Knowledge

Testing Broadcast Applications with Impairments

Serial Digital Interface (SDI) has, until recently, been the preferred transport mechanism for broadcast transmission. Its main advantage is that it provides a consistent and predictable delivery of data which is ideal for audio/video transport. However, networks in the broadcast industry are now in a state of flux. Increasingly there is a shift away from single-purpose legacy systems like SDI, and a shift towards multi-purpose IP-based networks. The change has come about due a variety of reasons, including:

  • Ubiquity of IP networks and infrastructure.

  • Wider expertise in general IP-focused networking, therefore less specialist training required.

  • Multi-purpose equipment can be redeployed or change of use.

  • Broader choice of components.

  • Smaller size of equipment reduces the hardware footprint in the data centre.

While these are valid reasons for the move to IP, it’s not without challenges. Foremost among these is that IP networks bring an unpredictability and inconsistency of performance. In real terms this means elements such as latency, jitter and packet loss now impact on data transmission in ways that were not experienced in the SDI world. Video is particularly sensitive to such conditions and risks Quality of Service (QoS) unless appropriate steps are taken.

Influence of SMPTE

The Society of Motion Picture and Television Engineers (SMPTE) plays an active role in this regard. They continue to define new standards to allow for the increased adoption of IP-based networks for broadcast. The standards set out a framework of best practices that allow for successful deployments of new networks. The SMPTE are also more vocal in demanding conformance to the standards.

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