ts-ebml

ebml encoder and decoder written in TypeScript.

Fork of node-ebml

It is a fork of https://github.com/themasch/node-ebml

install

npm install ts-ebml --save

usage

show EBML structure on console

$ ts-ebml foo.webm
0	m	0	EBML
5	u	1	EBMLVersion 1
9	u	1	EBMLReadVersion 1
13	u	1	EBMLMaxIDLength 4
17	u	1	EBMLMaxSizeLength 8
21	s	1	DocType webm
28	u	1	DocTypeVersion 2
32	u	1	DocTypeReadVersion 2
36	m	0	Segment
48	m	1	Info
53	u	2	TimecodeScale 1000000
...

try to convert a MediaRecorder WebM to seekable WebM

$ ts-ebml -s input.webm | cat > seekable.webm

node

import * as ebml from 'ts-ebml';
const fs = require('fs');

const decoder = new ebml.Decoder();

fs.createReadStream('media/test.webm').on('data', (buf)=>{
  const ebmlElms = decoder.decode(buf);
  console.log(ebmlElms);
});

browser

<script src="./dist/ebml.min.js"></script>
<script>
const decoder = new ebml.Decoder();

fetch('media/test.webm')
  .then((res)=> res.arrayBuffer() )
  .then((buf)=>{
    const ebmlElms = decoder.decode(buf);
    console.log(ebmlElms);
  });  
</script>

bundle

import * as ebml from 'ts-ebml';

const decoder = new ebml.Decoder();

fetch('media/test.webm')
  .then((res)=> res.arrayBuffer() )
  .then((buf)=>{
    const ebmlElms = decoder.decode(buf);
    console.log(ebmlElms);
  });

features

• get WebP frame from MediaRecorder WebM VP8 Stream
• create seekable webm from media-recoder
• create playable webm to media-stream-api from media-recorder

see src/test.ts and src/example_seekable.ts

stable API

class Decoder {
  constructor();
  decode(chunk: ArrayBuffer): EBMLElementDetail[];
}

class Encoder {
  constructor();
  encode(elms: EBMLElementBuffer[]): ArrayBuffer;
}

type EBMLElementBuffer = MasterElement | ChildElementBuffer;
type EBMLElementDetail = (MasterElement | ChildElementValue) & ElementDetail;

type MasterElement = {
  name: string;
  type: "m";
  isEnd: boolean;
  unknownSize?: boolean;
};
type ChildElementBuffer = {
  name: string;
  type: "u" | "i" | "f" | "s" | "8" | "b" | "d";
  data: Buffer;
};
type ChildElementValue = ChildElementBuffer & {
  value: number|string|Buffer|Date;
};
type ElementDetail = {
  tagStart: number;
  tagEnd: number;
  sizeStart: number;
  sizeEnd: number;
  dataStart: number;
  dataEnd: number;
};
namespace tools {
  export function readVint(buffer: Buffer, start: number): null | ({length: number; value: number; });
  export function writeVint(val: number): Buffer;
  export function readBlock(buf: ArrayBuffer): EBML.SimpleBlock;
}

develop

npm install
npm run build   # build js code
npm run lint    # tslint
npm run doc     # typedoc
npm run lint   # type check (watch)
npm test        # build and run tests

debugging tools

• https://www.matroska.org/downloads/mkvalidator.html
• https://www.matroska.org/downloads/mkclean.html
• https://mkvtoolnix.download/doc/mkvinfo.html
• https://github.com/ietf-wg-cellar/matroska-test-files
• MOZ_LOG_FILE="log.txt" MOZ_LOG="MediaDemuxer:5" /Applications/FirefoxNightly.app/Contents/MacOS/firefox-bin
• MOZ_LOG_FILE="log.txt" MOZ_LOG="MediaDemuxer:5" /Applications/Firefox.app/Contents/MacOS/firefox-bin
• chrome://media-internals/
• chrome://webrtc-internals/
• ./out/gn/Chromium.app/Contents/MacOS/Chromium -vmodule="video=0,ffmpeg=1,media=1" https://webrtc.github.io/samples/src/content/getusermedia/record/
• ffmpeg -i not_seekable.webm -c copy seekable.webm
• mkclean --doctype 4 --keep-cues --optimize not_seekable.webm seekable.webm
• webm_info -a foo.webm - https://chromium.googlesource.com/webm/libwebm

license

MIT

related info

• https://www.matroska.org/technical/specs/index.html
• https://www.matroska.org/technical/specs/notes.html
• https://www.matroska.org/technical/order/index.html

related issues

media recorder seekable webm

chrome

• MediaRecorder output should have Cues element - https://bugs.chromium.org/p/chromium/issues/detail?id=561606
• Videos created with MediaRecorder API are not seekable / scrubbable - https://bugs.chromium.org/p/chromium/issues/detail?id=569840
• No duration or seeking cue for opus audio produced with mediarecoder - https://bugs.chromium.org/p/chromium/issues/detail?id=599134
• MediaRecorder: consider producing seekable WebM files - https://bugs.chromium.org/p/chromium/issues/detail?id=642012

firefox

• Seeking in WebM files with no Cues element is not supported - https://bugzilla.mozilla.org/show_bug.cgi?id=657791
• Recorder video clips result can't replay /seekable on firefox - https://bugzilla.mozilla.org/show_bug.cgi?id=969290

others

• Optimizing WebM Video for Faster Streaming and Seeking - https://rigor.com/blog/2016/02/optimizing-webm-video-for-faster-streaming-and-seeking
• Creation of Seekable Files - https://github.com/w3c/mediacapture-record/issues/119

media recorder media source gap

chrome

• MediaSource api not able to play webm video recorded from MediaRecorder - https://bugs.chromium.org/p/chromium/issues/detail?id=606000
• Video playback freezes using MediaSource API (MSE) - https://bugs.chromium.org/p/chromium/issues/detail?id=678269
• MediaSource API: Appending chunks to a SourceBuffer creates gaps and playback stops - https://bugs.chromium.org/p/chromium/issues/detail?id=688490
• Playback of video segments freezes with errors in media-internals - https://bugs.chromium.org/p/chromium/issues/detail?id=711829

others

chrome

• Regression: Playback of mediaStream recording shows blank video - https://bugs.chromium.org/p/chromium/issues/detail?id=657532

firefox

• Webm video recorded with MediaRecorder cannot be played more than once - https://bugzilla.mozilla.org/show_bug.cgi?id=1272371

related works

• https://github.com/antimatter15/js-ebml
• https://bitbucket.org/desmaj/libvpx.js/src/1ea3218282b6eb129061341831d23409dd539054/webm.js
• https://github.com/themasch/node-ebml
• https://github.com/oeuillot/node-matroska
• https://github.com/eadle/webm-byte-stream
• https://github.com/mafintosh/webm-cluster-stream
• https://github.com/Matroska-Org/libebml/
• https://github.com/Matroska-Org/foundation-source
• https://github.com/webmproject/libwebm
• https://chromium.googlesource.com/webm/libvpx/+/master/third_party/libwebm
• https://github.com/mozilla/gecko-dev/tree/master/dom/media/webm
• https://github.com/yellowdoge/libwebm