Restrictions for Audio RTP Passthrough

When Audio RTP Passthrough is enabled for Onsite Proxy, audio streams between IP phones registered to Yeastar P-Series Software Edition via the Onsite Proxy are transmitted directly (peer-to-peer), bypassing both the PBX and the Onsite Proxy. However, this feature does not work in certain scenarios and restricts certain operations as well. This topic describes the detailed restrictions for Audio RTP Passthrough feature.

Invalid scenarios

In the following calls, Audio RTP Passthrough feature does not work even if it is enabled for Onsite Proxy, and audio streams of extensions registered via the Onsite Proxy are still relayed by the PBX.
  • Conference calls.
  • Paging group calls.
  • Video calls.
  • Calls established via the feature code of attended transfer.
  • Calls with recording enabled.
  • Calls monitored by another party.
  • Calls where the two parties share no common codec.

Imposed limitations

Enabling Audio RTP Passthrough feature for Onsite Proxy will limit the following operations. This section provides examples of these limitations and their corresponding solutions.

DTMF mode
For an extension registered via the Onsite Proxy with Audio RTP Passthrough feature enabled, its DTMF mode is automatically switched to Info. When Audio RTP Passthrough feature for the Onsite Proxy is disabled, the mode automatically switch to RFC4733 (RFC2833)。
Note: If the DTMF mode is manually changed to any value other than Info while Audio RTP Passthrough is enabled, the passthrough feature does not work.
Feature Code
  • For extensions registered via the Onsite Proxy with Audio RTP Passthrough feature enabled, dialing a single feature code can not trigger the corresponding action.

    The extension users can append a # symbol after the single feature code to perform desired action.

    Example:

    By default, the extension users can dial *4 to pick up colleagues' calls remotely; but with Audio RTP Passthrough enabled, dial *4# instead.

  • For extensions registered via the Onsite Proxy with Audio RTP Passthrough feature enabled, to successfully perform a blind transfer or an attended transfer via feature code, the extension users must dial the feature code and the number of called party continuously as a single string.

    Example:

    By Default, to perform a blind transfer, the extension users need to dial the feature code *03, wait for a tone, and then enter the number of called party (e.g., 1000); But with Audio RTP Passthrough enabled, dial *031000 all at once instead.