zeroFill(226), [112]],
24000: [highPrefix, [255, 192], zeroFill(268), [55, 255, 128], zeroFill(268), [111, 112], zeroFill(126), [224]],
16000: [highPrefix, [255, 192], zeroFill(268), [55, 255, 128], zeroFill(268), [111, 255], zeroFill(269), [223, 108], zeroFill(195), [1, 192]],
12000: [lowPrefix, zeroFill(268), [3, 127, 248], zeroFill(268), [6, 255, 240], zeroFill(268), [13, 255, 224], zeroFill(268), [27, 253, 128], zeroFill(259), [56]],
11025: [lowPrefix, zeroFill(268), [3, 127, 248], zeroFill(268), [6, 255, 240], zeroFill(268), [13, 255, 224], zeroFill(268), [27, 255, 192], zeroFill(268), [55, 175, 128], zeroFill(108), [112]],
8000: [lowPrefix, zeroFill(268), [3, 121, 16], zeroFill(47), [7]]
};
module.exports = makeTable(coneOfSilence);
},{}],5:[function(require,module,exports){
/**
* mux.js
*
* Copyright (c) 2015 Brightcove
* All rights reserved.
*
* Reads in-band caption information from a video elementary
* stream. Captions must follow the CEA-708 standard for injection
* into an MPEG-2 transport streams.
* @see https://en.wikipedia.org/wiki/CEA-708
* @see https://www.gpo.gov/fdsys/pkg/CFR-2007-title47-vol1/pdf/CFR-2007-title47-vol1-sec15-119.pdf
*/
'use strict';
// -----------------
// Link To Transport
// -----------------
// Supplemental enhancement information (SEI) NAL units have a
// payload type field to indicate how they are to be
// interpreted. CEAS-708 caption content is always transmitted with
// payload type 0x04.
var USER_DATA_REGISTERED_ITU_T_T35 = 4,
RBSP_TRAILING_BITS = 128,
Stream = require('../utils/stream');
/**
* Parse a supplemental enhancement information (SEI) NAL unit.
* Stops parsing once a message of type ITU T T35 has been found.
*
* @param bytes {Uint8Array} the bytes of a SEI NAL unit
* @return {object} the parsed SEI payload
* @see Rec. ITU-T H.264, 7.3.2.3.1
*/
var parseSei = function(bytes) {
var
i = 0,
result = {
payloadType: -1,
payloadSize: 0
},
payloadType = 0,
payloadSize = 0;
// go through the sei_rbsp parsing each each individual sei_message
while (i < bytes.byteLength) {
// stop once we have hit the end of the sei_rbsp
if (bytes[i] === RBSP_TRAILING_BITS) {
break;
}
// Parse payload type
while (bytes[i] === 0xFF) {
payloadType += 255;
i++;
}
payloadType += bytes[i++];
// Parse payload size
while (bytes[i] === 0xFF) {
payloadSize += 255;
i++;
}
payloadSize += bytes[i++];
// this sei_message is a 608/708 caption so save it and break
// there can only ever be one caption message in a frame's sei
if (!result.payload && payloadType === USER_DATA_REGISTERED_ITU_T_T35) {
result.payloadType = payloadType;
result.payloadSize = payloadSize;
result.payload = bytes.subarray(i, i + payloadSize);
break;
}
// skip the payload and parse the next message
i += payloadSize;
payloadType = 0;
payloadSize = 0;
}
return result;
};
// see ANSI/SCTE 128-1 (2013), section 8.1
var parseUserData = function(sei) {
// itu_t_t35_contry_code must be 181 (United States) for
// captions
if (sei.payload[0] !== 181) {
return null;
}
// itu_t_t35_provider_code should be 49 (ATSC) for captions
if (((sei.payload[1] << 8) | sei.payload[2]) !== 49) {
return null;
}
// the user_identifier should be "GA94" to indicate ATSC1 data
if (String.fromCharCode(sei.payload[3],
sei.payload[4],
sei.payload[5],
sei.payload[6]) !== 'GA94') {
return null;
}
// finally, user_data_type_code should be 0x03 for caption data
if (sei.payload[7] !== 0x03) {
return null;
}
// return the user_data_type_structure and strip the trailing
// marker bits
return sei.payload.subarray(8, sei.payload.length - 1);
