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535 lines
17 KiB
535 lines
17 KiB
/**
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* mux.js
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*
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* Copyright (c) Brightcove
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* Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
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*
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* A stream-based mp2t to mp4 converter. This utility can be used to
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* deliver mp4s to a SourceBuffer on platforms that support native
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* Media Source Extensions.
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*/
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'use strict';
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var Stream = require('../utils/stream.js'),
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CaptionStream = require('./caption-stream'),
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StreamTypes = require('./stream-types'),
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TimestampRolloverStream = require('./timestamp-rollover-stream').TimestampRolloverStream; // object types
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var _TransportPacketStream, _TransportParseStream, _ElementaryStream; // constants
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var MP2T_PACKET_LENGTH = 188,
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// bytes
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SYNC_BYTE = 0x47;
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/**
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* Splits an incoming stream of binary data into MPEG-2 Transport
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* Stream packets.
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*/
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_TransportPacketStream = function TransportPacketStream() {
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var buffer = new Uint8Array(MP2T_PACKET_LENGTH),
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bytesInBuffer = 0;
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_TransportPacketStream.prototype.init.call(this); // Deliver new bytes to the stream.
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/**
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* Split a stream of data into M2TS packets
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**/
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this.push = function (bytes) {
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var startIndex = 0,
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endIndex = MP2T_PACKET_LENGTH,
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everything; // If there are bytes remaining from the last segment, prepend them to the
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// bytes that were pushed in
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if (bytesInBuffer) {
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everything = new Uint8Array(bytes.byteLength + bytesInBuffer);
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everything.set(buffer.subarray(0, bytesInBuffer));
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everything.set(bytes, bytesInBuffer);
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bytesInBuffer = 0;
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} else {
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everything = bytes;
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} // While we have enough data for a packet
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while (endIndex < everything.byteLength) {
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// Look for a pair of start and end sync bytes in the data..
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if (everything[startIndex] === SYNC_BYTE && everything[endIndex] === SYNC_BYTE) {
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// We found a packet so emit it and jump one whole packet forward in
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// the stream
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this.trigger('data', everything.subarray(startIndex, endIndex));
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startIndex += MP2T_PACKET_LENGTH;
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endIndex += MP2T_PACKET_LENGTH;
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continue;
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} // If we get here, we have somehow become de-synchronized and we need to step
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// forward one byte at a time until we find a pair of sync bytes that denote
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// a packet
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startIndex++;
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endIndex++;
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} // If there was some data left over at the end of the segment that couldn't
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// possibly be a whole packet, keep it because it might be the start of a packet
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// that continues in the next segment
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if (startIndex < everything.byteLength) {
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buffer.set(everything.subarray(startIndex), 0);
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bytesInBuffer = everything.byteLength - startIndex;
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}
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};
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/**
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* Passes identified M2TS packets to the TransportParseStream to be parsed
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**/
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this.flush = function () {
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// If the buffer contains a whole packet when we are being flushed, emit it
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// and empty the buffer. Otherwise hold onto the data because it may be
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// important for decoding the next segment
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if (bytesInBuffer === MP2T_PACKET_LENGTH && buffer[0] === SYNC_BYTE) {
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this.trigger('data', buffer);
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bytesInBuffer = 0;
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}
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this.trigger('done');
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};
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this.endTimeline = function () {
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this.flush();
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this.trigger('endedtimeline');
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};
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this.reset = function () {
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bytesInBuffer = 0;
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this.trigger('reset');
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};
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};
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_TransportPacketStream.prototype = new Stream();
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/**
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* Accepts an MP2T TransportPacketStream and emits data events with parsed
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* forms of the individual transport stream packets.
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*/
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_TransportParseStream = function TransportParseStream() {
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var parsePsi, parsePat, parsePmt, self;
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_TransportParseStream.prototype.init.call(this);
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self = this;
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this.packetsWaitingForPmt = [];
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this.programMapTable = undefined;
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parsePsi = function parsePsi(payload, psi) {
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var offset = 0; // PSI packets may be split into multiple sections and those
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// sections may be split into multiple packets. If a PSI
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// section starts in this packet, the payload_unit_start_indicator
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// will be true and the first byte of the payload will indicate
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// the offset from the current position to the start of the
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// section.
