Broadcast Beat Magazine 2017 IBC Show - Page 82

the inherent lack of correlation. Many of the issues that can cause problems in IP networks can be traced back to packet jitter. Excessive packet jitter can lead to buffer overflows and underflows causing dropped packets and stalled data flows. Other problems stem from tim- ing delay and asymmetry of PTP packet flows. In hybrid SDI and IP workflows, it is also necessary to ensure that the relationship between the SDI and IP video is consistent to enable seamless frame accurate switching. For a successful and seamless deployment of an IP-based broadcast infrastructure, interoperability testing of equipment from various ven- dors in the network is also of utmost important. To achieve that, the IP test and measure- ment instruments need to sup- port the latest IP standards as they are adopted by the indus- try. Since IP video technology and standards are still evolving, the IP monitoring equipment needs to be easily upgradeable to keep up with the changes as well. Therefore, it’s important to select hybrid IP test gear with a software-based architecture so it can keep pace with the rapid pace of change. Figure 1: Time-correlated video and IP errors are key to understanding if impairments are being caused by IP errors. Figure 2. Traditional video monitoring and audio bars are useful in confirming errors. EFFICIENT TROUBLE- SHOOTING Successful deployments of hybrid and all-IP infrastructure for video will require the ability to establish root causes quickly and efficiently. The first step is to understand whether visible impairments are being caused by IP errors or if some other fault is causing the impairments. Figure 3. Measuring the time relationship between black burst/tri-level sync and PTP. Figure 1 shows how a network- monitoring tool can be used to track time-correlated video and IP errors. This is made possible by correlating the time stamps of video errors and packet 82 • Broadcast Beat Magazine • www.broadcastbeat.com errors. A video CRC error, however, does not in itself confirm that the video is impaired making it desirable to use traditional monitoring methods such as picture and waveform displays