};
// see CEA-708-D, section 4.4
var parseCaptionPackets = function(pts, userData) {
var results = [], i, count, offset, data;
// if this is just filler, return immediately
if (!(userData[0] & 0x40)) {
return results;
}
// parse out the cc_data_1 and cc_data_2 fields
count = userData[0] & 0x1f;
for (i = 0; i < count; i++) {
offset = i * 3;
data = {
type: userData[offset + 2] & 0x03,
pts: pts
};
// capture cc data when cc_valid is 1
if (userData[offset + 2] & 0x04) {
data.ccData = (userData[offset + 3] << 8) | userData[offset + 4];
results.push(data);
}
}
return results;
};
var CaptionStream = function() {
CaptionStream.prototype.init.call(this);
this.captionPackets_ = [];
this.ccStreams_ = [
new Cea608Stream(0, 0), // eslint-disable-line no-use-before-define
new Cea608Stream(0, 1), // eslint-disable-line no-use-before-define
new Cea608Stream(1, 0), // eslint-disable-line no-use-before-define
new Cea608Stream(1, 1) // eslint-disable-line no-use-before-define
];
this.reset();
// forward data and done events from CCs to this CaptionStream
this.ccStreams_.forEach(function(cc) {
cc.on('data', this.trigger.bind(this, 'data'));
cc.on('done', this.trigger.bind(this, 'done'));
}, this);
};
CaptionStream.prototype = new Stream();
CaptionStream.prototype.push = function(event) {
var sei, userData;
// only examine SEI NALs
if (event.nalUnitType !== 'sei_rbsp') {
return;
}
// parse the sei
sei = parseSei(event.escapedRBSP);
// ignore everything but user_data_registered_itu_t_t35
if (sei.payloadType !== USER_DATA_REGISTERED_ITU_T_T35) {
return;
}
// parse out the user data payload
userData = parseUserData(sei);
// ignore unrecognized userData
if (!userData) {
return;
}
// Sometimes, the same segment # will be downloaded twice. To stop the
// caption data from being processed twice, we track the latest dts we've
// received and ignore everything with a dts before that. However, since
// data for a specific dts can be split across packets on either side of
// a segment boundary, we need to make sure we *don't* ignore the packets
// from the *next* segment that have dts === this.latestDts_. By constantly
// tracking the number of packets received with dts === this.latestDts_, we
// know how many should be ignored once we start receiving duplicates.
if (event.dts < this.latestDts_) {
// We've started getting older data, so set the flag.
this.ignoreNextEqualDts_ = true;
return;
} else if ((event.dts === this.latestDts_) && (this.ignoreNextEqualDts_)) {
this.numSameDts_--;
if (!this.numSameDts_) {
// We've received the last duplicate packet, time to start processing again
this.ignoreNextEqualDts_ = false;
}
return;
}
// parse out CC data packets and save them for later
this.captionPackets_ = this.captionPackets_.concat(parseCaptionPackets(event.pts, userData));
if (this.latestDts_ !== event.dts) {
this.numSameDts_ = 0;
}
this.numSameDts_++;
this.latestDts_ = event.dts;
};
CaptionStream.prototype.flush = function() {
// make sure we actually parsed captions before proceeding
if (!this.captionPackets_.length) {
this.ccStreams_.forEach(function(cc) {
cc.flush();
}, this);
return;
}
// In Chrome, the Array#sort function is not stable so add a
// presortIndex that we can use to ensure we get a stable-sort
this.captionPackets_.forEach(function(elem, idx) {
elem.presortIndex = idx;
});
// sort caption byte-pairs based on their PTS values
this.captionPackets_.sort(function(a, b) {
if (a.pts === b.pts) {
return a.presortIndex - b.presortIndex;
}
return a.pts - b.pts;
});
this.captionPackets_.forEach(function(packet) {
