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A day after the state home department issued an order allowing certain categories of shops to reopen, some electronics, electrical and vehicle spare parts shops reopened in the city on Thursday.

Ezzamel, Mahmoud

Hayden Library - QP461.E34 2015

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Hayden Library - QP382.F7 H85 2018

Mullah Akhtar Mansour was killed in a drone strike in 2016

In our first segment from the annual meeting of AAAS (Science’s publisher) in Washington, D.C., host Sarah Crespi talks with Cathy Binger of University of New Mexico in Albuquerque about her session on the role of modern technology, such as iPads and apps, in helping people with communication disorders. It turns out that there’s no killer app, but some devices do help normalize assistive technology for kids. Also this week, freelance journalist Sarah Scoles joins Sarah Crespi to talk about bringing together satellite imaging, machine learning, and nonprofits to put a stop to modern-day slavery. In our monthly books segment, books editor Valerie Thompson talks with Judy Grisel about her book Never Enough: The Neuroscience and Experience of Addiction, including discussions of Gisel’s personal experience with addiction and how it has informed her research as a neuroscientist. This week’s episode was edited by Podigy. Download the transcript (PDF) Listen to previous podcasts. About the Science Podcast [Image: ILO in Asia and the Pacific/Flickr; Music: Jeffrey Cook]

Abingdon, Oxon : Routledge, 2019.

Tucson : University of Arizona Press, 2020.

Dewey Library - HE395.N74 L37 2018

Dewey Library - HE8699.M4 R63 2019

Dabashi, Hamid, 1951- author

The Supreme Court stayed the order after the Centre said it was ‘unworkable’ and passed without consultation.

The court noted that there was a “blatant violation” of its guidelines regulating the sale of liquor.

While courts have an important role in ensuring that the rights of citizens are protected, it is essential that they avoid adjudicating on policy matters.

On Friday, the Madras High Court noted that there was a ‘blatant violation’ of its guidelines regulating liquor sales and ordered only online sale.

The authors developed a mathematical model based on a cost-of-illness approach to estimate the impacts of exposure to untreated PMADs on mothers and children.

Tamil Nadu is ordering 10 lakh more RT-PCR (reverse transcription-polymerase chain reaction) testing kits to ramp up testing across the State.Accordin

The Madras High Court on Friday directed the State government to close all 3,850 liquor shops run by the Tamil Nadu State Marketing Corporation (Tasma

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.

More articles by Chris

Hayden Library - HV6439.M58 D87 2018

Dewey Library - JC355.B67 2018

Hearing after SC decides Adarsh Society's plea seeking transfer of the matter to National Green Tribunal.

Enquiry committee set up following allegations of irregularities by Cong MP Naveen Jindal's company.

Earlier SC had asked the Centre not to issue Aadhar cards to illegal immigrants.

This is the second such incident in the last 5 days after jawans beat up officers in Meerut in UP.

Ceasefire violations has increased as Pak troops violated border truce nearly 130 times along LoC.

This comes nearly a week after Pakistan's earlier ceasefire violation that killed India's Lance Naik.

Pakistan Rangers have targeted nearly 50 BSF posts along the International border.

The apex court has pulled up ex-Army chief V K Singh for his comments on its verdict.

Minutes after he managed to flee, Usmani got his beard trimmed by a roadside barber.

They have been housed in community centres at places out of the shelling range.

This is intended to allow farmers to harvest crops in the Zero line on Jammu frontier.

The petitioner said Tamil Nadu Judicial Service rules 2007 allow the blind/deaf advocates to apply.

Security tightened along border, curfew in force from 7 pm to 6 am within 2 km inside Assam.

BSF is at present deployed on the frontiers with Pakistan and Bangladesh.