Synchronizing waveform generator

• US 5,502,499 A
• Filed: 06/07/1995
• Issued: 03/26/1996
• Est. Priority Date: 12/03/1993
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Birch, Christopher H., Nicholas, Paul D., Lawrence, Steven S., Brooks, Walter R., van Staden, Christian V.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US08/478,830
• Time in Patent Office: 293 Days
• Field of Search: 348/521, 348/523, 348/524, 348/522, 358/150
• US Class Current: 348/523
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• CPC Class Codes: H04N 21/236 Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream multiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/2385 Channel allocation H04N21/266 takes precedence; Bandwidth allocation H04N21/24 takes precedence ; allocation of channels according to the instantaneous demands of the users in time-division multiplex systems H04J3/1682; admission control, resource allocation in open networks H04L12/5692; arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896; negotiating bandwidth in wireless networks H04W28/16
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/4302 Content synchronisation processes, e.g. decoder synchronisation
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite

Abstract

A multiplex frame format for transmitting digital data in a data transmission system comprises a PACKETS portion comprising a highly error-protected region and a region having only Reed Solomon encoding as an error protection measure, the PACKETS portion including low speed data. The frame format also comprises portions for transmitting medium (AUDIO) and high speed (VIDEO) data streams following the PACKETS portion. Prior to transmission, the composed frame comprising the PACKETS, AUDIO and VIDEO portions is interleaved and the BLOCK SYNC and FRAME SYNC are added. A multiplex structure control packet word of the PACKETS portion immediately follows FRAME SYNC. Thus, the FRAME SYNC word defines where interleaving begins. A demultiplexer in concert with a microcontroller of a decoder decodes the multiplex structure control word and related PACKETS and outputs digital data streams to related output peripheral processors. The BLOCK SYNC word preferably comprises one eight bit byte and contains network signaling or other data at predetermined bit positions within the word. Moreover, the frame format is flexible and may vary in horizontal and vertical dimensions as digital service streams are varied due to service requirements or priorities. The multiplexers for forming the frame according to the present invention may be arranged in redundant (hot standby) or in multi-service arrangements synchronized by a synchronizing waveform, digitally generated to comprise a continuous 3.375 MHz portion and a single cycle frame marking signal of greater magnitude but significantly lower frequency.

Claims

1. A waveform generator for generating a synchronizing waveform comprising

a continuous periodic waveform generator means for generating a continuous periodic waveform having a frequency within the television bandwidth,

interrupting means for interrupting the generation of the continuous periodic waveform,

frame marking signal generator means, responsive to the interrupting means, for generating a frame marking signal, the frame marking signal comprising one cycle of a periodic waveform having a greater amplitude and a lower frequency than that of the continuous periodic waveform.

2. The waveform generator according to claim 1, the continuous periodic waveform signal having a frequency of 3.375 MHz.

3. The waveform generator according to claim 1, the frame marking signal generator means generating the frame marking signal at twice the amplitude of that of the continuous periodic waveform.

4. The waveform generator according to claim 1, the continuous periodic waveform having an amplitude between 0.375 and 1.0 volt, peak to peak.

5. The waveform generator according to claim 1, the frame marking signal having an amplitude between 0.75 and 2.0 volts, peak to peak.

6. The waveform generator according to claim 1, the interrupting means comprising a signal at a frame rate.

7. The waveform generator according to claim 1, the frame rate having a frequency of 50 Hz.

8. The waveform generator according to claim 1, the continuous periodic waveform generator means and the frame marking signal generating means comprising

counting means for continuously outputing a first plurality of digital addresses,

memory means, responsive to the counting means, for outputing digital data representative of analog signal levels, and

digital to analog converter means, responsive to the memory means, for outputing analog signal levels, the counting means, responsive to the interrupting means, for outputing additional digital addresses until a predetermined digital address, and, thereafter, returning to outputing the first plurality of digital addresses.

9. The waveform generator according to claim 8, the first plurality of digital addresses comprising four addresses.

10. The waveform generator according to claim 8, the counting means being further responsive to a clocking means comprising a signal having a frequency at least four times greater than that of the continuous periodic waveform.

11. The waveform generator according to claim 8, the additional digital addresses being fifty-six additional addresses.

12. The waveform generator according to claim 8, the frame marking signal generator means further generating one cycle of dampened continuous periodic waveform signal prior to generating the frame marking signal.

13. The waveform generator according to claim 12, the dampening of the continuous periodic waveform signal corresponding to a cosine squared function.

14. The waveform generator according to claim 8, fuller comprising

means for filtering and for maintaining the generated waveform within predetermined limits.

15. The waveform generator according to claim 8, being coupled to a master multiplexer, for synchronizing at least one slave multiplexer to the master multiplexer.