Original link: https://blog.est.im/2022/stdout-10
When playing with WebRTC, I found that it actually supports DTMF dial tone built-in. So I got interested and wanted to make a demo to play with
After writing for a long time, the debugging fails, and an error is reported
VM987:1 Uncaught DOMException: Failed to execute ‘insertDTMF’ on ‘RTCDTMFSender’: The ‘canInsertDTMF’ attribute is false: this sender cannot send DTMF.
After carefully studying this thing , it turns out that WebRTC does not transmit audio directly, but sends a control signal, and the receiver plays the audio, so you need to create a real duplex RTC locally and open the microphone permission to play DTMF audio.
WebRTC doesn’t send DTMF codes as audio data. Instead, they’re sent out-of-band, as RTP payloads. Note, however, that although it’s possible to send DTMF using WebRTC, there is currently no way to detect or receive incoming DTMF. WebRTC currently ignores these payloads;
This goes far. So I used AudioContext() to paste it again. A total of less than 1000 bytes.
https://lab.est.im/dtmf source code
Um. It’s pretty simple. In particular, the oscillator has a .stop(0.2) parameter to avoid the trouble of setTimeout . There are many tutorials online that are quite complicated.
Btw hang some old scripts under the lab domain name.
Btw2 changed the RSS to full text output.
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