Asterisk.org: Developer Documentation (28 Oct 2009)

Wed Oct 28 15:49:24 2009

## Asterisk developer's documentation

# 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
  - HTML: URL's and web pages
  - T38: T38 Fax transport frames
  - 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

Files
  - frame.h Definitions
  - frame.c Function library
  - Asterisk Channels Asterisk channels

## 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