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if (psi.payloadUnitStartIndicator) {
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offset += payload[offset] + 1;
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}
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if (psi.type === 'pat') {
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parsePat(payload.subarray(offset), psi);
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} else {
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parsePmt(payload.subarray(offset), psi);
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}
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};
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parsePat = function parsePat(payload, pat) {
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pat.section_number = payload[7]; // eslint-disable-line camelcase
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pat.last_section_number = payload[8]; // eslint-disable-line camelcase
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// skip the PSI header and parse the first PMT entry
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self.pmtPid = (payload[10] & 0x1F) << 8 | payload[11];
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pat.pmtPid = self.pmtPid;
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};
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/**
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* Parse out the relevant fields of a Program Map Table (PMT).
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* @param payload {Uint8Array} the PMT-specific portion of an MP2T
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* packet. The first byte in this array should be the table_id
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* field.
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* @param pmt {object} the object that should be decorated with
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* fields parsed from the PMT.
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*/
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parsePmt = function parsePmt(payload, pmt) {
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var sectionLength, tableEnd, programInfoLength, offset; // PMTs can be sent ahead of the time when they should actually
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// take effect. We don't believe this should ever be the case
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// for HLS but we'll ignore "forward" PMT declarations if we see
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// them. Future PMT declarations have the current_next_indicator
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// set to zero.
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if (!(payload[5] & 0x01)) {
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return;
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} // overwrite any existing program map table
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self.programMapTable = {
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video: null,
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audio: null,
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'timed-metadata': {}
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}; // the mapping table ends at the end of the current section
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sectionLength = (payload[1] & 0x0f) << 8 | payload[2];
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tableEnd = 3 + sectionLength - 4; // to determine where the table is, we have to figure out how
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// long the program info descriptors are
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programInfoLength = (payload[10] & 0x0f) << 8 | payload[11]; // advance the offset to the first entry in the mapping table
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offset = 12 + programInfoLength;
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while (offset < tableEnd) {
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var streamType = payload[offset];
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var pid = (payload[offset + 1] & 0x1F) << 8 | payload[offset + 2]; // only map a single elementary_pid for audio and video stream types
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// TODO: should this be done for metadata too? for now maintain behavior of
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// multiple metadata streams
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if (streamType === StreamTypes.H264_STREAM_TYPE && self.programMapTable.video === null) {
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self.programMapTable.video = pid;
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} else if (streamType === StreamTypes.ADTS_STREAM_TYPE && self.programMapTable.audio === null) {
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self.programMapTable.audio = pid;
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} else if (streamType === StreamTypes.METADATA_STREAM_TYPE) {
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// map pid to stream type for metadata streams
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self.programMapTable['timed-metadata'][pid] = streamType;
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} // move to the next table entry
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// skip past the elementary stream descriptors, if present
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offset += ((payload[offset + 3] & 0x0F) << 8 | payload[offset + 4]) + 5;
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} // record the map on the packet as well
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pmt.programMapTable = self.programMapTable;
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};
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/**
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* Deliver a new MP2T packet to the next stream in the pipeline.
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*/
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this.push = function (packet) {
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var result = {},
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offset = 4;
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result.payloadUnitStartIndicator = !!(packet[1] & 0x40); // pid is a 13-bit field starting at the last bit of packet[1]
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result.pid = packet[1] & 0x1f;
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result.pid <<= 8;
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result.pid |= packet[2]; // if an adaption field is present, its length is specified by the
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// fifth byte of the TS packet header. The adaptation field is
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// used to add stuffing to PES packets that don't fill a complete
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// TS packet, and to specify some forms of timing and control data
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// that we do not currently use.
