System and method for synchronizing audio-visual devices on a power line communications (PLC) network
First Claim
1. An apparatus for synchronizing video and audio streams being communicated over a power line communications (PLC) network, comprising:
- a first streaming media device configured for connecting to a power line for the receipt of operating power;
a power line communications circuit, within said first streaming media device, configured for communicating data over said power line operating as a PLC network, between said first streaming media device and at least a second streaming media device coupled to said power line; and
means for isochronously communicating a reference clock from said first streaming device over said PLC network to additional streaming devices for maintaining synchronization of device output.
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Abstract
A method and apparatus for synchronizing streaming media devices within a PLC network. Output synchronization errors exceeding ˜30 ms become noticeable when multiple streaming media devices are outputting an audio stream. The present invention provides a system and method for isochronously sending periodic reference clocks from a master device to client devices coupled to the PLC network. The client devices set their clocks based on the reference clock. In addition the clients adjust their system clock time base in response to the average divergence of the system clock with the reference clock, or a count of the number of clocks between beacon frames. In this way the client clock is adjusted to closely track the server clock so that synchronization is maintained between each of the devices. Streaming audio shared between servers and client devices is thus output across the network with high fidelity due to the accurate synchronization.
56 Citations
20 Claims
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1. An apparatus for synchronizing video and audio streams being communicated over a power line communications (PLC) network, comprising:
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a first streaming media device configured for connecting to a power line for the receipt of operating power;
a power line communications circuit, within said first streaming media device, configured for communicating data over said power line operating as a PLC network, between said first streaming media device and at least a second streaming media device coupled to said power line; and
means for isochronously communicating a reference clock from said first streaming device over said PLC network to additional streaming devices for maintaining synchronization of device output. - View Dependent Claims (2)
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3. An apparatus for synchronizing video and audio streams being communicated over a power line communications (PLC) network, comprising:
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a first streaming media device configured for connecting to a power line for the receipt of operating power;
a power line communications circuit, within said first streaming media device, configured for communicating video and audio data over said power line operating as a PLC network, between said first streaming media device and at least a second streaming media device coupled to said power line;
means for generating a beacon signal, for communicating boundaries of a beacon frame having a contention-free portion for isochronous transmissions and a non-contention-free portion for asynchronous transmissions, to devices coupled to the PLC network; and
means for outputting a reference clock within said contention-free portion of said beacon frame for updating the system time clock on media devices coupled to the PLC network to maintain synchronization. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of synchronizing the audio-video output from devices coupled to a power line communications (PLC) network, comprising:
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generating a beacon framing signal on the PLC network;
communicating streaming media including audio, video, or a combination of audio and video between devices coupled to said PLC network;
reserving a portion of each beacon frame, bounded by said beacon framing signal, for use in communicating isochronous transmissions, said portion being referred to as a contention-free portion;
reserving a time slot within said contention-free period for communicating a reference time clock; and
generating a reference time clock signal within said reserved time slot to update the system time clock on devices coupled to the PLC network for maintaining synchronization of the streaming media being output. - View Dependent Claims (17, 18, 19, 20)
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Specification