Latest building news

building

Building a Dictaphone Using Media Recorder and getUserMedia

By feedproxy.google.com
Published On :: Tue, 17 Dec 2019 12:00:00 +0000

Chris Mills brushes up his shorthand and shows how the MediaStream Recording API in modern browsers can be used to capture audio directly from the user’s device. Inching ever closer to the capabilities of native software, it truly is an exciting time to be a web developer.

The MediaStream Recording API makes it easy to record audio and/or video streams. When used with MediaDevices.getUserMedia(), it provides an easy way to record media from the user’s input devices and instantly use the result in web apps. This article shows how to use these technologies to create a fun dictaphone app.

A sample application: Web Dictaphone

To demonstrate basic usage of the MediaRecorder API, we have built a web-based dictaphone. It allows you to record snippets of audio and then play them back. It even gives you a visualisation of your device’s sound input, using the Web Audio API. We’ll just concentrate on the recording and playback functionality in this article, for brevity’s sake.

You can see this demo running live, or grab the source code on GitHub. This has pretty good support on modern desktop browsers, but pretty patchy support on mobile browsers currently.

Basic app setup

To grab the media stream we want to capture, we use getUserMedia(). We then use the MediaRecorder API to record the stream, and output each recorded snippet into the source of a generated <audio> element so it can be played back.

We’ll first declare some variables for the record and stop buttons, and the <article> that will contain the generated audio players:

const record = document.querySelector('.record');
const stop = document.querySelector('.stop');
const soundClips = document.querySelector('.sound-clips');

Next, we set up the basic getUserMedia structure:

if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
   console.log('getUserMedia supported.');
   navigator.mediaDevices.getUserMedia (
      // constraints - only audio needed for this app
      {
         audio: true
      })

      // Success callback
      .then(function(stream) {

      })

      // Error callback
      .catch(function(err) {
         console.log('The following `getUserMedia` error occured: ' + err);
      }
   );
} else {
   console.log('getUserMedia not supported on your browser!');
}

The whole thing is wrapped in a test that checks whether getUserMedia is supported before running anything else. Next, we call getUserMedia() and inside it define:

The constraints: Only audio is to be captured for our dictaphone.
The success callback: This code is run once the getUserMedia call has been completed successfully.
The error/failure callback: The code is run if the getUserMedia call fails for whatever reason.

Note: All of the code below is found inside the getUserMedia success callback in the finished version.

Capturing the media stream

Once getUserMedia has created a media stream successfully, you create a new Media Recorder instance with the MediaRecorder() constructor and pass it the stream directly. This is your entry point into using the MediaRecorder API — the stream is now ready to be captured into a <Blob>, in the default encoding format of your browser.

const mediaRecorder = new MediaRecorder(stream);

There are a series of methods available in the MediaRecorder interface that allow you to control recording of the media stream; in Web Dictaphone we just make use of two, and listen to some events. First of all, MediaRecorder.start() is used to start recording the stream once the record button is pressed:

record.onclick = function() {
  mediaRecorder.start();
  console.log(mediaRecorder.state);
  console.log("recorder started");
  record.style.background = "red";
  record.style.color = "black";
}

When the MediaRecorder is recording, the MediaRecorder.state property will return a value of “recording”.

As recording progresses, we need to collect the audio data. We register an event handler to do this using mediaRecorder.ondataavailable:

let chunks = [];

mediaRecorder.ondataavailable = function(e) {
  chunks.push(e.data);
}

Last, we use the MediaRecorder.stop() method to stop the recording when the stop button is pressed, and finalize the Blob ready for use somewhere else in our application.

stop.onclick = function() {
  mediaRecorder.stop();
  console.log(mediaRecorder.state);
  console.log("recorder stopped");
  record.style.background = "";
  record.style.color = "";
}

Note that the recording may also stop naturally if the media stream ends (e.g. if you were grabbing a song track and the track ended, or the user stopped sharing their microphone).

