Method and system for synchronization of digital media playback

• US 20060002681A1
• Filed: 06/15/2005
• Published: 01/05/2006
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: Arlo Technologies, Inc.
• Original Assignee: SkipJam Corp. (NETGEAR, Inc.)
• Inventors: Daub, Jonathan, Spilo, Michael
• Granted Patent: US 8,190,680 B2
• Time in Patent Office: Days
• US Class Current: 386/220
• 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 21/43074 of additional data with content streams on the same device, e.g. of EPG data or interactive icon with a TV program
• CPC Class Codes: H04N 21/4325 by playing back content from the storage medium reproduction of recorded television signals H04N5/76; reproduction of recorded television signals H04N9/79
• CPC Class Codes: H04N 21/43615 Interfacing a Home Network, e.g. for connecting the client to a plurality of peripherals home Audio Video Interoperability [HAVI] data switching networks H04L12/2805
• CPC Class Codes: H04N 21/8455 involving pointers to the content, e.g. pointers to the I-frames of the video stream
• CPC Class Codes: H04N 5/76 Television signal recording
• CPC Class Codes: H04N 5/765 Interface circuits between an apparatus for recording and another apparatus
• CPC Class Codes: H04N 5/775 between a recording apparatus and a television receiver
• CPC Class Codes: H04N 5/781 on disks or drums
• CPC Class Codes: H04N 5/85 on discs or drums
• CPC Class Codes: H04N 9/8042 involving data reduction

Abstract

A system and method for synchronizing digital media playback at multiple digital media playback devices interconnected on a network is provided. A digital media playback device comprising a processor, a synchronization component, a timekeeper component and a digital media source performs synchronization processes to arrange for other players to begin playback at a predetermined position and time in the digital media signal. Synchronization is accomplished by processes which approximate the arrival time of a packet containing audio and/or video digital content across the network and instruct the playback devices as to when playback is to begin, and at what point in the streaming media content signal to begin playback. One method uses a time-stamp packet on the network to synchronize all players. Other methods utilize reiterative processes to narrow approximations of packet arrival time at each playback device.

Claims

1. A method for synchronizing digital media playback comprising the steps of:

providing at least two digital media playback devices coupled to a network;

playing back at a first playback device a digital media signal;

designating at least one other playback device to begin playback of the digital media signal;

requesting from the first playback device a particular position point in the media signal, a particular time associated with the particular position point, and the rate of playback; and

synchronizing the at least one other playback device to render the digital media based on the particular position point in the media signal, the particular time, and the playback rate.

2. The method of claim 1, wherein the particular time is a time at which the particular position point in the media was played back.

3. The method of claim 1, wherein the particular time is a forecast of a time at which the particular position point in the media will be played back.

4. A method of synchronizing digital media playback comprising the steps of:

providing at least two digital media playback devices coupled to a network;

playing back at a first playback device a digital media signal;

designating at least one other playback device to begin playback of the digital media signal;

requesting one of the playback devices to serve as an initiating playback device and begin a synchronization process comprising determining a particular point in the media signal where, and particular time when, synchronization is to occur; and

synchronizing the initiating playback device and the at least one other playback device to render the digital media at the particular point in the media signal and at about the particular time.

5. The method of claim 4, wherein the digital media signal is a live streaming media signal from a source external to the network;

and

the initiating playback device inserts markers into the live streaming media signal.

6. The method of claim 4, wherein the synchronizing process comprises the steps of:

requesting a time-stamp;

receiving at the initiating playback device a time-stamp packet;

resetting a timekeeper component within the initiating playback device to match the time-stamp;

searching the network for the time-stamp packet; and

resetting a timekeeper component within the at least one other playback device to match the time stamp.

7. The method of claim 6, wherein the initiating playback device provides the time-stamp packet to the network.

8. The method of claim 6, wherein the broadcasting and requesting steps are performed by the initiating playback device;

and

wherein the searching step is performed by the at least one other playback device.