if (packet.type < 2) {
// Dispatch packet to the right Cea608Stream
this.dispatchCea608Packet(packet);
}
// this is where an 'else' would go for a dispatching packets
// to a theoretical Cea708Stream that handles SERVICEn data
}, this);
this.captionPackets_.length = 0;
this.ccStreams_.forEach(function(cc) {
cc.flush();
}, this);
return;
};
CaptionStream.prototype.reset = function() {
this.latestDts_ = null;
this.ignoreNextEqualDts_ = false;
this.numSameDts_ = 0;
this.activeCea608Channel_ = [null, null];
this.ccStreams_.forEach(function(ccStream) {
ccStream.reset();
});
};
CaptionStream.prototype.dispatchCea608Packet = function(packet) {
// NOTE: packet.type is the CEA608 field
if (this.setsChannel1Active(packet)) {
this.activeCea608Channel_[packet.type] = 0;
} else if (this.setsChannel2Active(packet)) {
this.activeCea608Channel_[packet.type] = 1;
}
if (this.activeCea608Channel_[packet.type] === null) {
// If we haven't received anything to set the active channel, discard the
// data; we don't want jumbled captions
return;
}
this.ccStreams_[(packet.type << 1) + this.activeCea608Channel_[packet.type]].push(packet);
};
CaptionStream.prototype.setsChannel1Active = function(packet) {
return ((packet.ccData & 0x7800) === 0x1000);
};
CaptionStream.prototype.setsChannel2Active = function(packet) {
return ((packet.ccData & 0x7800) === 0x1800);
};
// ----------------------
// Session to Application
// ----------------------
var CHARACTER_TRANSLATION = {
0x2a: 0xe1, // á
0x5c: 0xe9, // é
0x5e: 0xed, // í
0x5f: 0xf3, // ó
0x60: 0xfa, // ú
0x7b: 0xe7, // ç
0x7c: 0xf7, // ÷
0x7d: 0xd1, // Ñ
0x7e: 0xf1, // ñ
0x7f: 0x2588, // █
0x0130: 0xae, // ®
0x0131: 0xb0, // °
0x0132: 0xbd, // ½
0x0133: 0xbf, // ¿
0x0134: 0x2122, // ™
0x0135: 0xa2, // ¢
0x0136: 0xa3, // £
0x0137: 0x266a, // ♪
0x0138: 0xe0, // à
0x0139: 0xa0, //
0x013a: 0xe8, // è
0x013b: 0xe2, // â
0x013c: 0xea, // ê
0x013d: 0xee, // î
0x013e: 0xf4, // ô
0x013f: 0xfb, // û
0x0220: 0xc1, // Á
0x0221: 0xc9, // É
0x0222: 0xd3, // Ó
0x0223: 0xda, // Ú
0x0224: 0xdc, // Ü
0x0225: 0xfc, // ü
0x0226: 0x2018, // ‘
0x0227: 0xa1, // ¡
0x0228: 0x2a, // *
0x0229: 0x27, // '
0x022a: 0x2014, // —
0x022b: 0xa9, // ©
0x022c: 0x2120, // ℠
0x022d: 0x2022, // •
0x022e: 0x201c, // “
0x022f: 0x201d, // ”
0x0230: 0xc0, // À
0x0231: 0xc2, // Â
0x0232: 0xc7, // Ç
0x0233: 0xc8, // È
0x0234: 0xca, // Ê
0x0235: 0xcb, // Ë
0x0236: 0xeb, // ë
0x0237: 0xce, // Î
0x0238: 0xcf, // Ï
0x0239: 0xef, // ï
0x023a: 0xd4, // Ô
0x023b: 0xd9, // Ù
0x023c: 0xf9, // ù
0x023d: 0xdb, // Û
0x023e: 0xab, // «
0x023f: 0xbb, // »
0x0320: 0xc3, // Ã
0x0321: 0xe3, // ã
0x0322: 0xcd, // Í
0x0323: 0xcc, // Ì
0x0324: 0xec, // ì
0x0325: 0xd2, // Ò
0x0326: 0xf2, // ò
0x0327: 0xd5, // Õ
0x0328: 0xf5, // õ
0x0329: 0x7b, // {
0x032a: 0x7d, // }
0x032b: 0x5c, // \
0x032c: 0x5e, // ^
0x032d: 0x5f, // _
0x032e: 0x7c, // |
0x032f: 0x7e, // ~
0x0330: 0xc4, // Ä
0x0331: 0xe4, // ä
0x0332: 0xd6, // Ö
0x0333: 0xf6, // ö
0x0334: 0xdf, // ß
0x0335: 0xa5, // ¥
0x0336: 0xa4, // ¤
0x0337: 0x2502, // │
0x0338: 0xc5, // Å
0x0339: 0xe5, // å
0x033a: 0xd8, // Ø
0x033b: 0xf8, // ø
0x033c: 0x250c, // ┌
0x033d: 0x2510, // ┐
0x033e: 0x2514, // └
0x033f: 0x2518 // ┘
};
var getCharFromCode = function(code) {
if (code === null) {
return '';
}
code = CHARACTER_TRANSLATION[code] || code;
return String.fromCharCode(code);
};
// the index of the last row in a CEA-608 display buffer
var BOTTOM_ROW = 14;
// This array is used for mapping PACs -> row #, since there's no way of
// getting it through bit logic.