Grabbing and using the blob

When recording has stopped, the state property returns a value of “inactive”, and a stop event is fired. We register an event handler for this using mediaRecorder.onstop, and construct our blob there from all the chunks we have received:

mediaRecorder.onstop = function(e) {
  console.log("recorder stopped");

  const clipName = prompt('Enter a name for your sound clip');

  const clipContainer = document.createElement('article');
  const clipLabel = document.createElement('p');
  const audio = document.createElement('audio');
  const deleteButton = document.createElement('button');

  clipContainer.classList.add('clip');
  audio.setAttribute('controls', '');
  deleteButton.innerHTML = "Delete";
  clipLabel.innerHTML = clipName;

  clipContainer.appendChild(audio);
  clipContainer.appendChild(clipLabel);
  clipContainer.appendChild(deleteButton);
  soundClips.appendChild(clipContainer);

  const blob = new Blob(chunks, { 'type' : 'audio/ogg; codecs=opus' });
  chunks = [];
  const audioURL = window.URL.createObjectURL(blob);
  audio.src = audioURL;

  deleteButton.onclick = function(e) {
    let evtTgt = e.target;
    evtTgt.parentNode.parentNode.removeChild(evtTgt.parentNode);
  }
}

Let’s go through the above code and look at what’s happening.

First, we display a prompt asking the user to name their clip.

Next, we create an HTML structure like the following, inserting it into our clip container, which is an <article> element.

<article class="clip">
  <audio controls></audio>
  <p>_your clip name_</p>
  <button>Delete</button>
</article>

After that, we create a combined Blob out of the recorded audio chunks, and create an object URL pointing to it, using window.URL.createObjectURL(blob). We then set the value of the <audio> element’s src attribute to the object URL, so that when the play button is pressed on the audio player, it will play the Blob.

Finally, we set an onclick handler on the delete button to be a function that deletes the whole clip HTML structure.

So that’s basically it — we have a rough and ready dictaphone. Have fun recording those Christmas jingles! As a reminder, you can find the source code, and see it running live, on the MDN GitHub.

This article is based on Using the MediaStream Recording API by Mozilla Contributors, and is licensed under CC-BY-SA 2.5.

About the author

Chris Mills manages the MDN web docs writers’ team at Mozilla, which involves spreadsheets, meetings, writing docs and demos about open web technologies, and occasional tech talks at conferences and universities. He used to work for Opera and W3C, and enjoys playing heavy metal drums and drinking good beer.

Mumbai's collapsed building was tagged as dangerous to live in

By archive.indianexpress.com
Published On :: Fri, 27 Sep 2013 10:21:28 GMT

The building constructed in 1980, was tagged in the C-2 category of dangerous buildings.

Building a Dictaphone Using Media Recorder and getUserMedia

A sample application: Web Dictaphone

Basic app setup

Capturing the media stream

Grabbing and using the blob

About the author

Mumbai's collapsed building was tagged as dangerous to live in

Mumbai building collapse: Death toll climbs to 61, rescue operation to be called off soon

Crushed families: Story of the survivors of the Mumbai building collapse

19 buildings operating as commercial outlets sealed in Kashmir

Infant, 2 workers killed in Bangalore building collapse

The Paris Framework for Climate Change capacity building / Mizan R. Khan, J. Timmons Roberts, Saleemul Huq and Victoria Hoffmeister

Building adaptive capacity to climate change : contributions from Australia's Marine Adaptation Network 2009-2013 / [Neil Holbrook]

Current and future impacts of climate change on housing, buildings and infrastructure / The Senate, Environment and Communications References Committee

Environmental capacity building in APEC : policies, research & programs in cleaner production : case studies in the food industry sector / edited by Robert J. Pagan & Leslie J. Williams

Seven West Bengal men dead in Mumbai building collapse

Kolkata: Security at Writers’ Building beefed up after hoax bomb email

058 JSJ Building Accessible Websites with Brian Hogan

JSJ 247 Building a Development Environment with Cory House

JSJ 268 Building Microsoft Office Extensions with JavaScript with Tristan Davis and Sean Laberee

