10.6 DTMF Example

Examples assume that sender is an RTCRtpSender.

Sending the DTMF signal “1234” with 500 ms duration per tone:

Example 13

  1. if (sender.dtmf.canInsertDTMF) {
  2.   const duration = 500;
  3.   sender.dtmf.insertDTMF('1234', duration);
  4. } else {
  5.   console.log('DTMF function not available');
  6. }

Send the DTMF signal “123” and abort after sending “2”.

Example 14

  1. async function sendDTMF() {
  2.   if (sender.dtmf.canInsertDTMF) {
  3.     sender.dtmf.insertDTMF('123');
  4.     await new Promise(r => sender.dtmf.ontonechange = e => e.tone == '2' && r());
  5.     // empty the buffer to not play any tone after "2"
  6.     sender.dtmf.insertDTMF('');
  7.   } else {
  8.     console.log('DTMF function not available');
  9.   }
  10. }

Send the DTMF signal “1234”, and light up the active key using lightKey(key) while the tone is playing (assuming that lightKey("") will darken all the keys):

Example 15

  1. const wait = ms => new Promise(resolve => setTimeout(resolve, ms));
  3. if (sender.dtmf.canInsertDTMF) {
  4.   const duration = 500; // ms
  5.   sender.dtmf.insertDTMF(sender.dtmf.toneBuffer + '1234', duration);
  6.   sender.dtmf.ontonechange = async ({tone}) => {
  7.     if (!tone) return;
  8.     lightKey(tone); // light up the key when playout starts
  9.     await wait(duration);
  10.     lightKey(''); // turn off the light after tone duration
  11.   };
  12. } else {
  13.   console.log('DTMF function not available');
  14. }

It is always safe to append to the tone buffer. This example appends before any tone playout has started as well as during playout.

Example 16

  1. if (sender.dtmf.canInsertDTMF) {
  2.   sender.dtmf.insertDTMF('123');
  3.   // append more tones to the tone buffer before playout has begun
  4.   sender.dtmf.insertDTMF(sender.dtmf.toneBuffer + '456');
  6.   sender.dtmf.ontonechange = ({tone}) => {
  7.     // append more tones when playout has begun
  8.     if (tone != '1') return;
  9.     sender.dtmf.insertDTMF(sender.dtmf.toneBuffer + '789');
  10.   };
  11. } else {
  12.   console.log('DTMF function not available');
  13. }

Send a 1-second “1” tone followed by a 2-second “2” tone:

Example 17

  1. if (sender.dtmf.canInsertDTMF) {
  2.   sender.dtmf.ontonechange = ({tone}) => {
  3.     if (tone == '1') {
  4.       sender.dtmf.insertDTMF(sender.dtmf.toneBuffer + '2', 2000);
  5.     }
  6.   };
  7.   sender.dtmf.insertDTMF(sender.dtmf.toneBuffer + '1', 1000);
  8. } else {
  9.   console.log('DTMF function not available');
  10. }