creasing percentage of viewers quickly notice the disconnect. When the audio is only 40 ms early, already 20% of the viewers notice-any earlier and it rapidly becomes unacceptable, distracting, and annoying. Audio early Audio late UNACCEPTABLE UNACCEPTABLE Percentage who notice 50 ms 100 ms 150 ms 200 ms 250 ms 300 ms 350 ms 400 ms Figure 2-11 Timing Solutions for Circuit Emulation The engineer needs to provide the synchronization between audio and video across the whole range of the creation process: content capture (cameras and SO on), editing, distribution, and broadcast. Similarly, for packet-based A/V distribution to the subscriber-for example, with IPTV and digital video broadcasting (DVB)-the synchronization of audio and video needs to be maintained to the viewing screen (whether it be home, theatres, theme parks, or stadiums). One of the tools used to maintain synchronization is based upon another PTP profile known as ST2059-2 from the Society of Motion Picture and Television Engineers (SMPTE). Also commonly used in the timing role for A/V is another profile of PTP known by the Institute of Electrical and Electronics Engineers (IEEE) standards number 802.1AS. There is also another profile from the Audio Engineering Society (AES), known as AES67, which is also used for audio processing. More information on the SMPTE and AES organizations and profiles is provided in Chapter 4 and Chapter 7. 2.3 Industrial Uses of Time-Power Industry In addition to the previously mentioned examples, there are many other uses of synchronization, such as in industrial automation and mechanical processes. The use of multiple robots and machines in a factory assembly line is one common example of time synchronization, and the first standard- ized version of PTP was designed for industrial cases. It is worth outlining another use case as a practical example to demonstrate that distributing timing across a wide area is not only a 5G or even a mobile problem. In fact, many of the same issues that arise when designing timing in mobi