JSJ 268 Building Microsoft Office Extensions with Javascript with Tristan Davis and Sean Laberee

Picks

JSJ 322: Building SharePoint Extensions with JavaScript with Vesa Juvonen LIVE at Microsoft Build

JSJ 323: "Building a JavaScript platform that gives you the power to build your own CDN" with Kurt Mackey

JSJ 381: Building a Personal Brand with John Sonmez

Sponsors

Panel

Episode Summary

Links

Picks

You, the people [electronic resource] : the United Nations, transitional administration, and state-building / Simon Chesterman

Your first thirty days [electronic resource] : building a professional image in a new job / Elwood N. Chapman and Robert B. Maddux

Youth and nation-building in Cameroon [electronic resource] : a study of National Youth Day messages and leadership discourse (1949-2009) / by Churchill Ewumbue-Monono

Youth peacebuilding [electronic resource] : music, gender, and change / Lesley J. Pruitt

Zenana [electronic resource] : everyday peace in a Karachi apartment building / Laura A. Ring

Process of building a civilisation

Anthranils: versatile building blocks in the construction of C–N bonds and N-heterocycles

Nanoparticles : building blocks for nanotechnology / edited by Vincent Rotello

Nanotechnology for biology and medicine : at the building block level / Gabriel A. Silva, Vladimir Parpura, editors

Increasing the durability of paint and varnish coatings in building products and construction / Loganina Valentina Ivanovna

The talent equation [electronic resource] : big data lessons for navigating the skills gap and building a competitive workforce / Matt Ferguson, Lorin Hitt, Prasanna Tambe, with Ryan Hunt and Jennifer Sullivan Grasz

Time-cost optimization of building projects [electronic resource] / by Uzair Waheed, B.E., PMP

CSS Animation Timelines: Building a Rube Goldberg Machine

Lessons from the Clean Air Act: building durability and adaptability into US climate and energy policy / edited by Ann Carlson, Dallas Burtraw

Building and System Integrator: Belgian Nuclear Research Centre (SCK-CEN)

Multi-Skilled Building Services Engineer: QinetiQ

Building a firm foundation in vacuum technology

Building climate-resilient cities

Turning wood scraps into strong, structured building material

Amy Prieto is building safer, more powerful batteries

Frances Arnold on founding a company: &#8216;Building the right teams is critical'

Video: Chemistry turns backyard clay into a 3-D printable building material

Jen Heemstra on building your resilience

Video: Chemistry turns backyard clay into a 3-D printable building material

Merdad Parsey on building a case for remdesivir amid the coronavirus pandemic

Colorful paints could keep buildings cool

Tracking copper, chlorine, and occupancy in a new, multi-story, institutional green building

Bacterial community structure correlates with Legionella pneumophila colonization of New York City high rise building premises plumbing systems

Field testing of an onsite sanitation system on apartment building blackwater using biological treatment and electrochemical disinfection

ED attaches part of AJL Mumbai building worth Rs 16.38 cr; charges Moti Lal Vora

CERN and the Higgs boson: the global quest for the building blocks of reality / James Gillies

Rethinking third places: informal public spaces and community building / edited by Joanne Dolley, Caryl Bosman

The Finish Line: Building Walls in the Land Down Under

Building Product Transparency— Be Careful What You Ask For

An Energy Label for Buildings

New Gadget Analyzes Everything Including Building Industry

Green Building Mistakes

Is a LEED Building Healthy?

Embodied Energy of Building Materials

VIDEO: The Great Heights of the Building Arts

How can Scotland re-establish its building stone industry? - British Geological Survey

Building/sustaining safety cultures: EHS pros’ top priority for ’15, says ISHN survey

AI and the Building Blocks of Intelligent Content

Missing Berlin’s gorgeous buildings again. ???? (at Berlin,...

Building Digital Tools Without the Hype

Airtron Canada Awarded Major HVAC and Building Automation Contract

Canada Tops International List of Top 10 Countries for LEED Green Building

Subscribe To Our Newsletter

Frances Arnold on founding a company: ‘Building the right teams is critical'