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Audio Codec Support

This section summarize audio codec support with and without (pass-through) transcoding selectable on the SBC Core.

Audio codec relay is supported in SIP-SIP, SIP-H.323 and H.323-H.323 interworking calls.

Note

The SBC SWe does not support transcoding the following codecs:

  • EFR
  • G.722.1
  • T.38

Audio Codecs Supported (Transcoding and Pass-Through)

The SBC Core supports the following narrowband (NB) and wideband (WB) audio codecs for transcoding and pass-through:

Table : Audio Codecs Supported (Transcoding and Pass-Through)

(PSX) Codec Selections

NB / WB

Coding Rates
(Kbps)

Packetization Periods
(ms)

AMR-Bandwidth Efficient

NB

Variable - mix of 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.20, 12.20

20, 40, 60, 80

AMR-Octet Aligned

NB

Same for all AMR

20, 40, 60, 80

EFR

NB

12.2

20, 40, 60
EVRCNB

Variable (171, 80, or 16 bit samples per 20 ms)

20, 40, 60

EVRC0

NB

Variable (171, 80, or 16 bit samples per 20 ms)

20

EVRCB0

NB

4.8, 5.8, 6.2, 6.6, 7.0, 7.5, 8.5, 9.3

20
EVRCBNB

Variable (171, 80, 40, or 16 bit samples per 20 ms)

20, 40, 60

G.711

NB

64

10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60

G.711 with Silence Suppression

NB

64

10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60

G.722

WB

48, 56, 64

10, 20, 30, 40

G.722.1

WB

16, 24, 32

20, 40, 60, 80

G.722.2 (AMRWB-Bandwidth Efficient)

WB

6.6, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05, or 23.85

20, 40, 60, 80, 100

G.722.2 (AMRWB-Octet Aligned)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.723.1

NB

5.3, 6.3

30, 60, 90, 120, 150

G.723.1A

NB

5.3, 6.3

30, 60, 90, 120, 150

G.726

NB

32

10, 20, 30, 40

G.726 with Silence Suppression

NB

32

10, 20, 30, 40

G.729A (compatible with G.729)

NB

8

10, 20, 30, 40, 50, 60

G.729A+B

NB

8

10, 20, 30, 40, 50, 60
iLBC, iLBC-SSNB15.220, 40, 60
NB13.330, 60
OpusNB and WB
  • 6 to 20 (transcoded)
  • 6 to 510 (pass-through)

10, 20, 30, 40, 50, 60

T.38 (version 0)

N/A

up to 14.4

 
T.38 (version 3)N/Aup to 33.6 

Audio Codecs Supported (Pass-Through Only)

The SBC Core supports the following narrowband (NB) and wideband (WB) audio codecs for pass-through:

Table : Audio Codecs Supported (Pass-Through Only)

(PSX) Codec Selections

NB / WB

Coding Rates
(Kbps)

Packetization Periods
(ms)

AMR-CRC

NB

Same for all AMR

20, 40, 60

AMR-CRC Robust Sorting

NB

Same for all AMR

20, 40, 60

AMR-CRC-Interleaving-Robust Sorting

NB

Same for all AMR

20, 40, 60

AMR-Interleaving

NB

Same for all AMR

20, 40, 60

AMR-Interleaving-Robust Sorting

NB

Same for all AMR

20, 40, 60

AMR-Robust Sorting

NB

Same for all AMR

20, 40, 60

Broadvoice

NB (16 Kbps)

WB (32 Kbps)

16, 32

5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60

Broadvoice with FEC

WB

32

15, 20, 25, 30, 35, 40, 45, 50, 55, 60
Dolby DVC-2/8000NB8220

EVRC1

NB

Variable (171, 80, or 16 bit samples per 20 ms)

20, 40, 60

EVRC1 FR

NB

8.55

20, 40, 60

EVRCB1

NB

Variable (171, 80, 40, or 16 bit samples per 20 ms)

20, 40, 60

EVRCB1 FR

NB

8.55

20, 40, 60

G722 with Silence Suppression

WB

48, 56, 64

10, 20, 30, 40

G.722.2 (AMRWB-CRC)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB-CRC-Interleaving)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB-CRC-Robust Sorting)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB- CRC-Interleaving-Robust_Sorting)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB-Interleaving)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB-Interleaving-Robust Sorting)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.722.2 (AMRWB-Robust Sorting)

WB

Same for all AMR-WB

20, 40, 60, 80, 100

G.728

NB

16

10, 20, 30, 40, 50, 60, 70, 80,

90, 100, 110, 120, 130, 140, 150

G.728 with Silence Suppression

NB

16

10, 20, 30, 40, 50, 60, 70, 80,

90, 100, 110, 120, 130, 140, 150

GSM (full rate)NB13.220, 40, 60

iSAC HD codec (pass-through and direct media)

