Synchronization technologies for broadcasting
For broadcast applications, broadcast stations are investigating the use of set-top boxes (STBs) and video monitors to confirm that they are correctly in sync. Digital broadcasting, however, introduces another complication to the monitoring equation--software. Every digital STB has software running on it. Depending on the implementation of the software
in a specific STB, the receiver may react differently to a specific channel within the signal stream. Therefore, problems that affect users of one type of STB may not be visible to users of another STB brand, or even a later model from the same manufacturer.
Various audio/video synchronization technologies for broadcast currently exist that can analyze, measure and correct lip sync error. One measurement system uses a special test signal that synchronizes a video "flash" and audio tone burst. The two signals can be monitored on an oscilloscope to determine the delay between them.
Several other types of specialized products can correct varying delays automatically, such as the Pixel AD3100 audio delay and synchronizer, which provides compensation based on a control input from a compatible video frame synchronizer. It can also automatically correct independent variable delay sources by interfacing with the company's DD2100 video delay detector, which samples the video at two points in a system and then provides a control signal to the AD3100 audio delay unit.
Similarly, the Sigma Electronics Arbalest system uses a proprietary technology to provide automatic video delay detection and audio compensation in a system.
The JDSU DTS-330 real-time transport stream analyzer with SyncCheck provides lip sync analysis when used with a special video source. The K-WILL QuMax-2000 generates a "Video DNA" identifying signal that can measure the timing of video signals in a plant or even at separate locations.
Figure 2: The Pixel Instruments LipTracker
The Pixel Instruments LipTracker detects a face in the video and then compares selected sounds in the audio with mouth shapes that create them in the video. The relative timing of these sounds and corresponding mouth movements are analyzed to produce a measurement of the lip sync error.
Next: Simplay Labs HD lip sync performance program