There are many forms of IPTV (Internet Protocol Television), and industry have been debating just exactly what IPTV constitutes. Web TV in the form of played out video or live TV uses a web server to distribute the media which is accessible via a web browser. This is often referred to as Over the Top TV as it is TV delivered using the existing Internet infrastructure. One of the major challenges for this form of IPTV is to maintain QoS (Quality of Service) or QoE (Quality of Experience). VOD (Video on Demand is another area of IPTV delivery where users select a video stream for delivery on demand and don’t just tune in to an already running channel.
The United Kingdom recently completed the switchover to digital from existing analogue systems for broadcast TV services. If this type of broadcast service is to be delivered using an IP networks, then that network needs to be extremely well engineered and managed if subscribers are to receive consistent quality. If the goal is to deliver HDTV (High Definition Television) over IP then that network will need to use high quality hardware in terms of streamers, video encoders, routers and switches, not to mention a professional management and monitoring system.
One major challenge is in transcoding TV formats including PAL, SECAM and NTSC and digital compression formats such as MPEG-2 and MPEG-4. The DVB (Digital Video Broadcast) standards developed in Europe is a suite of open standards defining delivery methods for digital broadcast television. The standards are maintained by a European consortium of 100s of members under the auspices of ETSI (European Telecommunications Standards Institute). Although there are many standards, these standards fall into 3 main categories:
- DVB-T is the main standard for digital terrestrial television.
- DVB-S is the group of standards for digital television over satellite.
- DVB-IPI, or sometimes commonly referred to as IP over DVB or IP over MPEG utilises Internet Protocol for the delivery of MPEG transport streams, and has become the common method employed by major IPTV vendors.
If VoD (Video on Demand) is the aim then a VoD server containing the digital files will be positioned in the network to allow customers to access streams when required. With this type of service, the VoD server should be positioned as near to the Access Layer of the network as possible to reduce the impact of multiple duplicate streams on the Core Network. Often when the video stream is demanded it is downloaded into a local set top box for playout or can be streamed and played direct from a VoD server even in near real time. Live TV often uses IP Multicasting techniques to ensure the distribution of the available channels to all areas of the Access Network via the Core Network.
An IP network that distributes commercial TV services needs to be designed to be extremely reliable to guarantee the service at all times. Any failures need to be recovered quickly and efficiently, which is achieved through redundancy and switching of network components through the use of SNMP (Simple Network Management Protocol). Redundancy can be achieved through the use of HSRP (Hot Standby Router Protocol) or VRRP (Virtual Router Redundancy Protocol). Commercial broadcast services utilising IP networks will normally require that the streamers will fixed source IP addresses and the user equipment such as set top boxes will have the media streams mapped to IP Multicast groups. The network will be employing IP Multicast routing protocols such as PIM (Protocol Independent Multicast) to ensure efficient delivery of the streams to the Access Network from the Service Provider Headend.
Service providers and media companies are quickly deploying the new IPTV services and in the UK the major players in this market are BT with their BT Vision offering and TalkTalk with TalkTalk TV. These services are delivered using broadband internet and the ADSL standards.