Asterisk - The Open Source Telephony Project  18.5.0
AST Multimedia and signalling frames

What is an ast_frame ?

A frame of data read used to communicate between between channels and applications. Frames are divided into frame types and subclasses.

Frame types
  • VOICE: Voice data, subclass is codec (AST_FORMAT_*)
  • VIDEO: Video data, subclass is codec (AST_FORMAT_*)
  • DTMF: A DTMF digit, subclass is the digit
  • IMAGE: Image transport, mostly used in IAX
  • TEXT: Text messages and character by character (real time text)
  • TEXT_DATA: Text messages in an ast_msg_data structure
  • HTML: URL's and web pages
  • MODEM: Modulated data encodings, such as T.38 and V.150
  • IAX: Private frame type for the IAX protocol
  • CNG: Comfort noice frames
  • CONTROL:A control frame, subclass defined as AST_CONTROL_
  • NULL: Empty, useless frame

Control Frames

Control frames send signalling information between channels and devices. They are prefixed with AST_CONTROL_, like AST_CONTROL_FRAME_HANGUP