The example in Table 1 and Table 2 is the same as the one in Transcode G.711 to G.729A and Convert DTMF Inband Tones to RFC2833 but in addition to the transcoding G.711 to G.729A, SBCs must also be prepared for fax calls that are handled with G.711 on Carrier 1 and using T.38 (Fax Relay) on Carrier 2. Either SBCs, or Carrier 2 may detect the fax tone and initiate a modification of its media stream that agrees with the Fax Tone Treatment setting in the SBC's Codec Entry.

Transcode G.711 to G.729A and G711 to T.38 for fax

 

Configuration

Value

Carrier 1 Media G.711 w/Fax
via G.711 Gateway Group GWG1 PSP

Carrier 2 Media G.729A w/Fax
via T.38 IPTG1 PSP

PSP

PSP-Carrier1

PSP-to-Peer

Silence Factor

40

40

Voice Initial Playout Buffer

10

10

TOS

0

184

Data Initial Playout Buffer

50

50

Codec Entry 1

G711-DEFAULT

G729A-DEFAULT - FaxViaT38

Codec Entry 2

<none>

<none>

Codec Entry 3

<none>

<none>

Codec Entry 4

<none>

<none>

AAL Payload Size

47

47

T.38 No. Redundant Packets

1

1

T.38 Low Speed No. Redundant Packets

1

1

T.38 Max Bit Rate

14.4

14.4

Data Rate Mgt Type

Type 2

Type 2

Honor Remote Precedence

Disabled

Disabled

P2P Transcode

Only

Only

Codecs Allowed This Leg

G.711A, G.711U

G.729, T.38

Codecs Allowed Other Leg

(none selected)

(none selected)

RTCP

Not selected

Not selected

Silence Insertion Descriptor

Take defaults

Take defaults

Digit Detect Send Enabled

Not selected

Not selected

Transcode G.711 to G.729A and G.711/T.38 for Fax Codec Entries

 

Configuration

Value
G711-DEFAULTG729A-DEFAULT
FaxViaT38

Audio Encoding

 G.711

 G.729A

Fax Tone Treatment

 <none>

 Fax Relay

Packet Size

 10 ms

 10 ms

Fax Treatment Failure Handling

 Continue

 Continue

G.711 Law

 Law from other leg

 

Modem Tone Treatment

 None

 None

Modem Treatment Failure Handling

 Continue

 Continue

DTMF Relay

 None

 None

 

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