9. The method of claim 4, wherein the synchronizing process comprises the steps of:

measuring a network transmission time between the initiating playback device and the at least one other playback device;

informing the initiating playback device of the internal time-of-day of the at least one other playback device;

computing a prospective receipt-of-message time, wherein the receipt-of-message time is a prediction of the internal time-of-day at message arrival;

transmitting to the at least one other playback device the receipt-of-message time;

calculating a difference-at-arrival between the receipt-of-message time and the internal time-of-day of the at least one other playback device;

sending to the initiating playback device the calculated difference-at-arrival; and

comparing the difference-at-arrival to a predetermined value.

10. The method of claim 9, wherein the predetermined value is selected by a user.

11. The method of claim 9, wherein the computing step further comprises the step of offsetting the receipt-of-message time to account for the measured transmission time.

12. The method of claim 9, further comprising the step of:

repeating the computing, transmitting, calculating, sending and comparing steps until the difference-at-arrival is at least equal to the predetermined value.

13. The method of claim 9, wherein the predetermined value is the lesser of about 10% of the network transmission time and 10 msec.

14. The method of claim 9, further comprising the step of:

repeating the computing, transmitting, calculating, sending and comparing steps until the difference-at-arrival synchronizes the playback of media to commence at a playback device in advance of the particular time by the predetermined value.

15. The method of claim 4, further comprising the steps of:

controlling at least one playback device through a computer operating system; and

adjusting the priority of the synchronization process until the particular time has been reached;

wherein adjusting the priority prevents the synchronization process from being preempted.

16. The method of claim 4, further comprising the steps of:

controlling at least one playback device through a computer operating system;

requesting at least one playback device to pause playback;

loading a portion of the digital media signal commencing at the particular position point in the media signal into buffers in the playback device; and

requesting the playback device to resume playback.

17. The method of claim 4, wherein the synchronizing process comprises the steps of:

informing the initiating playback device of the internal time-of-day of the at least one other playback device;

comparing the initiating playback device internal time-of-day with the internal time-of-day of the at least one other playback device;

measuring a network transmission time between the initiating playback device and the at least one other playback device;

computing an estimate of a one-way transmission time;

computing a prospective receipt-of-message time, wherein the receipt-of-message time is a prediction of the internal time-of-day at message arrival;

transmitting to the at least one other playback device a message containing one of the receipt-of-message time and the initiating playback device internal time-of-day;

calculating a difference-at-arrival between the message contents and the internal time-of-day of the at least one other playback device;

sending to the initiating playback device the calculated difference-at-arrival; and

comparing the difference-at-arrival to a predetermined value.

18. The method of claim 17, wherein the transmitting step and the calculating step are performed multiple instances at known intervals.

19. A method of synchronizing digital media playback comprising the steps of:

synchronizing the timekeeper component of at least two digital media players;

determining a commencement time and a media position for playback; and

playing the media at the determined commencement time, beginning from the determined media position.

20. The method of claim 19, further comprising the step of:

adjusting the commencement time of at least one digital media player so that the player begins playing the media at one of an earlier time and a later time than the determined commencement time.

21. The method of claim 20, wherein the adjusting step is performed by a user.

22. The method of claim 19, wherein the synchronizing step includes a first player transmitting its internal time-of-day to at least a second player.

23. The method of claim 19, wherein the synchronizing step includes at least one player receiving a time-of-day time stamp.

24. A system for synchronization of digital media playback comprising:

at least two digital media playback devices;

a network interconnecting the at least two playback devices;

the playback devices comprising;

a digital media playback component;

a timekeeper component;

a synchronization component;

a communication component; and

a processor component.

25. The system of claim 24, wherein said timekeeper component is initialized to the time-of-day.

27. The system of claim 24, wherein a playback device is a source of digital media content to the network.

26. The system of clam 24, wherein the processor comprises a system controller which controls the synchronization process.