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MP4Muxer.js
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MP4Muxer.js
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function add_atom(atom, sub_atom){
'use strict';
atom.size += sub_atom.size;
atom.box.push.apply(atom.box, sub_atom.box);
}
function ftyp(){
'use strict';
var buffer = new ArrayBuffer(32),
view = new DataView(buffer);
view.setUint32(0, 32); // box size
view.setUint32(4, 0x66747970); // 'ftyp'
view.setUint32(8, 0x69736f6d); //major brand 'isom'
view.setUint32(12, 512); //minor version
view.setUint32(16, 0x69736f6d); //isom
view.setUint32(20, 0x69736f32); //iso2
view.setUint32(24, 0x61766331); //avc1
view.setUint32(28, 0x6d703431); //mp41
return {size: 32, box: [buffer]};
}
function mdat(tracks){
'use strict';
var datas = tracks.map(function(track){ return track.data.buffer; }),
length = datas.reduce(function(p,n){ return p + n.byteLength; },8),
buffer = new ArrayBuffer(8),
view = new DataView(buffer);
view.setUint32(0, length);
view.setUint32(4, 0x6d646174); // mdat
return {size: length, box: [buffer].concat(datas)};
}
function hdlr(trkdata){
'use strict';
var buffer = new ArrayBuffer(45),
view = new DataView(buffer);
view.setUint32(0, 45);
view.setUint32(4, 0x68646c72); // hdlr
if(trkdata.type==='v'){
view.setUint32(16, 0x76696465); // vide
view.setUint32(32, 0x56696465); // 'Vide'
view.setUint32(36, 0x6f48616e); //'oHan'
}else{
view.setUint32(16, 0x736f756e); // soun
view.setUint32(32, 0x536f756e); // 'Soun'
view.setUint32(36, 0x6448616e); //'dHan'
}
view.setUint32(40, 0x646c6572); // 'dler'
return {size: 45, box: [buffer]};
}
function vmhd(){
'use strict';
var buffer = new ArrayBuffer(20),
view = new DataView(buffer);
view.setUint32(0, 20);
view.setUint32(4, 0x766d6864); // vmhd
view.setUint32(8, 1); // version & flags
// graphicsmode(16) & opcolor(16)[3]
return {size: 20, box: [buffer]};
}
function smhd(){
'use strict';
var buffer = new ArrayBuffer(16),
view = new DataView(buffer);
view.setUint32(0, 16);
view.setUint32(4, 0x736d6864); // smhd
// version & flags, balance & reserved
return {size: 16, box: [buffer]};
}
function dinf(){
'use strict';
var buffer = new ArrayBuffer(37),
view = new DataView(buffer);
view.setUint32(0, 37);
view.setUint32(4, 0x64696e66); // dinf
// Data Reference sub-box
view.setUint32(8, 29);
view.setUint32(12, 0x64726566); // dref
// flags
view.setUint32(20, 1); // entry count
//DataEntryUrl sub-box
view.setUint32(24, 13);
view.setUint32(28, 0x75726c20); // 'url '
view.setUint32(32, 1); // self-contained flag
//no url string in self-contained version
return {size: 37, box: [buffer]};
}
function stts(dts_diffs){
'use strict';
var i, j,
c = dts_diffs.length,
l = c * 8 + 16,
buffer = new ArrayBuffer(l),
view = new DataView(buffer);
view.setUint32(0, l); // size
view.setUint32(4, 0x73747473); // stts
//version & flags are zero
view.setUint32(12, c); // entry count
for(i=0, j=16; i < c; i++, j+=8){
view.setUint32(j, dts_diffs[i].sample_count);
view.setUint32(j+4, dts_diffs[i].sample_delta);
}
return {size: l, box: [buffer]};
}
function ctts(pd_diffs){
'use strict';
var i, j,
c = pd_diffs.length,
l = c * 8 + 16,
buffer = new ArrayBuffer(l),
view = new DataView(buffer);
view.setUint32(0, l); // size
view.setUint32(4, 0x63747473); // ctts
//version & flags are zero
view.setUint32(12, c); // entry count
for(i=0, j=16; i < c; i++, j+=8){
view.setUint32(j, pd_diffs[i].sample_count);
view.setUint32(j+4, pd_diffs[i].sample_offset);
}
return {size: l, box: [buffer]};
}
function stss(indices){
'use strict';
var i, j, c = indices.length,
l = c * 4 + 16,
buffer = new ArrayBuffer(l),
view = new DataView(buffer);
view.setUint32(0, l); // size
view.setUint32(4, 0x73747373); // stss
//version & flags are zero
view.setUint32(12, c); // entry count
for(i=0, j=16; i < c; i++, j+=4){
view.setUint32(j, indices[i]);
}
return {size: l, box: [buffer]};
}
function stsz(sizes){
'use strict';
var i, j, c = sizes.length,
l = c * 4 + 20,
buffer = new ArrayBuffer(l),
view = new DataView(buffer);
view.setUint32(0, l); // size
