Overview
Transcoding is a process that converts a media stream encoded with one algorithm to another using Digital Signal Processors (DSPs). For example, a media stream encoded using OPUS may be decoded and re-encoded (transcoded) using G.711.
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In high availability configurations, checkpoint for transcoded calls require both the standby system and its DSPs to be ready when a call begins. Calls that are set up before the standby resources are ready will not be maintained on failover. |
LTI based Transcoding
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Internal API is used to access Digital Signal Processor (DSP) resources for transcoding.
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Transcoding resources (DSPFARM) and CUBE must be on the same platform.
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Only DSPFARM profile configuration is required. Skinny Client Control Protocol (SCCP) configuration is not required.
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No TCP socket is opened and no registration is used.
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DSPFARM profile is associated to application type CUBE. Device(config)# dspfarm profile 1 transcode Device(config-dspfarm-profile)# associate application CUBE
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DSPs are not used for encryption with IOS XE. As all media is encrypted or decrypted as it leaves or enters the platform, transcoding may be used for any combination of RTP-RTP, RTP-SRTP, or SRTP-SRTP calls.
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The following support LTI-based transcoding:
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Limitations
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Video transcoding is not supported. This document only refers to transcoding for CUBE B2BUA calls. Refer to System Configuration Guide for Cisco Unified Communications Manager for UCM MTP details.
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SCCP-based transcoding is not supported with IOS XE releases.
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Transcoding cannot be used for SRTP-Passthrough calls or when pass-thru content SDP is enabled.