Kalinga Komati’s State president Boina Govindarajulu met CM Chandrababu Naidu and submitted a detailed petition for his perusal

How regulation can nudge private banks to promote financial inclusion

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

The RBI has explained its food inflation concerns for those who discount them in the context of monetary policy — while flagging financial stability issues

The Company achieved a 22 per cent % year-on-year increase in net profit in Q2 FY25, driven by business growth, stable asset quality, and a continuous focus on enhancing productivity

Describing the decision as historic, AMUTA looks forward to the speedy resolution of the minority character case as directed by the norms of the Constitutional Bench

BJP to strongly defend Aligarh Muslim University’s minority status in Supreme Court, overruling 1967 judgement

Vice-Chancellor Naima Khatoon said the judgment paved way for the granting of minority status to the varsity. Students celebrated the day by distributing sweets at the varsity gate.

The Modi government should take this judgement in its stride, says Asad

Ramanuja’s interpretations of the Sanskrit verses proved that he had the potential of being a good commentator.

Post the Paris Olympics, the association has planned to completely restructure its training and competition modules, possibly allowing more freedom and opportunities to athletes in both; this includes doing away with centralised national camps, grading the training centres and academies and increasing regional events for easy access to competitions

Soon after the school reopens, the pair turns brown in the slush and mud

The interest rates on small savings schemes such as Public Provident Fund (PPF) and National Savings Certificate (NSC) are reset each quarter

As part of a seven-judge Constitution bench, Justice Sharma, along with a majority, overruled a 1967 verdict that denied Aligarh Muslim University’s minority institution status.

Yamini Narayanan argues that the cow and the Ganga have both been harmed, in the name of being sacred

Leipzig : T. O. Weigel, 1870.

Chennai-based Annie Titus Mammen, who does embroidery for Chanel, Balenciaga and Louis Vuitton, has launched Tambour’s first Independent product line of embellished pashmina stoles in Delhi

A PIL petition complains about the dilapidated condition of the building and seeks a direction to authorities to construct a new one in its place.

Aims to strengthen commodities segment, predicts market cap to double in 10 years

Centrum Broking

'While criticising India's high tariffs, Mr Trump stated he would impose reciprocal taxes on Indian products if re-elected.'

The BJP MLC said that while seeking votes for him, she felt like she was receiving a "send-off party" and was being freed of a responsibility.

CP Group said it would fund the deal with cash flow from group companies and loans.

The post Tesco Lotus set to return to Thai conglomerate CP Group’s stable in $10.6b deal appeared first on DealStreetAsia.

1. Prince Harry urges Invictus Games family to rally  PerthNow
2. Prince Harry marks Invictus Games in new video message: Watch  NEWS.com.au
3. 'Life has changed dramatically': Harry shares unexpected video from new LA home  9Honey
4. ‘Life has changed dramatically’: Harry’s surprise video from Hollywood home  7NEWS.com.au
5. Prince Harry says 'life has changed dramatically for us all' in new message from LA  Daily Star
6. View Full coverage on Google News

The Duke of Sussex sent a special video message to mark what would have been the opening ceremony of the 2020 Invictus Games.

This report analyzes prenatal behaviors and birth outcomes of Black immigrant mothers, and finds that Black immigrant mothers are less likely to give birth to preterm or low-birth-weight infants than U.S.-born Black women, but more likely to experience these birth outcomes than other immigrant and U.S.-born women.

Testimony of Margie McHugh, Co-Director of MPI's National Center on Immigrant Integration Policy, before the House Judiciary Subcommittee on Immigration and Border Security, U.S. House of Representatives.

Status2k remote add administrator exploit.

SUSE/Portus version 2.2 suffers from a persistent cross site scripting vulnerability.

The headline figure from the authoritative REN21 Renewables Global Status Report 2015 (GSR) states renewables accounted for more than 59 percent of all new electricity generating capacity installed worldwide during 2014.

Detectives posing as potential buyers nab suspects.

The Duke of Sussex has reflected on how "dramatically" life has changed, as he marked what would have been the opening ceremony of the Invictus Games.

1. Coronavirus cases jump to near 63,000 in India, 2,109 deaths. State-wise status  Livemint
2. Total Number Of COVID-19 cases In India Rise to 62939, Death Toll At 2109 | CNN News18  CNN-News18
3. Coronavirus India News LIVE: Known COVID-19 cases near 63000; Bihar's tally rises to 629  Moneycontrol
4. Mint Covid Tracker: Fresh infections, deaths rising faster in India than most countries  Livemint
5. India’s Covid-19 cases near 63,000-mark, death toll at 2,109  Top Live News
6. View Full coverage on Google News

Lotus technical chief Mike Gascoyne said his team's performance in Canada was a 'massive step forward'

Lotus' Tony Fernandes could not contain his delight after witnessing his team's Formula One re-birth 16 years after Lotus last competed in the sport

Heikki Kovalainen says the Malaysian Grand Prix was a positive race for the team as both cars made it to the finish line, albeit in 17th and 18th positions