ERROR MONITORING OF A DOLBY DIGITAL AC-3 BIT STREAM

• US 20080004735A1
• Filed: 09/12/2007
• Published: 01/03/2008
• Est. Priority Date: 06/30/1999
• Status: Active Grant

• Current Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Michener, James
• Granted Patent: US 7,848,933 B2
• Time in Patent Office: Days
• US Class Current: 700/94
• CPC Class Codes: H04H 20/89 using three or more audio channels, e.g. triphonic or quadraphonic

Abstract

Methods and apparatus for broadcasting high quality audio “studio direct” with the same digital information employed in the studio by the video producer with AC-3 digital audio signals for broadcast to integrated receiver decoders (IRD). The methods and apparatus permit proper handling of AC-3 data by switching signals to encoders in response to detection of the encoded signals representing compression of the data. Control over individual data bits such as copyright bits is maintained by determining the bit status, comparing it to a preferred status, changing the status if it does not comply with the preferred status, and reevaluating cyclical redundancy check value in each data packet to avoid disruption in the data transmission. In addition, the system includes an uplink device which automatically checks, logs and reports errors in Dolby Digital AC-3 signals by a monitor which employs a processor, a digital audio card and an SMPTE timecode reader. As an option, an ethernet interface may be provided to permit AC-3 transmission to expedite storage and transmission of the audio data by media such as compact disks. The monitor employs a state machine that finds AC-3 packets, locks into the packets and detects discontinuities or loss of signal. The monitor then computes and checks the cyclical redundancy check value of the AC-3 packet found. In addition, the system enables the device to play AC-3 signals such as Dolby Digital out in sync with video signals, regardless of the storage media for the files. A sound card having an input for receiving house reference AES clock pulses enables the AES clock of the playback signal to be locked to the frequency of a production house master as a time code reader or an editor'"'"'s contact closure match video and audio signals playback.

Claims

1. An apparatus for automatically checking cataloging and reporting errors in an AC-3 bit stream signal comprising:

a monitor including a processor with a clock,

a computer interface for converting AES signal to computer readable language and,

a time code labeler for labeling each packet with a time stamp with said processor controlling said computer interface to read data into a buffer, sending a message to the processor'"'"'s operating system in response to a detector detecting errors in said data and sending a message in response to discrepancies with said labeling.

2. The invention as defined in claim 1 wherein said detector comprises a state processor finding AC-3 packets, locking into each packet, and detecting any discontinuity in the packets or loss of packets from a signal.

3. The invention as defined in claim 1 wherein said detector is operative checking timing of on-air faults simultaneously with on-air broadcasting of said AC-3 bit stream signal.

4. The invention as defined in claim 3 wherein said detector is operative while preparing a tape for broadcast.