var ROWS = [0x1100, 0x1120, 0x1200, 0x1220, 0x1500, 0x1520, 0x1600, 0x1620,
0x1700, 0x1720, 0x1000, 0x1300, 0x1320, 0x1400, 0x1420];
// CEA-608 captions are rendered onto a 34x15 matrix of character
// cells. The "bottom" row is the last element in the outer array.
var createDisplayBuffer = function() {
var result = [], i = BOTTOM_ROW + 1;
while (i--) {
result.push('');
}
return result;
};
var Cea608Stream = function(field, dataChannel) {
Cea608Stream.prototype.init.call(this);
this.field_ = field || 0;
this.dataChannel_ = dataChannel || 0;
this.name_ = 'CC' + (((this.field_ << 1) | this.dataChannel_) + 1);
this.setConstants();
this.reset();
this.push = function(packet) {
var data, swap, char0, char1, text;
// remove the parity bits
data = packet.ccData & 0x7f7f;
// ignore duplicate control codes; the spec demands they're sent twice
if (data === this.lastControlCode_) {
this.lastControlCode_ = null;
return;
}
// Store control codes
if ((data & 0xf000) === 0x1000) {
this.lastControlCode_ = data;
} else if (data !== this.PADDING_) {
this.lastControlCode_ = null;
}
char0 = data >>> 8;
char1 = data & 0xff;
if (data === this.PADDING_) {
return;
} else if (data === this.RESUME_CAPTION_LOADING_) {
this.mode_ = 'popOn';
} else if (data === this.END_OF_CAPTION_) {
this.clearFormatting(packet.pts);
// if a caption was being displayed, it's gone now
this.flushDisplayed(packet.pts);
// flip memory
swap = this.displayed_;
this.displayed_ = this.nonDisplayed_;
this.nonDisplayed_ = swap;
// start measuring the time to display the caption
this.startPts_ = packet.pts;
} else if (data === this.ROLL_UP_2_ROWS_) {
this.topRow_ = BOTTOM_ROW - 1;
this.mode_ = 'rollUp';
} else if (data === this.ROLL_UP_3_ROWS_) {
this.topRow_ = BOTTOM_ROW - 2;
this.mode_ = 'rollUp';
} else if (data === this.ROLL_UP_4_ROWS_) {
this.topRow_ = BOTTOM_ROW - 3;
this.mode_ = 'rollUp';
} else if (data === this.CARRIAGE_RETURN_) {
this.clearFormatting(packet.pts);
this.flushDisplayed(packet.pts);
this.shiftRowsUp_();
this.startPts_ = packet.pts;
} else if (data === this.BACKSPACE_) {
if (this.mode_ === 'popOn') {
this.nonDisplayed_[BOTTOM_ROW] = this.nonDisplayed_[BOTTOM_ROW].slice(0, -1);
} else {
this.displayed_[BOTTOM_ROW] = this.displayed_[BOTTOM_ROW].slice(0, -1);
}
} else if (data === this.ERASE_DISPLAYED_MEMORY_) {
this.flushDisplayed(packet.pts);
this.displayed_ = createDisplayBuffer();
} else if (data === this.ERASE_NON_DISPLAYED_MEMORY_) {
this.nonDisplayed_ = createDisplayBuffer();
} else if (data === this.RESUME_DIRECT_CAPTIONING_) {
this.mode_ = 'paintOn';
// Append special characters to caption text
} else if (this.isSpecialCharacter(char0, char1)) {
// Bitmask char0 so that we can apply character transformations
// regardless of field and data channel.