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if ((packet[3] & 0x30) >>> 4 > 0x01) {
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offset += packet[offset] + 1;
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} // parse the rest of the packet based on the type
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if (result.pid === 0) {
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result.type = 'pat';
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parsePsi(packet.subarray(offset), result);
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this.trigger('data', result);
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} else if (result.pid === this.pmtPid) {
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result.type = 'pmt';
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parsePsi(packet.subarray(offset), result);
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this.trigger('data', result); // if there are any packets waiting for a PMT to be found, process them now
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while (this.packetsWaitingForPmt.length) {
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this.processPes_.apply(this, this.packetsWaitingForPmt.shift());
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}
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} else if (this.programMapTable === undefined) {
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// When we have not seen a PMT yet, defer further processing of
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// PES packets until one has been parsed
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this.packetsWaitingForPmt.push([packet, offset, result]);
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} else {
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this.processPes_(packet, offset, result);
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}
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};
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this.processPes_ = function (packet, offset, result) {
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// set the appropriate stream type
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if (result.pid === this.programMapTable.video) {
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result.streamType = StreamTypes.H264_STREAM_TYPE;
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} else if (result.pid === this.programMapTable.audio) {
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result.streamType = StreamTypes.ADTS_STREAM_TYPE;
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} else {
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// if not video or audio, it is timed-metadata or unknown
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// if unknown, streamType will be undefined
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result.streamType = this.programMapTable['timed-metadata'][result.pid];
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}
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result.type = 'pes';
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result.data = packet.subarray(offset);
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this.trigger('data', result);
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};
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};
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_TransportParseStream.prototype = new Stream();
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_TransportParseStream.STREAM_TYPES = {
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h264: 0x1b,
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adts: 0x0f
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};
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/**
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* Reconsistutes program elementary stream (PES) packets from parsed
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* transport stream packets. That is, if you pipe an
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* mp2t.TransportParseStream into a mp2t.ElementaryStream, the output
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* events will be events which capture the bytes for individual PES
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* packets plus relevant metadata that has been extracted from the
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* container.
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*/
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_ElementaryStream = function ElementaryStream() {
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var self = this,
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// PES packet fragments
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video = {
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data: [],
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size: 0
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},
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audio = {
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data: [],
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size: 0
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},
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timedMetadata = {
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data: [],
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size: 0
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},
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programMapTable,
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parsePes = function parsePes(payload, pes) {
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var ptsDtsFlags;
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var startPrefix = payload[0] << 16 | payload[1] << 8 | payload[2]; // default to an empty array
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pes.data = new Uint8Array(); // In certain live streams, the start of a TS fragment has ts packets
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// that are frame data that is continuing from the previous fragment. This
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// is to check that the pes data is the start of a new pes payload
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if (startPrefix !== 1) {
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return;
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} // get the packet length, this will be 0 for video
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pes.packetLength = 6 + (payload[4] << 8 | payload[5]); // find out if this packets starts a new keyframe
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pes.dataAlignmentIndicator = (payload[6] & 0x04) !== 0; // PES packets may be annotated with a PTS value, or a PTS value
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// and a DTS value. Determine what combination of values is
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// available to work with.
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ptsDtsFlags = payload[7]; // PTS and DTS are normally stored as a 33-bit number. Javascript
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// performs all bitwise operations on 32-bit integers but javascript
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// supports a much greater range (52-bits) of integer using standard
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// mathematical operations.
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// We construct a 31-bit value using bitwise operators over the 31
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// most significant bits and then multiply by 4 (equal to a left-shift
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// of 2) before we add the final 2 least significant bits of the
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// timestamp (equal to an OR.)
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if (ptsDtsFlags & 0xC0) {
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// the PTS and DTS are not written out directly. For information
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// on how they are encoded, see
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// http://dvd.sourceforge.net/dvdinfo/pes-hdr.html
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pes.pts = (payload[9] & 0x0E) << 27 | (payload[10] & 0xFF) << 20 | (payload[11] & 0xFE) << 12 | (payload[12] & 0xFF) << 5 | (payload[13] & 0xFE) >>> 3;
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pes.pts *= 4; // Left shift by 2
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pes.pts += (payload[13] & 0x06) >>> 1; // OR by the two LSBs
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pes.dts = pes.pts;
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if (ptsDtsFlags & 0x40) {
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pes.dts = (payload[14] & 0x0E) << 27 | (payload[15] & 0xFF) << 20 | (payload[16] & 0xFE) << 12 | (payload[17] & 0xFF) << 5 | (payload[18] & 0xFE) >>> 3;
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pes.dts *= 4; // Left shift by 2
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pes.dts += (payload[18] & 0x06) >>> 1; // OR by the two LSBs
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}
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} // the data section starts immediately after the PES header.
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// pes_header_data_length specifies the number of header bytes
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// that follow the last byte of the field.
