shaka-player
Version:
DASH/EME video player library
308 lines (263 loc) • 8.21 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.cea.CeaUtils');
goog.provide('shaka.cea.CeaUtils.StyledChar');
goog.require('shaka.text.Cue');
shaka.cea.CeaUtils = class {
/**
* Emits a closed caption based on the state of the buffer.
* @param {!shaka.text.Cue} topLevelCue
* @param {string} stream
* @param {!Array<!Array<?shaka.cea.CeaUtils.StyledChar>>} memory
* @param {number} startTime Start time of the cue.
* @param {number} endTime End time of the cue.
* @return {?shaka.extern.ICaptionDecoder.ClosedCaption}
*/
static getParsedCaption(topLevelCue, stream, memory, startTime, endTime) {
if (startTime >= endTime) {
return null;
}
// Find the first and last row that contains characters.
let firstNonEmptyRow = -1;
let lastNonEmptyRow = -1;
for (let i = 0; i < memory.length; i++) {
if (memory[i].some((e) => e != null && e.getChar().trim() != '')) {
firstNonEmptyRow = i;
break;
}
}
for (let i = memory.length - 1; i >= 0; i--) {
if (memory[i].some((e) => e != null && e.getChar().trim() != '')) {
lastNonEmptyRow = i;
break;
}
}
// Exit early if no non-empty row was found.
if (firstNonEmptyRow === -1 || lastNonEmptyRow === -1) {
return null;
}
// Keeps track of the current styles for a cue being emitted.
let currentUnderline = false;
let currentItalics = false;
let currentTextColor = shaka.cea.CeaUtils.DEFAULT_TXT_COLOR;
let currentBackgroundColor = shaka.cea.CeaUtils.DEFAULT_BG_COLOR;
// Create first cue that will be nested in top level cue. Default styles.
let currentCue = shaka.cea.CeaUtils.createStyledCue(
startTime, endTime, currentUnderline, currentItalics,
currentTextColor, currentBackgroundColor);
// Logic: Reduce rows into a single top level cue containing nested cues.
// Each nested cue corresponds either a style change or a line break.
for (let i = firstNonEmptyRow; i <= lastNonEmptyRow; i++) {
// Find the first and last non-empty characters in this row. We do this so
// no styles creep in before/after the first and last non-empty chars.
const row = memory[i];
let firstNonEmptyCol = -1;
let lastNonEmptyCol = -1;
for (let j = 0; j < row.length; j++) {
if (row[j] != null && row[j].getChar().trim() !== '') {
firstNonEmptyCol = j;
break;
}
}
for (let j = row.length - 1; j >= 0; j--) {
if (row[j] != null && row[j].getChar().trim() !== '') {
lastNonEmptyCol = j;
break;
}
}
// If no non-empty char. was found in this row, it must be a linebreak.
if (firstNonEmptyCol === -1 || lastNonEmptyCol === -1) {
const linebreakCue = shaka.cea.CeaUtils
.createLineBreakCue(startTime, endTime);
topLevelCue.nestedCues.push(linebreakCue);
continue;
}
for (let j = firstNonEmptyCol; j <= lastNonEmptyCol; j++) {
const styledChar = row[j];
// A null between non-empty cells in a row is handled as a space.
if (!styledChar) {
currentCue.payload += ' ';
continue;
}
const underline = styledChar.isUnderlined();
const italics = styledChar.isItalicized();
const textColor = styledChar.getTextColor();
const backgroundColor = styledChar.getBackgroundColor();
// If any style properties have changed, we need to open a new cue.
if (underline != currentUnderline || italics != currentItalics ||
textColor != currentTextColor ||
backgroundColor != currentBackgroundColor) {
// Push the currently built cue and start a new cue, with new styles.
if (currentCue.payload) {
topLevelCue.nestedCues.push(currentCue);
}
currentCue = shaka.cea.CeaUtils.createStyledCue(
startTime, endTime, underline,
italics, textColor, backgroundColor);
currentUnderline = underline;
currentItalics = italics;
currentTextColor = textColor;
currentBackgroundColor = backgroundColor;
}
currentCue.payload += styledChar.getChar();
}
if (currentCue.payload) {
topLevelCue.nestedCues.push(currentCue);
}
// Add a linebreak since the row just ended.