// Then byte-shift to the left and OR with char1 so we can pass the
// entire character code to `getCharFromCode`.
char0 = (char0 & 0x03) << 8;
text = getCharFromCode(char0 | char1);
this[this.mode_](packet.pts, text);
this.column_++;
// Append extended characters to caption text
} else if (this.isExtCharacter(char0, char1)) {
// Extended characters always follow their "non-extended" equivalents.
// IE if a "è" is desired, you'll always receive "eè"; non-compliant
// decoders are supposed to drop the "è", while compliant decoders
// backspace the "e" and insert "è".
// Delete the previous character
if (this.mode_ === 'popOn') {
this.nonDisplayed_[this.row_] = this.nonDisplayed_[this.row_].slice(0, -1);
} else {
this.displayed_[BOTTOM_ROW] = this.displayed_[BOTTOM_ROW].slice(0, -1);
}
// Bitmask char0 so that we can apply character transformations
// regardless of field and data channel.
// Then byte-shift to the left and OR with char1 so we can pass the
// entire character code to `getCharFromCode`.
char0 = (char0 & 0x03) << 8;
text = getCharFromCode(char0 | char1);
this[this.mode_](packet.pts, text);
this.column_++;
// Process mid-row codes
} else if (this.isMidRowCode(char0, char1)) {
// Attributes are not additive, so clear all formatting
this.clearFormatting(packet.pts);
// According to the standard, mid-row codes
// should be replaced with spaces, so add one now
this[this.mode_](packet.pts, ' ');
this.column_++;
if ((char1 & 0xe) === 0xe) {
this.addFormatting(packet.pts, ['i']);
}
if ((char1 & 0x1) === 0x1) {
this.addFormatting(packet.pts, ['u']);
}
// Detect offset control codes and adjust cursor
} else if (this.isOffsetControlCode(char0, char1)) {
// Cursor position is set by indent PAC (see below) in 4-column
// increments, with an additional offset code of 1-3 to reach any
// of the 32 columns specified by CEA-608. So all we need to do
// here is increment the column cursor by the given offset.
this.column_ += (char1 & 0x03);
// Detect PACs (Preamble Address Codes)
} else if (this.isPAC(char0, char1)) {
// There's no logic for PAC -> row mapping, so we have to just
// find the row code in an array and use its index :(
var row = ROWS.indexOf(data & 0x1f20);
if (row !== this.row_) {
// formatting is only persistent for current row
this.clearFormatting(packet.pts);
this.row_ = row;
}
// All PACs can apply underline, so detect and apply
// (All odd-numbered second bytes set underline)
if ((char1 & 0x1) && (this.formatting_.indexOf('u') === -1)) {
this.addFormatting(packet.pts, ['u']);
}
if ((data & 0x10) === 0x10) {
// We've got an indent level code. Each successive even number
// increments the column cursor by 4, so we can get the desired
// column position by bit-shifting to the right (to get n/2)
// and multiplying by 4.
