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Clock synchronization for shared media playback

  • US 9,094,564 B2
  • Filed: 05/07/2010
  • Issued: 07/28/2015
  • Est. Priority Date: 05/07/2010
  • Status: Active Grant
First Claim
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1. A method for synchronizing a relative clock of a slave computing device to a global clock of a master computing device, the method comprising:

  • receiving a network packet from the master computing device, the network packet being received after one or more other network packets, and the network packet including a network packet time stamp value indicating a system time of the global clock when the network packet was transmitted;

    determining a receipt time offset that is a difference between a receipt time of the network packet and the network packet time stamp value, the receipt time indicating a time at which the network packet is received at the slave computing device as measured by the relative clock;

    determining a prior receipt time offset that is a difference between a receipt time of a previously received network packet and a network packet timestamp value included in that previously received network packet;

    comparing the receipt time offset to the prior determined receipt time offset; and

    adjusting the system time of the relative clock toward the system time of the global clock by a relative clock correction target that is updated to match a negative value of the receipt time offset only if an absolute value of the receipt time offset is smaller than an absolute value of the prior determined receipt time offset.

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