audio/videoZONE Products for the week of July 10, 2006
Texas Instruments Says . . .
TPA5050: Audio Delay IC For Lip Sync Correction
Configurable Lip Sync Delay with 170 ms per Channel
Dedicated to minimizing design complexity, while reducing system cost, Texas Instruments Incorporated (TI) has introduced the TPA5050 digital audio delay with IIC control. Designed for high definition and flat panel TV applications, the TPA5050 digital audio delay provides cost-effective synchronization of audio and video in a single integrated package that conserves board space and simplifies channel configuration.
Audio/video (A/V) synchronization issues arise because video processing is more intensive than audio processing. As a result, audio is ready for playback before the video. Without synchronization, what viewers hear will not match what they see on the screen -- where the timing of lips moving is off from the words being heard, for example -- significantly impacting the overall viewing experience. Also known as "lip sync," A/V synchronization is maintained by delaying playback of the audio stream, until the video stream has finished processing. The actual delay required for synchronization depends upon the type of A/V signals and the current video mode.
Synchronization also plays a role in wireless multi-channel speaker applications. Given the inherent processing delays of wireless transmission, it takes more time for transmitted channels than non-transmitted channels to output audio. The non-transmitted channels, therefore, must have additional delay to synchronize them with the transmitted channels.
"As TV applications are getting more sophisticated and more wireless
components are being adopted, there is a real need in the market for lip
sync devices that can be easily implemented and meet the needs of manufacturers,"
says Kevin Belnap, marketing manager for Home Audio, Texas Instruments.
"The TPA5050 digital audio delay is practically a drop-in device that
provides lip sync delay in the most cost-effective and compact manner."
analogZONE Says...
At last! Lip sync has been a problem with digital TV since the standards -- even for the DVD -- were put together mostly by digital engineers who never sought to link the video and audio together with some kind of marker that could always be used to keep the two synchronized. A programmable digital audio delay is absolutely timed right because of the release of version 1.3 of the High-Definition Multimedia Interface (HDMI) http://www.hdmi.org/resourcecenter/index.asp which allows for lip sync control. Interfacing the standard -- which, with over 400 adopters in the consumer equipment world, has become the de facto standard for the future interconnection of household entertainment products -- with the I2C interface on the TPA5050 should be a cakewalk.
The TPA5050 uses an input buffer, taking the audio data and system clocks from the digital baseband processor and feeds the data into a memory system where the amount of memory delay -- with a one bit resolution -- can be controlled from the I2C interface. At 48 kHz the system offers delays of up to 170 ms/channel for a serial stream although all the industry standard 16 - 24 bit formats are supported. TI says that if more delay in required multiple parts can be connected in series, although there is no explanation in the data sheet of how clocks would be handled in that scenario and how the two I2C interfaces would be addressed.
The nominal supply rail is 3.3 V and the supply current varies with the sampling frequency of the standard being used, ranging from about 2 mA at 48 kHz up to just over 4 mA at 192 kHz. The I/O is 5-V tolerant. Memory is cleared on power-up or after the delay is changed and no external components are required.
A simple solution to a painful problem freeing the display designer to incorporate whatever processing, particularly video motion processing, deemed necesary without having to worry about what the resulting lip sync effects will be. This will be especially true when processing is done on the fly. I wish I could retroactively fit my Sony DVD player with such a system… The TPA5050 will do extremely well, and deservedly so.
The TPA 5050 is in QFN-16 and is priced at $3.20 in 1000-piece lots.