What is lip sync, and why is it important?

What is lip sync, and why is it important?

What is lip sync, and why is it important? Lip sync is one of the new specifications for HDMI 1.3. First we need to understand what HDMI is and how lip sync correlates.

High Definition Multimedia Interface is the only uncompressed, all digital audio/video interface that is supported by the industry. Founders of HDMI include manufacturers of leading consumer electronics Panasonic, Phillips, Hitachi, RCA, Sony, Toshiba, and Silicone Image. HDMI is also supported by motion picture producers Universal, Fox, Disney, and Warner Brothers, as well as system operators EchoStar and DirecTV. High Definition Multimedia Interface provides an interface in between any video/audio source, like an A/V receiver, digital television, and DVD player over one cable total, instead of one cable for video and one cable for audio. HDMI will support high definition video, standard video, and / or enhanced video plus multiple channels of digital audio on one single cable. HDMI will also send every ATSC HDTV standard and can support eight channel digital audio. HDMI has plenty of band width to spare so that any future requirements and enhancements can be accommodated.

Each version of the HDMI standard has been developed with forward-advancing capabilities in sight and the standards for HDMI are continuously evolving. Each successive version of the HDMI specification has been created to be backwards compatible with all earlier versions of that specification. This has not always been the case with some of the manufacturers products that were Digital Video Interface (DVI) enabled.

HDMI version 1.3 includes a specification for lip sync capabilities. HDMI 1.3 specifications incorporates an automatic audio syncing, or lip syncing, capability. In a digital television, the video processing usually takes more time than the audio processing. Because of this, synchronization of video and audio can become an issue, if it becomes noticeable to the viewer. This can create an effect that is similar to a badly dubbed movie, where audio and video signals are out of sync. HDMI 1.3 utilizes a method where the audio processing times in the devices can be adjusted automatically to remove errors in lip sync. The 1.3 lip sync correction functionality is needed on the device that creates the lip sync problem, usually a display, which has a lapse between audio/video processing because of the more demanding requirements of video processing, and a device that will correct the lip sync delay. The initial implementations of this will be in a receiver, but this functionality will be in DVD players, and most other CE devices in the future. The reports from manufacturers indicate that this function will be widely implemented and is very popular.

Audio and video synchronization problems occur because video processing is more intensive than audio processing. Because of this, audio is ready for the playback before the video. Without synchronization, what viewers hear won't match what they see on the screen, for example, where the timing of lip movement is off from the words being heard, and this significantly impacts the overall viewing experience. A/V synchronization, also known as lip sync, is maintained by delaying the playback of the audio stream until the video stream has finished processing. The actual delay needed for synchronization will depend upon the type of audio and video signals, and the current video mode.

Synchronization can also play a part in wireless multi-channel speaker applications. Because of the inherent processing delays of wireless transmission, it takes more time for transmitted channels to output audio than non-transmitted channels. The non-transmitted channels, therefore, need an additional delay to synchronize them with transmitted channels.

As television applications become more and more sophisticated, and more wireless components are being adopted, there has developed a real need for lip sync devices in the market that can be easily implemented and that meet the needs of manufacturers.

Lip sync is important to the display industry and consumers because newer technology has created a noticeable delay between the processing of video signals and the processing of audio signals. Lip sync capabilities allow for a processing delay, so that both signals are synchronized together and are output together. This greatly improves the viewing experience for the viewer.