Ts-ebml NPM | npm.io

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