IPTV Delivery Networks

Chapter 5Zapping Delay Reduction in IPTV Systems

Alireza Abdollahpouri

5.1 Introduction

Most TV viewers surf the channels to find a programme of interest. These surfing events happen more frequently during, for example, commercial advertisements or the half-time break of a soccer game.

IPTV service providers use multicast for transmitting TV channels. Due to the lack of network bandwidth in the last-mile access link, not all the channels can be transmitted at the same time. This limitation leads to a delay between two consecutive channel switches. In addition, the dependency between frames in compressed video streams (using e.g., moving picture experts group (MPEG)-2) prevents the ability of random access and prolongs the switching delay.

On the other hand, to make profit and satisfy subscribers, an IPTV service provider has to provide at least the same (if not better) quality of experience (QoE) in comparison with the already existing video delivery schemes (e.g., cable or satellite). The most relevant aspects for QoE are:

• Video and audio quality
• Audio to video synchronisation
• Channel-switching delay (zapping delay)

The time between pushing the channel change button and the first video frame being displayed on the TV along with the corresponding audio is called zapping delay. Channel zapping delay is a fundamental requirement for the user's QoE. Although it seems to be a natural requirement from a subscriber's perspective, providing this functionality can be problematic ...