Broadcast TV has set a high bar for viewer expectations and delivering a great quality of experience. As the trend and demand for multiscreen viewing and TV Everywhere continues to grow so does the demand for a high quality experience regardless of the device being used. Behind that multiscreen experience lies some complex adaptive bit rate (ABR) technology and a new set of monitoring challenges.
To give content providers visibility into their content and let them rapidly identify and address issues that impact user experience requires a sophisticated set of monitoring and analysis tools. Those tools need to provide comprehensive insights into both the quality of experience (QoE) and quality of service (QoS) on the delivery network being employed. These systems need to check everything from validating the availability of the assets to determining the quality of those assets even if they are encrypted.
ABR provides a mechanism for real-time and continuous display of video no matter how much or how little bandwidth is available on the device being used. It does this by fragmenting or packaging the content into small 2- to 10-second segments with several profiles (the same content at different bit rates) and then delivering the correct sequence of fragments at a bit rate that suits the available bandwidth. This means that to deliver a constant stream of content that does not falter the quality of the video will vary according to bit rate and available bandwidth. To be sure, the higher the bit rate the better the quality of experience, but most importantly as long as some bandwidth is available the video will keep playing.
Any ABR system works by actively measuring the latency, available bandwidth, and how full the playout device buffer is. If it is becoming full, the client device requests a lower bitrate profile. As the buffer empties the device requests a higher bitrate profile.
Figure 1 illustrates the key principles behind this. In this particular example the segments are occurring on 2 second boundaries and it shows the seamless transition of the content on a device as it moves between different profiles. The same thing could happen on a single device as it moves between different networks and the overall available bandwidth varies, such as when switching between a Wi-Fi network and a cell phone network.
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