view.setUint32(4, 0x7374737a); // stsz
//version & flags are zero
view.setUint32(16, c); // sample count
for(i=0, j=20; i < c; i++, j+=4){
view.setUint32(j, sizes[i]);
}
return {size: l, box: [buffer]};
}
function stsc(samples){
'use strict';
var buffer = new ArrayBuffer(28),
view = new DataView(buffer);
view.setUint32(0, 28);
view.setUint32(4, 0x73747363); // stsc
view.setUint32(12, 1);
view.setUint32(16, 1);
view.setUint32(20, samples);
view.setUint32(24, 1);
return {size: 28, box: [buffer]};
}
function stco(offset){
'use strict';
var buffer = new ArrayBuffer(20),
view = new DataView(buffer);
view.setUint32(0, 20);
view.setUint32(4, 0x7374636f); // stco
view.setUint32(12, 1);
view.setUint32(16, offset);
return {size: 20, box: [buffer]};
}
function avcC(trkdata){
'use strict';
var i, j,
sps = trkdata.sps,
pps = trkdata.pps,
spslen = sps.byteLength,
ppslen = pps.byteLength,
len = spslen + ppslen + 19,
spsInfo = trkdata.spsInfo,
buffer = new ArrayBuffer(len),
view = new DataView(buffer);
view.setUint32(0, len);
view.setUint32(4, 0x61766343); // avcC
view.setUint8(8, 1); // version
view.setUint8(9, spsInfo.profile_idc);
view.setUint8(10, spsInfo.profile_compatibility);
view.setUint8(11, spsInfo.level_idc);
view.setUint8(12, 0xff); // 6 bits reserved + lengthSizeMinus1
view.setUint8(13, 0xe1); // 3 bits reserved + SPS count
view.setUint16(14, spslen);
for(i = 0, j = 16; i < spslen; i++, j++){
view.setUint8(j, sps[i]);
}
view.setUint8(16+spslen, 1); // PPS count
view.setUint16(17+spslen, ppslen);
for(i = 0, j = 19+spslen; i < ppslen; i++, j++){
view.setUint8(j, pps[i]);
}
return {size: len, box: [buffer]};
}
function avc1(trkdata){
'use strict';
var buffer = new ArrayBuffer(86),
view = new DataView(buffer),
atom = {size: 86, box: [buffer]};
view.setUint32(4, 0x61766331); // avc1
// six bytes reserved
view.setUint16(14, 1); // data reference index
// VisualSampleEntry data
// 4 words / 16 bytes predefined & reserved space, all zeroes
view.setUint16(32, trkdata.width); // width
view.setUint16(34, trkdata.height); // height
view.setUint32(36, 0x00480000); // 72dpi horiz res.
view.setUint32(40, 0x00480000); // 72dpi vert res.
// 4 bytes reserved
view.setUint16(48, 1); // frame count
// 32 bytes / 8 words of empty compressor name string
view.setUint16(82, 24); // bit depth
view.setInt16(84, -1); // predefined
add_atom(atom, avcC(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function esds(trkdata){
'use strict';
var buffer = new ArrayBuffer(39),
view = new DataView(buffer),
freqIndex = trkdata.samplingFreqIndex,
objectType = trkdata.profileMinusOne + 1,
channelConf = trkdata.channelConfig;
view.setUint32(0, 39); // size
view.setUint32(4, 0x65736473); // esds
//ES_Descriptor
view.setUint8(12, 3); // ES_DescrTag
view.setUint8(13, 34); // length
view.setUint16(15, 2); // ES_ID
// priority + flags byte = 0
//DecoderConfigDescriptor
view.setUint8(17, 4); // DecoderConfigDescrTag
view.setUint8(18, 20); // length
view.setUint8(19, 0x40); // objectTypeIndication = MPEG4 Audio ISO/IEC 14496-3
view.setUint8(20, 0x15); // streamType = 5 (Audio), upStream = 0, reserved = 0
// 3 byte bufferSize = 0
view.setUint32(24, trkdata.maxBitrate);
view.setUint32(28, trkdata.avgBitrate);
// DecoderSpecificInfo
view.setUint8(32, 5); // DecSpecificInfoTag
view.setUint8(33, 2); // length
view.setUint16(34, (objectType<<11)|(freqIndex<<7)|(channelConf<<3));
// SLConfigDescriptor
view.setUint8(36, 6); //SLConfigDescrTag
view.setUint8(37, 1); // length
view.setUint8(38, 2); // MP4 = 2
return {size: 39, box: [buffer]};
}
function mp4a(trkdata){
'use strict';
var buffer = new ArrayBuffer(36),
view = new DataView(buffer),
atom = {size: 36, box: [buffer]};
view.setUint32(4, 0x6d703461); // mp4a
// 6 bytes reserved
view.setUint16(14, 1); // data reference index
// AudioSampleEntry data
// 8 bytes reserved
view.setUint16(24, 2); // channel count
view.setUint16(26, 16); // sample size
// 4 bytes reserved
view.setUint32(32, 22050<<16); // sample rate
// mp4a extends AudioSampleEntry with ESDBox
add_atom(atom, esds(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function stsd(trkdata){
