Synchronization method and decoder

• US 6,313,879 B1
• Filed: 09/11/1998
• Issued: 11/06/2001
• Est. Priority Date: 10/09/1997
• Status: Expired due to Term

• Current Assignee: Lenovo PC International Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Asamoto, Noriaki, Kubo, Hiroaki
• Primary Examiner(s): Lee, Michael
• Assistant Examiner(s): DESIR, JEAN WICEL
• Application Number:
  US09/151,572
• Time in Patent Office: 1,152 Days
• Field of Search: H04/N.506, H04/N.5073, 348/518, 348/500, 348/512, 348/515, 348/516, 348/524, 348/537, 348/423.1, 348/425.4, 375/293, 375/294, 375/327, 375/376, 375/240.28, 375/373, 375/364, 375/365, 375/366, 386/71, 386/84, 386/119
• US Class Current: 348/512
• 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

Abstract

When short MPEG2 data transfer streams, such as those used for commercials, are sequentially distributed within a short period of time, a decoder method synchronizes the transfer and prevents accumulation of data in a buffer and data losses. The synchronization method extracts sync data originating at the transmission source from a received data stream; acquires sync data for a decoder based on a reference clock; compares the sync data originating at the transmission source with the sync data for the decoder in order to sequentially obtain control values, sequentially updates the frequency of the reference clock for transfer synchronization for the received data stream; determines whether or not a data stream that differs from the received data stream has been received; and employs, when a different data stream has been received, the reference clock obtained when the received data stream has been received, to initiate transfer synchronization for the different data stream.

Claims

1. A decoder comprising a feedback circuit including a comparator, a control value determination means, an oscillator and a counter for decoding an encoded data stream that is distributed across a network and that includes sync data originating at a transmission source, said decoder comprising:

an extraction circuit for extracting from a received data stream said sync data originating at said transmission source;

an oscillator for generating a reference clock used to decode data and for varying the frequency of said reference clock in accordance with a control value;

a counter for receiving said reference clock produced by said oscillator and for setting sync data for said decoder in accordance with said reference clock;

a comparator for acquiring a difference between said sync data originating at said transmission source and said sync data at said decoder;

control value determination means provided between said comparator and said oscillator for determining said control value in accordance with said acquired difference; and

determination means for permitting, when said difference between said sync data originating at said transmission source and said sync data at said decoder is greater than a predetermined limit value, said control value determination means to employ as an initial value, the frequency of the reference clock that is currently locked to initiate new transfer synchronization.

2. The decoder according to claim 1, wherein said data stream is an MPEG compatible data stream.