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pes.data = payload.subarray(9 + payload[8]);
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},
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/**
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* Pass completely parsed PES packets to the next stream in the pipeline
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**/
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flushStream = function flushStream(stream, type, forceFlush) {
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var packetData = new Uint8Array(stream.size),
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event = {
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type: type
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},
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i = 0,
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offset = 0,
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packetFlushable = false,
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fragment; // do nothing if there is not enough buffered data for a complete
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// PES header
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if (!stream.data.length || stream.size < 9) {
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return;
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}
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event.trackId = stream.data[0].pid; // reassemble the packet
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for (i = 0; i < stream.data.length; i++) {
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fragment = stream.data[i];
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packetData.set(fragment.data, offset);
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offset += fragment.data.byteLength;
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} // parse assembled packet's PES header
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parsePes(packetData, event); // non-video PES packets MUST have a non-zero PES_packet_length
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// check that there is enough stream data to fill the packet
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packetFlushable = type === 'video' || event.packetLength <= stream.size; // flush pending packets if the conditions are right
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if (forceFlush || packetFlushable) {
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stream.size = 0;
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stream.data.length = 0;
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} // only emit packets that are complete. this is to avoid assembling
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// incomplete PES packets due to poor segmentation
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if (packetFlushable) {
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self.trigger('data', event);
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}
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};
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_ElementaryStream.prototype.init.call(this);
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/**
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* Identifies M2TS packet types and parses PES packets using metadata
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* parsed from the PMT
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**/
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this.push = function (data) {
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({
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pat: function pat() {// we have to wait for the PMT to arrive as well before we
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// have any meaningful metadata
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},
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pes: function pes() {
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var stream, streamType;
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switch (data.streamType) {
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case StreamTypes.H264_STREAM_TYPE:
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stream = video;
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streamType = 'video';
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break;
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case StreamTypes.ADTS_STREAM_TYPE:
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stream = audio;
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streamType = 'audio';
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break;
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case StreamTypes.METADATA_STREAM_TYPE:
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stream = timedMetadata;
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streamType = 'timed-metadata';
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break;
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default:
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// ignore unknown stream types
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return;
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} // if a new packet is starting, we can flush the completed
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// packet
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if (data.payloadUnitStartIndicator) {
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flushStream(stream, streamType, true);
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} // buffer this fragment until we are sure we've received the
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// complete payload
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stream.data.push(data);
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stream.size += data.data.byteLength;
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},
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pmt: function pmt() {
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var event = {
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type: 'metadata',
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tracks: []
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};
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programMapTable = data.programMapTable; // translate audio and video streams to tracks
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if (programMapTable.video !== null) {
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event.tracks.push({
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timelineStartInfo: {
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baseMediaDecodeTime: 0
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},
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id: +programMapTable.video,
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codec: 'avc',
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type: 'video'
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});
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}
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if (programMapTable.audio !== null) {
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event.tracks.push({
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timelineStartInfo: {
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baseMediaDecodeTime: 0
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},
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id: +programMapTable.audio,
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codec: 'adts',
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type: 'audio'
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});
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}
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self.trigger('data', event);
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}
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})[data.type]();
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};
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this.reset = function () {
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video.size = 0;
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video.data.length = 0;
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audio.size = 0;
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audio.data.length = 0;
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this.trigger('reset');
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};
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/**
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* Flush any remaining input. Video PES packets may be of variable
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* length. Normally, the start of a new video packet can trigger the
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* finalization of the previous packet. That is not possible if no
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* more video is forthcoming, however. In that case, some other
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* mechanism (like the end of the file) has to be employed. When it is
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* clear that no additional data is forthcoming, calling this method
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* will flush the buffered packets.
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*/
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this.flushStreams_ = function () {
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// !!THIS ORDER IS IMPORTANT!!
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// video first then audio
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flushStream(video, 'video');
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flushStream(audio, 'audio');
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flushStream(timedMetadata, 'timed-metadata');
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};
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this.flush = function () {
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this.flushStreams_();
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this.trigger('done');
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};
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};
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_ElementaryStream.prototype = new Stream();
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var m2ts = {
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PAT_PID: 0x0000,
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MP2T_PACKET_LENGTH: MP2T_PACKET_LENGTH,
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TransportPacketStream: _TransportPacketStream,
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TransportParseStream: _TransportParseStream,
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ElementaryStream: _ElementaryStream,
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TimestampRolloverStream: TimestampRolloverStream,
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CaptionStream: CaptionStream.CaptionStream,
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Cea608Stream: CaptionStream.Cea608Stream,
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Cea708Stream: CaptionStream.Cea708Stream,
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MetadataStream: require('./metadata-stream')
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};
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|
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for (var type in StreamTypes) {
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if (StreamTypes.hasOwnProperty(type)) {
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m2ts[type] = StreamTypes[type];
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|
}
|
|
}
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|
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module.exports = m2ts; |