this.column_ = ((data & 0xe) >> 1) * 4;
}
if (this.isColorPAC(char1)) {
// it's a color code, though we only support white, which
// can be either normal or italicized. white italics can be
// either 0x4e or 0x6e depending on the row, so we just
// bitwise-and with 0xe to see if italics should be turned on
if ((char1 & 0xe) === 0xe) {
this.addFormatting(packet.pts, ['i']);
}
}
// We have a normal character in char0, and possibly one in char1
} else if (this.isNormalChar(char0)) {
if (char1 === 0x00) {
char1 = null;
}
text = getCharFromCode(char0);
text += getCharFromCode(char1);
this[this.mode_](packet.pts, text);
this.column_ += text.length;
} // finish data processing
};
};
Cea608Stream.prototype = new Stream();
// Trigger a cue point that captures the current state of the
// display buffer
Cea608Stream.prototype.flushDisplayed = function(pts) {
var content = this.displayed_
// remove spaces from the start and end of the string
.map(function(row) {
return row.trim();
})
// combine all text rows to display in one cue
.join('\n')
// and remove blank rows from the start and end, but not the middle
.replace(/^\n+|\n+$/g, '');
if (content.length) {
this.trigger('data', {
startPts: this.startPts_,
endPts: pts,
text: content,
stream: this.name_
});
}
};
/**
* Zero out the data, used for startup and on seek
*/
Cea608Stream.prototype.reset = function() {
this.mode_ = 'popOn';
// When in roll-up mode, the index of the last row that will
// actually display captions. If a caption is shifted to a row
// with a lower index than this, it is cleared from the display
// buffer
this.topRow_ = 0;
this.startPts_ = 0;
this.displayed_ = createDisplayBuffer();
this.nonDisplayed_ = createDisplayBuffer();
this.lastControlCode_ = null;
// Track row and column for proper line-breaking and spacing
this.column_ = 0;
this.row_ = BOTTOM_ROW;
// This variable holds currently-applied formatting
this.formatting_ = [];
};
/**
* Sets up control code and related constants for this instance
*/
Cea608Stream.prototype.setConstants = function() {
// The following attributes have these uses:
// ext_ : char0 for mid-row codes, and the base for extended
// chars (ext_+0, ext_+1, and ext_+2 are char0s for
// extended codes)
// control_: char0 for control codes, except byte-shifted to the
// left so that we can do this.control_ | CONTROL_CODE
// offset_: char0 for tab offset codes
//
// It's also worth noting that control codes, and _only_ control codes,
// differ between field 1 and field2. Field 2 control codes are always
// their field 1 value plus 1. That's why there's the "| field" on the
// control value.
if (this.dataChannel_ === 0) {
this.BASE_ = 0x10;
this.EXT_ = 0x11;
this.CONTROL_ = (0x14 | this.field_) << 8;
this.OFFSET_ = 0x17;
} else if (this.dataChannel_ === 1) {
this.BASE_ = 0x18;
this.EXT_ = 0x19;
this.CONTROL_ = (0x1c | this.field_) << 8;
this.OFFSET_ = 0x1f;
}
// Constants for the LSByte command codes recognized by Cea608Stream. This
// list is not exhaustive. For a more comprehensive listing and semantics see
// http://www.gpo.gov/fdsys/pkg/CFR-2010-title47-vol1/pdf/CFR-2010-title47-vol1-sec15-119.pdf
// Padding
this.PADDING_ = 0x0000;
// Pop-on Mode
this.RESUME_CAPTION_LOADING_ = this.CONTROL_ | 0x20;
this.END_OF_CAPTION_ = this.CONTROL_ | 0x2f;
// Roll-up Mode
this.ROLL_UP_2_ROWS_ = this.CONTROL_ | 0x25;
this.ROLL_UP_3_ROWS_ = this.CONTROL_ | 0x26;
this.ROLL_UP_4_ROWS_ = this.CONTROL_ | 0x27;
this.CARRIAGE_RETURN_ = this.CONTROL_ | 0x2d;
// paint-on mode (not supported)
this.RESUME_DIRECT_CAPTIONING_ = this.CONTROL_ | 0x29;
// Erasure
this.BACKSPACE_ = this.CONTROL_ | 0x21;
this.ERASE_DISPLAYED_MEMORY_ = this.CONTROL_ | 0x2c;
this.ERASE_NON_DISPLAYED_MEMORY_ = this.CONTROL_ | 0x2e;
};
/**
* Detects if the 2-byte packet data is a special character
*
* Special characters have a second byte in the range 0x30 to 0x3f,
* with the first byte being 0x11 (for data channel 1) or 0x19 (for
* data channel 2).
*
* @param {Integer} char0 The first byte
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the 2 bytes are an special character
*/
Cea608Stream.prototype.isSpecialCharacter = function(char0, char1) {
return (char0 === this.EXT_ && char1 >= 0x30 && char1 <= 0x3f);
};
/**
* Detects if the 2-byte packet data is an extended character
*
* Extended characters have a second byte in the range 0x20 to 0x3f,
* with the first byte being 0x12 or 0x13 (for data channel 1) or
* 0x1a or 0x1b (for data channel 2).
