Transcoding Introduction
Transcoding is the ability to convert between media streams that are based upon disparate codecs. The Oracle Communications Session Border Controller supports IP-to-IP transcoding for SIP sessions, and can connect two voice streams that use different coding algorithms with one another.
This ability allows providers to:
- Handle the complexity of network connections and the range of media codecs with great flexibility
- Optimize bandwidth availability by enforcing the use of different compression codecs
- Normalize traffic in the core network to a single codec
- Enact interconnection agreements between peer VoIP networks to use approved codecs
By providing transcoding capabilities at the network edge rather than employing core network resources for the same functions, the Oracle Communications Session Border Controller provides cost savings. It also provides a greater degree of flexibility and control over the codec(s) used in providers’ networks and the network with which they interconnect.
In addition, placing the transcoding function in the Oracle Communications Session Border Controller and at the network edge means that transcoding can be performed on the ingress and egress of the network. The Oracle Communications Session Border Controller transcodes media flows between networks that use incompatible codecs, and avoids back-hauling traffic to a centralized location, alleviating the need for multimedia resource function processors (MRFPs) and media gateways (MGWs) to support large numbers of codecs. This maximizes channel density usage for the MRFPs and MGWs so that they can reserve them for their own specialized functions.
Transcoding Hardware
A transcoding Network Interface Unit ( NIU) provides the DSP resources that enable transcoding on the Oracle Communications Session Border Controller.
- The Acme Packet 6300 and Acme Packet 4600 can accept 1-24 transcoding modules to provide increasing transcoding capacity.
Transcoding Capacity
Transcoding capacity depends on the following:
- Codecs used for transcoding
- Number of transcoding modules installed in the system. Capacity scales linearly with each extra transcoding module installed.
Transcodable Codec Details
The following table lists the supported codecs, bit rates, RTP payload type, default ptime, and supported ptimes.
| Codec | Supported Bit Rate (kbps) | RTP Payload Type | Default Ptime (ms) | Supported Ptime (ms) |
|---|---|---|---|---|
| G.711 PCMU | 64 | 0 | 20 | 10, 20, 30, 40, 50, 60 |
| G.711 PCMA | 64 | 8 | 20 | 10, 20, 30, 40, 50, 60 |
| G.722 | 48, 56, 64 | 9 | 20 | 10, 20, 30, 40 |
| G.723.1 | 5.3, 6.3 | 4 | 30 | 30, 60, 90 |
| G.726 | 16, 24, 32, 40 | 2, 96-127 | 20 | 10, 20, 30, 40, 50 |
| iLBC | 13.33 | 96-127 | 20 | 20, 30, 40, 60 |
| 15.2 | 96-127 | 30 | 20, 30, 40, 60 | |
| G.729/A/B | 8 | 18 | 20 | 10, 20, 30, 40, 50, 60, 70, 80, 90 |
| AMR | 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, 12.2 | 96-127 | 20 | 20, 40, 60, 80, 100 |
| AMR-WB (G.722.2) | 6.6, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05, 23.85 | 96-127 | 20 | 20, 40, 60, 80, 100 |
| GSM FR | 13 | 3 | 20 | 20 |
| T.38 | 4.8, 9.6, 14.4 | N/A | 10, 20, 30 |
| Codec | Supported Bit Rate (kbps) | RTP Payload Type | Default Ptime (ms) | Supported Ptime (ms) |
|---|---|---|---|---|
| EVRC | 0.8, 4.0, 8.55 | 96-127 | 20 | 20, 40, 60 |
| EVRC0 | 0.8, 4.0, 8.55 | 96-127 | 20 | 20 |
| EVRC1 | 4.0, 8.55 | 96-127 | 20 | 20, 40, 60, 80, 100 |
| EVRCB | 0.8, 2.0, 4.0, 8.55 | 96-127 | 20 | 20 |
| EVRCB0 | 0.8, 2.0, 4.0, 8.55 | 96-127 | 20 | 20 |
| EVRCB1 | 4.0, 8.55 | 96-127 | 20 | 20, 40, 60, 80, 100 |
| Opus | 48 | 104 | 20 | 10, 20, 40, 60, 80, 100 |
| SILK | 8, 16 | 103 | 20 | 20, 40, 60, 80, 100 |
