2. MPEG-4 systems

The MPEG-4 standard not only saw the development of new tools for coding audio and video, but also new systems (figure 22 ), to enable new functionalities. It is true that an MPEG-2 TS (Transport Stream) data stream can be stored, but it is recorded in the same way as it is transmitted, which inhibits applications such as search. Similarly, with MPEG-2 TS, the protection system is limited to signalling access control and transporting the encrypted "keys" needed to descramble images and sounds. Developments in MPEG-4 systems concern in particular :

• distribution (§ 2.1