Craig Rowe
97 linhas
3.1 KiB
JavaScript
97 linhas
3.1 KiB
JavaScript
// The AR Drone 2.0 allows a tcp client to receive H264 (MPEG4.10 AVC) video
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// from the drone. However, the frames are wrapped by Parrot Video
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// Encapsulation (PaVE), which this class parses.
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var util = require('util');
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var Stream = require('stream').Stream;
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var buffy = require('buffy');
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module.exports = PaVEParser;
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util.inherits(PaVEParser, Stream);
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function PaVEParser() {
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Stream.call(this);
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this.writable = true;
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this.readable = true;
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this._parser = buffy.createReader();
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this._state = 'header';
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this._frame = undefined;
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}
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PaVEParser.HEADER_SIZE_SHORT = 64;
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PaVEParser.HEADER_SIZE_LONG = 68;
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PaVEParser.prototype.write = function(buffer) {
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var parser = this._parser;
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parser.write(buffer);
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while (true) {
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switch (this._state) {
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case 'header':
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if (parser.bytesAhead() < PaVEParser.HEADER_SIZE_LONG) {
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return;
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}
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this._frame = {
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signature : parser.ascii(4),
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version : parser.uint8(),
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video_codec : parser.uint8(),
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header_size : parser.uint16LE(),
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payload_size : parser.uint32LE(),
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encoded_stream_width : parser.uint16LE(),
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encoded_stream_height : parser.uint16LE(),
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display_width : parser.uint16LE(),
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display_height : parser.uint16LE(),
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frame_number : parser.uint32LE(),
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timestamp : parser.uint32LE(),
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total_chunks : parser.uint8(),
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chunk_index : parser.uint8(),
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frame_type : parser.uint8(),
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control : parser.uint8(),
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stream_byte_position_lw : parser.uint32LE(),
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stream_byte_position_uw : parser.uint32LE(),
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stream_id : parser.uint16LE(),
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total_slices : parser.uint8(),
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slice_index : parser.uint8(),
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header1_size : parser.uint8(),
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header2_size : parser.uint8(),
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reserved2 : parser.buffer(2),
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advertised_size : parser.uint32LE(),
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reserved3 : parser.buffer(12),
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payload : null,
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};
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if (this._frame.signature !== 'PaVE') {
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this.emit('error', new Error('Invalid signature: ' + JSON.stringify(this._frame.signature)));
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// TODO: skip forward until next frame
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return;
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}
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// stupid kludge for https://projects.ardrone.org/issues/show/159
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parser.buffer(this._frame.header_size - PaVEParser.HEADER_SIZE_SHORT);
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this._state = 'payload';
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break;
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case 'payload':
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if (parser.bytesAhead() < this._frame.payload_size) {
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return;
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}
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this._frame.payload = parser.buffer(this._frame.payload_size);
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this.emit('data', this._frame);
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this._frame = undefined;
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this._state = 'header';
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break;
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}
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}
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return true;
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};
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PaVEParser.prototype.end = function() {
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// nothing to do, just here so pipe() does not complain
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};
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