if (i !== lastNonEmptyRow) {
const linebreakCue = shaka.cea.CeaUtils
.createLineBreakCue(startTime, endTime);
topLevelCue.nestedCues.push(linebreakCue);
}
// Create a new cue.
currentCue = shaka.cea.CeaUtils.createStyledCue(
startTime, endTime, currentUnderline, currentItalics,
currentTextColor, currentBackgroundColor);
}
if (topLevelCue.nestedCues.length) {
return {
cue: topLevelCue,
stream,
};
}
return null;
}
/**
* @param {number} startTime
* @param {number} endTime
* @param {boolean} underline
* @param {boolean} italics
* @param {string} txtColor
* @param {string} bgColor
* @return {!shaka.text.Cue}
*/
static createStyledCue(startTime, endTime, underline,
italics, txtColor, bgColor) {
const cue = new shaka.text.Cue(startTime, endTime, /* payload= */ '');
if (underline) {
cue.textDecoration.push(shaka.text.Cue.textDecoration.UNDERLINE);
}
if (italics) {
cue.fontStyle = shaka.text.Cue.fontStyle.ITALIC;
}
cue.color = txtColor;
cue.backgroundColor = bgColor;
return cue;
}
/**
* @param {number} startTime
* @param {number} endTime
* @return {!shaka.text.Cue}
*/
static createLineBreakCue(startTime, endTime) {
const linebreakCue = new shaka.text.Cue(
startTime, endTime, /* payload= */ '');
linebreakCue.lineBreak = true;
return linebreakCue;
}
};
shaka.cea.CeaUtils.StyledChar = class {
/**
* @param {string} character
* @param {boolean} underline
* @param {boolean} italics
* @param {string} backgroundColor
* @param {string} textColor
*/
constructor(character, underline, italics, backgroundColor, textColor) {
/**
* @private {string}
*/
this.character_ = character;
/**
* @private {boolean}
*/
this.underline_ = underline;
/**
* @private {boolean}
*/
this.italics_ = italics;
/**
* @private {string}
*/
this.backgroundColor_ = backgroundColor;
/**
* @private {string}
*/
this.textColor_ = textColor;
}
/**
* @return {string}
*/
getChar() {
return this.character_;
}
/**
* @return {boolean}
*/
isUnderlined() {
return this.underline_;
}
/**
* @return {boolean}
*/
isItalicized() {
return this.italics_;
}
/**
* @return {string}
*/
getBackgroundColor() {
return this.backgroundColor_;
}
/**
* @return {string}
*/
getTextColor() {
return this.textColor_;
}
};
/**
* Default background color for text.
* @const {string}
*/
shaka.cea.CeaUtils.DEFAULT_BG_COLOR = 'black';
/**
* Default text color.
* @const {string}
*/
shaka.cea.CeaUtils.DEFAULT_TXT_COLOR = 'white';
/**
* NALU type for Supplemental Enhancement Information (SEI) for H.264.
* @const {number}
*/
shaka.cea.CeaUtils.H264_NALU_TYPE_SEI = 0x06;
/**
* NALU type for Supplemental Enhancement Information (SEI) for H.265.
* @const {number}
*/
shaka.cea.CeaUtils.H265_PREFIX_NALU_TYPE_SEI = 0x27;
/**
* NALU type for Supplemental Enhancement Information (SEI) for H.265.
* @const {number}
*/
shaka.cea.CeaUtils.H265_SUFFIX_NALU_TYPE_SEI = 0x28;
/**
* NALU type for Supplemental Enhancement Information (SEI) for H.266.
* @const {number}
*/
shaka.cea.CeaUtils.H266_PREFIX_NALU_TYPE_SEI = 0x17;
/**
* NALU type for Supplemental Enhancement Information (SEI) for H.266.
* @const {number}
*/
shaka.cea.CeaUtils.H266_SUFFIX_NALU_TYPE_SEI = 0x18;
/**
* Default timescale value for a track.
* @const {number}
*/
shaka.cea.CeaUtils.DEFAULT_TIMESCALE_VALUE = 90000;