'use strict';
var buffer = new ArrayBuffer(16),
view = new DataView(buffer),
atom = {size: 16, box: [buffer]};
view.setUint32(4, 0x73747364); // stsd
view.setUint32(12, 1); // entry count
add_atom(atom, (trkdata.type === 'v'?avc1:mp4a)(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function stbl(trkdata){
'use strict';
var buffer = new ArrayBuffer(8),
view = new DataView(buffer),
atom = {size: 8, box: [buffer]};
view.setUint32(4, 0x7374626c);
add_atom(atom, stsd(trkdata));
add_atom(atom, stts(trkdata.dts_diffs));
add_atom(atom, stsc(trkdata.sizes.length));
add_atom(atom, stsz(trkdata.sizes));
add_atom(atom, stco(trkdata.byte_offset));
if(trkdata.type === 'v'){
add_atom(atom, stss(trkdata.access_indices));
if(trkdata.pd_diffs.length){
add_atom(atom, ctts(trkdata.pd_diffs));
}
}
view.setUint32(0, atom.size);
return atom;
}
function minf(trkdata){
'use strict';
var buffer = new ArrayBuffer(8),
view = new DataView(buffer),
atom = {size: 8, box: [buffer]};
view.setUint32(4, 0x6d696e66);
add_atom(atom, (trkdata.type === 'v'?vmhd:smhd)());
add_atom(atom, dinf());
add_atom(atom, stbl(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function mdia(trkdata){
'use strict';
var buffer = new ArrayBuffer(40),
view = new DataView(buffer),
atom = {size: 40, box: [buffer]};
view.setUint32(4, 0x6d646961);
// mdhd sub-box
view.setUint32(8, 32);
view.setUint32(12, 0x6d646864); // mdhd
//view.setUint32(20, t); // creation time
//view.setUint32(24, t); // modification time
view.setUint32(28, trkdata.timescale);
view.setUint32(32, Math.round(trkdata.duration*trkdata.timescale));
view.setUint32(36, 0x55c40000); // 15-bit lang code 'und' & predefined = 0
add_atom(atom, hdlr(trkdata));
add_atom(atom, minf(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function trak(id, trkdata){
'use strict';
var buffer = new ArrayBuffer(100),
view = new DataView(buffer),
atom = {size: 100, box: [buffer]};
view.setUint32(4, 0x7472616b); // trak
// tkhd sub-box
view.setUint32(8, 92);
view.setUint32(12, 0x746b6864); // tkhd
view.setUint32(16, 15); // version & flags
//view.setUint32(20, t); // creation time
//view.setUint32(24, t); // modification time
view.setUint32(28, id);
view.setUint32(36, trkdata.duration*1000); //or all 1s
// reserved, layer(16) & alternate group(16)
view.setUint32(48, trkdata.type == 'v' ? 0 : 0x01000000); // volume & more reserved
// identity matrix:
view.setUint32(52, 0x01000000 );
view.setUint32(68, 0x00010000);
view.setUint32(88, 0x40000000);
view.setUint32(92, (trkdata.width&0xffff)<<16); // 16.16 width, ignoring fractional part
view.setUint32(96, (trkdata.height&0xffff)<<16); // 16.16 height, ignoring fractional part
add_atom(atom, mdia(trkdata));
view.setUint32(0, atom.size);
return atom;
}
function moov(tracks){
'use strict';
var d, buffer = new ArrayBuffer(116),
view = new DataView(buffer),
atom = {size: 116, box: [buffer]};
d = Math.max.apply(Math,
tracks.map(function(trkdata){ return trkdata.duration; })
);
view.setUint32(4, 0x6d6f6f76); // moov
// mvhd sub-box
view.setUint32(8, 108);
view.setUint32(12, 0x6d766864); // mvhd
//view.setUint32(20, t); // creation time
//view.setUint32(24, t); // modification time
view.setUint32(28, 1000); // timescale
view.setUint32(32, Math.round(d*1000)); //duration
view.setUint32(36, 0x00010000); // rate = 1.0
view.setUint32(40, 0x01000000); // volume = 1.0 + reserved(16)
// 64 bits reserved
// identity matrix:
view.setUint32(52, 0x00010000);
view.setUint32(68, 0x00010000);
view.setUint32(84, 0x40000000);
// predefined (32)[6]
view.setUint32(112, tracks.length); // next track id
tracks.forEach(function(trkdata, i){ add_atom(atom, trak(i+1, trkdata)); });
view.setUint32(0, atom.size);
return atom;
}
function MP4(tracks){
'use strict';
var offset,
atom = {size: 0, box: []};
add_atom(atom, ftyp());
offset = atom.size + 8;
tracks.forEach(function(track){
track.byte_offset = offset;
offset += track.data.byteLength;
});
add_atom(atom, mdat(tracks));
add_atom(atom, moov(tracks));
return new Blob(atom.box, {type: 'video/mp4'});
}