track-decode-info.js
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"use strict";
/**
* mux.js
*
* Copyright (c) Brightcove
* Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
*/
var ONE_SECOND_IN_TS = require('../utils/clock').ONE_SECOND_IN_TS;
/**
* Store information about the start and end of the track and the
* duration for each frame/sample we process in order to calculate
* the baseMediaDecodeTime
*/
var collectDtsInfo = function collectDtsInfo(track, data) {
if (typeof data.pts === 'number') {
if (track.timelineStartInfo.pts === undefined) {
track.timelineStartInfo.pts = data.pts;
}
if (track.minSegmentPts === undefined) {
track.minSegmentPts = data.pts;
} else {
track.minSegmentPts = Math.min(track.minSegmentPts, data.pts);
}
if (track.maxSegmentPts === undefined) {
track.maxSegmentPts = data.pts;
} else {
track.maxSegmentPts = Math.max(track.maxSegmentPts, data.pts);
}
}
if (typeof data.dts === 'number') {
if (track.timelineStartInfo.dts === undefined) {
track.timelineStartInfo.dts = data.dts;
}
if (track.minSegmentDts === undefined) {
track.minSegmentDts = data.dts;
} else {
track.minSegmentDts = Math.min(track.minSegmentDts, data.dts);
}
if (track.maxSegmentDts === undefined) {
track.maxSegmentDts = data.dts;
} else {
track.maxSegmentDts = Math.max(track.maxSegmentDts, data.dts);
}
}
};
/**
* Clear values used to calculate the baseMediaDecodeTime between
* tracks
*/
var clearDtsInfo = function clearDtsInfo(track) {
delete track.minSegmentDts;
delete track.maxSegmentDts;
delete track.minSegmentPts;
delete track.maxSegmentPts;
};
/**
* Calculate the track's baseMediaDecodeTime based on the earliest
* DTS the transmuxer has ever seen and the minimum DTS for the
* current track
* @param track {object} track metadata configuration
* @param keepOriginalTimestamps {boolean} If true, keep the timestamps
* in the source; false to adjust the first segment to start at 0.
*/
var calculateTrackBaseMediaDecodeTime = function calculateTrackBaseMediaDecodeTime(track, keepOriginalTimestamps) {
var baseMediaDecodeTime,
scale,
minSegmentDts = track.minSegmentDts; // Optionally adjust the time so the first segment starts at zero.
if (!keepOriginalTimestamps) {
minSegmentDts -= track.timelineStartInfo.dts;
} // track.timelineStartInfo.baseMediaDecodeTime is the location, in time, where
// we want the start of the first segment to be placed
baseMediaDecodeTime = track.timelineStartInfo.baseMediaDecodeTime; // Add to that the distance this segment is from the very first
baseMediaDecodeTime += minSegmentDts; // baseMediaDecodeTime must not become negative
baseMediaDecodeTime = Math.max(0, baseMediaDecodeTime);
if (track.type === 'audio') {
// Audio has a different clock equal to the sampling_rate so we need to
// scale the PTS values into the clock rate of the track
scale = track.samplerate / ONE_SECOND_IN_TS;
baseMediaDecodeTime *= scale;
baseMediaDecodeTime = Math.floor(baseMediaDecodeTime);
}
return baseMediaDecodeTime;
};
module.exports = {
clearDtsInfo: clearDtsInfo,
calculateTrackBaseMediaDecodeTime: calculateTrackBaseMediaDecodeTime,
collectDtsInfo: collectDtsInfo
};