WebRTC Metrics
A comprehensive overview of WebRTC statistics, derived indicators, and observable signals, to better understand call quality, connectivity, and user experience in rtcStats
SDP content changed
At least one line in the local SDP was added, removed, or its content changed compared to the offer generated by the WebRTC stack. This alters codec parameters, bandwidth limits, or other negotiation attributes and may cause interoperability issues.
Description
Although modern WebRTC APIs provide higher-level controls, SDP sometimes still needs to be modified manually (SDP munging) to force specific behaviors, such as enabling Opus DTX. However, this practice, while still tolerated by browsers, is fragile and error-prone.
What do we do here?
We compare the SDP passed to setLocalDescription against the SDP produced by the preceding createOffer or createAnswer call. When a line's content differs between the two SDPs - meaning it was added, removed, or its text was changed - we flag the modification.
Unlike line reordering, content modifications directly alter the negotiated session: codec parameters, bandwidth limits, ICE credentials, or extension headers. Incorrect modifications can cause connection failures or degrade media quality. If you see this observation, review the SDP transformations applied by the application before setLocalDescription is called.
