Coding Video

11Implementation and Performance

11.1 Introduction

This book has examined in detail how video codecs work. An important consideration for practical video codecs is the trade‐off between compression, video quality and computation. A video coding standard, such as H.264 or H.265, provides a set of available coding tools, which are specified in the profiles that are defined in each standard. The actual performance of a video codec, even when it conforms to a standard, depends very much on how it is implemented in software or hardware, as well as on the decisions taken by the video encoder. Different applications can and often do require different encoding and/or implementation strategies. Compare the following for some examples where these might be required:

• Two‐way video calling or video conferencing, such as FaceTime, Zoom and Teams, requires low‐delay, reliable video transmission, with encoding and decoding taking place simultaneously and in real time at both ends of the call. Minimising both end‐to‐end delay and computational cost may be more important than maximising video quality. Video encoding and decoding have to be carried out within the constraints of consumer devices, such as processing power and memory limitations.
• When streaming a popular TV show to an international audience, the same coded video clip is going to be transmitted and decoded perhaps many millions of times. During encoding, it may be more important to maximise video quality and minimise coded bitrate, ...