WB

10 to 32

30, 60

L16

NB

128

5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60
MS-RTA

NB (8 Kbps)

WB (16 Kbps)

8, 1620, 40, 60
SILK

NB (8 Kbps)

MB (12 Kbps)

WB (16 Kbps)

SWB (24 Kbps)

8, 12, 16, 2420, 40, 60, 80, 100

Speex

NB (8 Kbps)

WB (16 Kbps)

SWB (32 Kbps)

8, 16, 32

20, 40, 60

Speex with FEC

NB (8 Kbps)

WB (16 Kbps)

8, 16

20, 40, 60

The SBC selects codecs on a call-by-call basis, and negotiates codec use with destination gateway during initial call setup. The SBC also renegotiates the media during a call. The SBC defines configuration parameters such as audio codec, packet size, and TOS to apply to individual call legs.

For direct media connections, bandwidth and policing requirements do not apply. Audio streams must have different IP port numbers, but may have the same or different remote IP addresses. Audio streams for each call leg can be allocated on the same or different IP interface.

Opus Codec Support

Note

Opus transcoding is not supported on SBC 5100 and SBC 5200 platforms.

The SBC 5110, SBC 5210, SBC 5400, SBC 7000, and SBC SWe platforms support the Opus audio codec in accordance with RFC 6716 and draft-ietf-payload-rtp-opus-01 (refer to Supported Standards page). There are no licensing requirements for this codec.

Opus is an open, royalty-free, highly versatile audio codec consisting of a combination of SILK (LPC) and CELT (Constrained-Energy Lapped Transform) codecs. At any given point of time the LP layer, the MDCT (CELT) layer or both may be active. Opus is used for the following applications:

  • VoIP and video conferencing
  • Music/video streaming and storage
  • Remote music jamming
  • Wireless speakers/headphones/microphone
  • Audio books
  • Virtualization/sound servers

Supported Opus Features

The SBC platforms include the following Opus functionality:

  • Input sampling rates of 8k Hz (NB) and 16k Hz (WB) are supported on the IDP interface (encoder input and decoder output)
  • Opus-to-Opus pass-through calls
    • Encoding output bandwidths of 8, 12, 16, 24 and 48 kHz
    • 6 kbps to 510 kbps bit rates
  • Opus transcoded calls
    • Max bandwidth of 16 kHz
    • Max bit rate of 20 kbps
  • Mono mode for both pass-through transcoded calls
  • Stereo mode for Opus-to-Opus pass-through.
  • Inband FEC mode
  • Variable bit rate (VBR)
  • DTX mode
  • Single channel mode is supported
  • Fax/Modem tone (FMTD) detection is not supported in Opus leg
  • DTMF (Inband DTMF detection is not guaranteed)

On SBC SWe, Opus DTX is fully supported on both transmitter and receiver sides; however, packets are generated approximately every 200 milliseconds during DTX period.

 

Note

The following Opus attributes cannot be controlled by the operator:

  • Maxplaybackrate
  • Sprop-maxcapturerate
  • Stereo
  • sprop-stereo

UXPAD Operational Modes

As with other currently-supported compression codecs, the SBC supports Opus in UXPAD only. The following UXPAD operational modes are supported by the SBC:

  • WB to WB transcoding using two UXPADs connected back to back over IDP-WB format. The wideband voice features should be preserved while performing the transcoding in two stages using PADs, the intermediate IDP should always be wideband.
  • WB to NB transcoding (except for G.711-RTP) using two UXPAD connected back to back over IDP-NB format.
  • WB to G.711-RTP transcoding using single UXPAD.
  • Opus to TNAPAD to play out any tones or announcements.
  • Opus-to-Opus transcoding using two UXPADs connected back-to-back over IDP-WB format. This is used only for Opus-to-Opus transcoding that may occur due to existing Packet Service Profile (PSP) flags:
    • Transcode always
    • Conditional Transcoding > Conditions in addition to “No common Codec”:
      • Different ptime/Silence Suppression,
      • Different DTMF relay.

Note

Any up-sampling or down-sampling may introduce some noise and degrade speech quality. In addition, wideband speech quality is lost if down-sampling is done for wideband-to-narrowband transcoding. However, up-sampling / down-sampling is required for interworking

Figure : UXPAD Support of Opus

DTX and Inband FEC Support

The SBC Core supports DTX on the transmitter side and Inband FEC on the transmitter and the receiver side for Opus codec. The following parameters support this feature:

ParameterBehavior
Maxaveragebitratemin (offer/answer of peer, route PSP, 20kbit/s)
Useinbandfecmin (offer/answer of peer, route PSP)
usedtxmin (offer/answer of peer, route PSP)
usecbrConstant bit rate if either peer requests cbr=1 OR route is configured for cbr=1