A student's open lab: learning and sharing, free for everyone.

SIP UniverseFree University

Home / WebRTC and SIP over WebSocket / DTLS-SRTP and the required audio codecs

DTLS-SRTP and the required audio codecs

WebRTC media is SRTP. The profile is RTP/SAVPF. Opus, PCMA, and PCMU are required audio codecs.

Learn in 5 minutes

  1. Say where DTLS-SRTP keys are made
  2. Write the UDP proto token from RFC 5764
  3. List the required WebRTC audio codecs

Visual

SIP offers the description. DTLS keys the packets. · study drawing · cyphermonkeylabs.com BrowserGateway INVITE 100 200 DTLS

SVG HTML PNG

DTLS-SRTP does not put the SRTP key in the SIP message. The codec list is a separate requirement.

Worked example

Read the offer proto and the Opus line The offer uses UDP/TLS/RTP/SAVPF and names opus/48000/2. The answer keeps Opus.

  1. Press Negotiate.
  2. Read the proto token.
  3. Read the Opus clock and channel count.

Fault

The gateway answers with m=audio 19642 RTP/AVP 0. The browser never sends audio.

RFC 8834 says WebRTC endpoints must not send RTP/AVP.

Quiz

DTLS-SRTP keys are established


The SDP proto token for RTP/SAVPF over DTLS with UDP is


WebRTC endpoints must send media with


Required WebRTC audio codecs include


The Opus rtpmap clock and channel count must be


RFC 3389 comfort noise with Opus is


Ecosystem

Glossary, sister systems, and the integration seam for this room.

Analytics Amazon Connect can attach conversational analytics to an external voice system with a SIPREC connector. The analytics plane is not a second SIP proxy for the customer call.

Glossary · Ecosystem map · Ports · Troubleshooting

Sources and go deeper