4.2.5. Setting Coder Information

Terminal capabilities are exchanged as part of the H.245 session used during call establishment. The terminal capabilities are sent to the remote side as notification of coder supported.

The terminal capability list for the system is set in the config.val file and is configured at firmware download time. See the IPLink User's Guide for more information.

Table 7 shows the coders that are supported when using Global Call with a DM3 board that uses an embedded stack.

Table 7. Coders Supported by the Global Call API 

Coder and Rate	Global Call # Define	Frames Per Packet (fpp) or Frame Size (ms)	VAD Support
G.711ALaw	GCCAP_AUDIO_g711Alaw64k	Frame Size: 10, 20, or 30 ms(Frames Per Packet: Fixed at 1 fpp)	Not applicable
G.711ULaw	GCCAP_AUDIO_g711Ulaw64k	Frame Size: 10, 20, or 30 ms(Frames Per Packet: Fixed at 1 fpp)	Not applicable
G.723.1 5.3 Kbps	GCCAP_AUDIO_g7231_5_3k	Frames Per Packet: 1, 2 or 3 fpp(Frame Size: Fixed at 30 ms)	Enabled (default) or disabled
G.723.1, 6.3 Kbps	GCCAP_AUDIO_g7231_6_3k	Frames Per Packet: 1, 2 or 3 fpp(Frame Size: Fixed at 30 ms)	Enabled (default) or disabled
G.729A	GCCAP_AUDIO_g729AnnexA	Frames Per Packet: 3 or 4 fpp(Frame Size: Fixed at 10 ms)	Not applicable
G.729A with AnnexB	GCCAP_AUDIO_g729AnnexAwAnnexB	Frames Per Packet: 3 or 4 fpp(Frame Size: Fixed at 10 ms)	Not applicable (VAD is supported implicitly)
GSM FR	GCCAP_AUDIO_gsmFullRate	Frames Per Packet: 1, 2 and 3 fpp(Frame Size: Fixed at 20 ms)	Disabled (default) orEnabled
Note: For G.711 coders, the frame size value (not the frames per packet value) is specified in the frames_per_pkt field of the IP_AUDIO_CAPABILITY structure. See Section 7.1, "IP_AUDIO_CAPABILITY" for more information.

Coder information can be set in the following ways:

• On a system wide basis using gc_SetConfigData( ).
• On a line device basis using gc_SetUserInfo( ) with a duration parameter value of GC_ALLCALLS.
• On a call basis using gc_MakeCall( ) or gc_SetUserInfo( ) with a duration parameter value of GC_SINGLECALL.

In each case, the following parameter set ID and parameter IDs are used to set up a GC_PARM_BLK containing the coder information:

• GCSET_CHAN_CAPABILITY
  • IPPARM_LOCAL_CAPABILITY - a parameter of type IP_CAPABILITY

Possible values for fields in the IP_CAPABILITY structure are:

• capability - One of the following:
  • GCCAP_AUDIO_g711Alaw64k
  • GCCAP_AUDIO_g711Ulaw64k
  • GCCAP_AUDIO_g7231_5_3k (at 5.3 kbits/s)
  • GCCAP_AUDIO_g7231_6_3k (at 6.3 kbits/s)
  • GCCAP_AUDIO_g729AnnexA
  • GCCAP_AUDIO_g729AnnexAwAnnexB
  • GCCAP_AUDIO_gsmFullRate
• type - GCCAPTYPE_AUDIO
• direction - One of the following
  • IP_CAP_DIR_LCLTRANSMIT - transmit capability
  • IP_CAP_DIR_LCLRECEIVE - receive capability
• payload_type - Not supported.
• extra - Must be of type IP_AUDIO_CAPABILITY.
  • extra.frames_per_packet - The number of frames per packet.

    Note: For G.711 coders, this field is the frame size (in ms), which must be one of the following values only: 10, 20, or 30.

  • extra.VAD - 0 (disabled) or 1 (enabled)

See Section 7.2, "IP_CAPABILITY" for more information.

The application can retrieve information about the transmit coder that the remote side used (see Section 4.3, "Retrieving Current Call-Related Information"), but the application cannot get a list of supported coders once a call has been answered.

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