Digital Audio Time Code

Sigma Electronics

Sigma DATC Digital Audio Time Code

Anew document explaining DATC and its uses is available as of November20, 2003. To view a PDF version of this document, clickhere. SigmaElectronics is also now giving demonstrations of our DATC technology. Toschedule a demonstration of DATC or any of our products, please call ustoll free at (866)223-7253 in the USA or +1 (717) 569-2681 outside theUSA, or email us at: sales@a2dsolutions.com.
What is DATC? DATC stands for Digital Audio Time Code. It is a method of insertingaccurate signal timing information within the user bits of an AESdigital audio signal. It is formatted: HH:MM:SS:BBB orHours:Minutes:Seconds:Blocks, where Blocks are AES data blocks (192samples). DATC can only be utilized for AES signals offixed sample rates at 48kHz, 96kHz and 192kHz, which result in blockcounts per second of 0-249, 0-499 and 0-999 respectively. WhyDATC? DATC has been conceived to provide an accurate method of comparing theorigination time of video and audio signals so that individual pathdelays can be calculated and corrected. Without DATC, if video andaudio signal coincidence is lost, there is no simple way to providerecovery. In the past, audio delays of fixed length have been used tocompensate for identifiable video path delays. Today, path delays have become longer and insome cases dynamically variable, making accurate delay compensationpractically impossible using traditional methods. With DATC it is nowpossible to extract timing data from video and audio signals and makecomparisons to accurately determine each signals relative position. DATCand Compression Most methods for compressing audio retain AES user bit data; mezzaninetransport schemes such as Dolby E and APT pass these bits withoutinterference. Therefore extracting DATC from compressed audio can bereliably performed. On the other hand, some video compression schemesdo not carry SMPTE time code data, but instead may recode it as a timestamp within the compressed data. Naturally, this time stamping must berecovered and converted back to SMPTE time code format in order forcomparison to be made.
DATC Products There are two initial DATC products from Sigma Electronics; An AESreference generator that can read SMPTE time code and generate DATC andan AES delay compensator that can be used to insert as well as compareDATC data to adjust delay times. These products are designed tofunction together, via our OctaBus interface, for DATC insertion orcomparison and automatic delay compensation. Toview these products, click here