2a09d1a4
 liuqimichale
添加宜春 天水 宣化
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'use strict';
var FlvTag = require('./flv-tag.js');
// For information on the FLV format, see
// http://download.macromedia.com/f4v/video_file_format_spec_v10_1.pdf.
// Technically, this function returns the header and a metadata FLV tag
// if duration is greater than zero
// duration in seconds
// @return {object} the bytes of the FLV header as a Uint8Array
var getFlvHeader = function(duration, audio, video) { // :ByteArray {
var
headBytes = new Uint8Array(3 + 1 + 1 + 4),
head = new DataView(headBytes.buffer),
metadata,
result,
metadataLength;
// default arguments
duration = duration || 0;
audio = audio === undefined ? true : audio;
video = video === undefined ? true : video;
// signature
head.setUint8(0, 0x46); // 'F'
head.setUint8(1, 0x4c); // 'L'
head.setUint8(2, 0x56); // 'V'
// version
head.setUint8(3, 0x01);
// flags
head.setUint8(4, (audio ? 0x04 : 0x00) | (video ? 0x01 : 0x00));
// data offset, should be 9 for FLV v1
head.setUint32(5, headBytes.byteLength);
// init the first FLV tag
if (duration <= 0) {
// no duration available so just write the first field of the first
// FLV tag
result = new Uint8Array(headBytes.byteLength + 4);
result.set(headBytes);
result.set([0, 0, 0, 0], headBytes.byteLength);
return result;
}
// write out the duration metadata tag
metadata = new FlvTag(FlvTag.METADATA_TAG);
metadata.pts = metadata.dts = 0;
metadata.writeMetaDataDouble('duration', duration);
metadataLength = metadata.finalize().length;
result = new Uint8Array(headBytes.byteLength + metadataLength);
result.set(headBytes);
result.set(head.byteLength, metadataLength);
return result;
};
module.exports = getFlvHeader;
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