Asterisk - The Open Source Telephony Project  GIT-master-a24979a
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: URLs and web pages
  • MODEM: Modulated data encodings, such as T.38 and V.150
  • IAX: Private frame type for the IAX protocol
  • CNG: Comfort noise 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

  • HANGUP The other end has hungup
  • RING Local ring
  • RINGING The other end is ringing
  • ANSWER The other end has answered
  • BUSY Remote end is busy
  • TAKEOFFHOOK Make it go off hook (what's "it" ? )
  • OFFHOOK Line is off hook
  • CONGESTION Congestion (circuit is busy, not available)
  • FLASH Other end sends flash hook
  • WINK Other end sends wink
  • OPTION Send low-level option
  • RADIO_KEY Key radio (see app_rpt.c)
  • RADIO_UNKEY Un-key radio (see app_rpt.c)
  • PROGRESS Other end indicates call progress
  • PROCEEDING Indicates proceeding
  • HOLD Call is placed on hold
  • UNHOLD Call is back from hold
  • VIDUPDATE Video update requested
  • SRCUPDATE The source of media has changed (RTP marker bit must change)
  • SRCCHANGE Media source has changed (RTP marker bit and SSRC must change)
  • CONNECTED_LINE Connected line has changed
  • REDIRECTING Call redirecting information has changed.