*
* @param {Integer} char0 The first byte
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the 2 bytes are an extended character
*/
Cea608Stream.prototype.isExtCharacter = function(char0, char1) {
return ((char0 === (this.EXT_ + 1) || char0 === (this.EXT_ + 2)) &&
(char1 >= 0x20 && char1 <= 0x3f));
};
/**
* Detects if the 2-byte packet is a mid-row code
*
* Mid-row codes have a second byte in the range 0x20 to 0x2f, with
* the first byte being 0x11 (for data channel 1) or 0x19 (for data
* channel 2).
*
* @param {Integer} char0 The first byte
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the 2 bytes are a mid-row code
*/
Cea608Stream.prototype.isMidRowCode = function(char0, char1) {
return (char0 === this.EXT_ && (char1 >= 0x20 && char1 <= 0x2f));
};
/**
* Detects if the 2-byte packet is an offset control code
*
* Offset control codes have a second byte in the range 0x21 to 0x23,
* with the first byte being 0x17 (for data channel 1) or 0x1f (for
* data channel 2).
*
* @param {Integer} char0 The first byte
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the 2 bytes are an offset control code
*/
Cea608Stream.prototype.isOffsetControlCode = function(char0, char1) {
return (char0 === this.OFFSET_ && (char1 >= 0x21 && char1 <= 0x23));
};
/**
* Detects if the 2-byte packet is a Preamble Address Code
*
* PACs have a first byte in the range 0x10 to 0x17 (for data channel 1)
* or 0x18 to 0x1f (for data channel 2), with the second byte in the
* range 0x40 to 0x7f.
*
* @param {Integer} char0 The first byte
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the 2 bytes are a PAC
*/
Cea608Stream.prototype.isPAC = function(char0, char1) {
return (char0 >= this.BASE_ && char0 < (this.BASE_ + 8) &&
(char1 >= 0x40 && char1 <= 0x7f));
};
/**
* Detects if a packet's second byte is in the range of a PAC color code
*
* PAC color codes have the second byte be in the range 0x40 to 0x4f, or
* 0x60 to 0x6f.
*
* @param {Integer} char1 The second byte
* @return {Boolean} Whether the byte is a color PAC
*/
Cea608Stream.prototype.isColorPAC = function(char1) {
return ((char1 >= 0x40 && char1 <= 0x4f) || (char1 >= 0x60 && char1 <= 0x7f));
};
/**
* Detects if a single byte is in the range of a normal character
*
* Normal text bytes are in the range 0x20 to 0x7f.
*
* @param {Integer} char The byte
* @return {Boolean} Whether the byte is a normal character
*/
Cea608Stream.prototype.isNormalChar = function(char) {
return (char >= 0x20 && char <= 0x7f);
};
// Adds the opening HTML tag for the passed character to the caption text,
// and keeps track of it for later closing
Cea608Stream.prototype.addFormatting = function(pts, format) {
this.formatting_ = this.formatting_.concat(format);
var text = format.reduce(function(text, format) {
return text + '<' + format + '>';
}, '');
this[this.mode_](pts, text);
};
// Adds HTML closing tags for current formatting to caption text and
// clears remembered formatting
Cea608Stream.prototype.clearFormatting = function(pts) {
if (!this.formatting_.length) {
return;
}
var text = this.formatting_.reverse().reduce(function(text, format) {
return text + '</' + format + '>';
}, '');
this.formatting_ = [];
this[this.mode_](pts, text);
};
// Mode Implementations
Cea608Stream.prototype.popOn = function(pts, text) {
var baseRow = this.nonDisplayed_[this.row_];
// buffer characters
baseRow += text;
this.nonDisplayed_[this.row_] = baseRow;
};
Cea608Stream.prototype.rollUp = function(pts, text) {
var baseRow = this.displayed_[BOTTOM_ROW];
baseRow += text;
this.displayed_[BOTTOM_ROW] = baseRow;
};
Cea608Stream.prototype.shiftRowsUp_ = function() {
var i;
// clear out inactive rows
for (i = 0; i < this.topRow_; i++) {