IPTV/VoD: Get up to speed
Fast track your knowledge
- IPTV content can be real-time (live) or offline (downloaded). It can also be pushed to a client device (e.g. overnight delivery) or pulled across the network.
- Most ISP and telco networks are based on an old telecoms technology called ATM. The advent of broadband has meant most are upgrading their networks to be IP-based.
- Almost all of the top 10 broadband ISPs in the UK now have a strategy of some kind for providing voice and television to their customers.
- The most practical way for ISPs to enter the television market in the UK is to provide some form of hybrid TV/broadband service that adds a broadband "back channel" and PVR functionality to the Freeview or Freesat digital TV platforms.
- BT's network is ATM-based and does not support multicast. The 21CN upgrade programme will change the UK infrastructure to be IP-based and is expected to be complete just before UK Digital TV Switchover in 2012.
- IPTV video is usually supplied in MPEG-2, MPEG-4 and/or Windows Media (VC-1). The favourite choice is H.264 (MPEG-4 AVC) that can produce DVD-quality video at very low bandwidths (1-3Mbit/s for SD, 6-10Mbit/s for HD). Most need the video to be encapsulated in an MPEG-2 transport stream.
- Most IPTV platforms use open standards and trusted protocols for delivering audio and video in real-time, such as RTP, RTSP, resilient UDP and SAP/SDP.
- A normal 8Mb ADSL connection can theoretically support up to 3 SD IPTV channels or 1 HD channel in MPEG-4, but in practice it is difficult to send more than 1 on either. A DSL connection must usually be 4Mbit/s and above to support a live IPTV broadcast stream and 2Mbit/s for on-demand content.
- Fiber (Gbit/s), Ethernet (100Mbit/s), ADSL2+ (24Mbit/s) and VDSL2 (70Mbit/s+) connections are a more preferable and reliable network speed to deploy IPTV over.
- Video running over IP networks is easily disrupted, so in order to make sure the picture doesn’t break up a network must implement Quality Of Service (QoS) rules that separate voice, video and internet data into their own "channels".
- The internet is a best-effort network and does not have QoS. IPTV provided by ISPs runs across their network but does not reach the internet. QoS is achieved by mapping ATM virtual circuits (VCs) to IP Virtual LAN groups (VLANs).
- An IPTV testing lab or small simulation can be purchased and installed extremely cheaply and easily (less than $10k or £5k) on any office LAN to help cross-train developers and create example software applications (such as menus and screens).
- The net neutrality or two-tier internet debate originated in the USA, and refers to a unilateral policy being adopted by US telcos of charging content providers more for using their network to deliver content than they do themselves.
- It is almost impossible to reliably transmit broadcast video over a wireless (Wi-Fi) network, even if it runs at speeds over 108Mbps. Specialist technologies exist that try to solve this problem.
- The easiest way to connect an IP set-top box to a broadband wire when it can’t be connected by a normal Ethernet cable (i.e. when it is in a different room to a home router) is to use PLC (powerline communication) – 200Mbps Ethernet networking over home electricity power cabling.
- The future of the broadband home is to have embedded PLC technology in all electronic devices, so they are immediately network and internet-enabled when they are plugged into a normal electric power socket in any room in the home.
- Live television must be multicasted over a network, which is the computer equivalent of normal broadcast where only one copy of a TV signal is sent instead of everyone having a personal (unicast) copy. Many networks do not support UDPbased multicast technology, including the internet.
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