In the Groove
French Commercial Station TF1 switches HD-SDI Audio with NEXUS

The TF1 installation demonstrates that handling SDI audio really can be simple and convenient - provided the appropriate components are selected! The new NEXUS XHDI board for HD-SDI offers a plethora of functions.

French commercial TV station TF1 is currently undertaking a gradual modernisation of their main switch room, with an emphasis on SDI and HD. In this respect, TF1 is not only in tune with the current trends in connectivity, but is also ridding itself of yet another unpleasant problem. Undesirable audio to video latency differences are now a thing of the past because both types of data are always routed simultaneously. Today, the station’s interface with the outside world consists of new HD-enabled SDI matrices. These feed signals from OB vehicles and other external sources into the in-house network.

XHDI in Bulk

Routing audio and video in SDI format simultaneously involves a few limitations currently because a pure SDI solution would only have been achievable at the cost of flexibility. At TF1 this potential shortcoming has been eliminated in an elegant manner by using the NEXUS as an interface between video and audio. With around 110 NEXUS High Definition SDI boards, the so-called XHDI boards, this set-up is also the largest ever HD-SDI audio installation based on STAGETEC components.
The NEXUS XHDI boards can de-embed all of the 16 supported audio tracks from the SDI stream, process them, and re-embed them into the same frame. Thus, in contrast to the four or eight audio tracks per SDI signal currently used in broadcasting, the NEXUS board offers the full complement of tracks as specifi ed by the standard. Why? Because an investment into a key component such as the main switch room is highly critical and future proofing is therefore of paramount importance.

Standard and High Definition

NEXUS XSDI boards, which support standard resolution SDI, have been available since 2003. About a year ago, STAGETEC introduced the HD-enabled XHDI version. It is backward compatible and therefore also processes standard resolution SDI. In addition to de-embedding and embedding, the board also supports so-called replacement functions. These enable the channel assignment in an SDI signal to be altered. Dolby-E encoded signals also present no problem for the Dolby-certified NEXUS. Such signals are transparently forwarded and can be embedded into an SDI signal or de-embedded from it. XHDI is also the right choice wherever multichannel-audio transmission to separate audio tracks without Dolby E encoding is required. It ensures that all audio blocks defi ned in the SDI format will experience identical latencies, thus preventing phase shifts between tracks in different blocks.
The XHDI board can be equipped with sample-rate converters just like any other NEXUS digital audio board. This enables audio to be de-embedded and re-embedded even to and from asynchronous SDI input signals.
Every XHDI board offers a single video input plus two video outputs carrying the same signal. This feature set enables video signals to be forwarded without the use of extra hardware and even provides a split feed. Yet that’s not the whole connectivity story: The XHDI is equipped with both BNC and optical interfaces. This means that the XHDI also supports conversion between BNC and optical formats.

Just the Beginning …

Redesigning the main switching room at TF1 is just the first step in an extensive renovation process. Conversion of the production studios to HD will follow. The NEXUS network, including the HD-SDI interfaces, is the corner stone of this transition to HD - with generic audio functions and fl exible embedding of any audio stream on the NEXUS into any SDI stream.
Incidentally, the NEXUS installation at TF1 is also leading the way where in service reliability standards are concerned. The network with its dual-star topology comprising two NEXUS STARs and five Base Devices forms a stable basis for an extremely powerful audio installation with a high level of redundancy.