Method and system for synchronization of digital media playback

• US 8,190,680 B2
• Filed: 06/15/2005
• Issued: 05/29/2012
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: Arlo Technologies, Inc.
• Original Assignee: NETGEAR, Inc.
• Inventors: Spilo, Michael, Daub, Jonathan
• Primary Examiner(s): Fan, Hua
• Application Number:
  US11/155,002
• Publication Number:
  US 20060002681A1
• Time in Patent Office: 2,540 Days
• Field of Search: 709203-204
• US Class Current: 709/204
• 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 among multiple digital media playback devices on a network, each digital media playback device on the network being capable of initiating a synchronized playback, the method comprising, at a first digital media playback device:

receiving a user request to synchronously playback digital media content with a second digital media playback device;

initiating a time synchronization with the second digital media playback device, said initiating including;

obtaining a time difference between an estimated internal time of the second digital media playback device and an actual internal time of the second digital media playback device;

determining if the time difference is within a predetermined range; and

if the time difference is not within the predetermined range, repeating the obtaining step and the determining step;

if the time difference is within a predetermined range, determining a particular time, accounting for one or more network inherent delays, to commence synchronized playback;

providing to the second digital media playback device a particular position point in the digital media content and the particular time; and

enabling synchronized playback of the digital media content by the second digital media playback device at the particular position point and the particular time, said playback of the digital media content being synchronized with playback of the digital media content at the first digital media playback device.

2. The method of claim 1, wherein the digital media-content comprises a live streaming media signal from a source external to the network;

and

the first digital media playback device inserts markers into the live streaming media signal.

3. The method of claim 1, wherein the obtaining a time difference step comprises the steps of:

measuring a network transmission time between the first digital media playback device and the second digital media playback device;

obtaining an internal time of the second digital media playback device;

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

transmitting to the second digital media playback device the prospective receipt-of-message time; and

obtaining a difference-at-arrival between the prospective receipt-of-message time and an internal time of the second digital media playback device.

4. The method of claim 1, wherein the predetermined range is selected by a user.

5. The method of claim 3, wherein the computing step further comprises a step of offsetting the prospective receipt-of-message time to account for the measured network transmission time.

6. The method of claim 1, wherein the predetermined range is the lesser of 10% of a network transmission time and 10 msec.

7. The method of claim 1, further comprising the steps of:

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

adjusting a priority of the synchronized playback until the particular time has been reached;

wherein adjusting the priority prevents the synchronized playback from being preempted.

8. The method of claim 1, further comprising the steps of:

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

requesting the at least one digital media playback device to pause playback;

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

requesting the at least one digital media playback device to resume playback.

9. The method of claim 7, wherein the adjusting step is performed by a user.

10. The method of claim 1, wherein the one or more network inherent delays include at least one of initialization time, network response time, transmission time between network nodes, buffer size, and transmission delays.

11. A first digital media playback device for synchronizing digital media playback among multiple digital media playback devices on a network, each digital media playback device on the network being capable of initiating a synchronized playback, the first digital media playback device comprising:

a digital media playback component playing back digital media content;

a communication component receiving a user request to synchronously playback digital media content with a second digital media playback device;

a synchronization component;

initiating a time synchronization with the second digital media playback device by accessing a timekeeper component, including;

obtaining a time difference between an estimated internal time of the second digital media playback device and an actual internal time of the second digital media playback device;

determining if the time difference is within a predetermined range; and

if the time difference is not within the predetermined range, repeating the obtaining step and the determining step;

if the time difference is within a predetermined range, determining a particular time, accounting for one or more network inherent delays, to commence synchronized playback;

a processor unit providing to the second digital media playback device through the communication component a particular position point in the digital media content and the particular time; and

whereby the second digital media playback device being enabled to commence synchronized playback with the first digital media playback device at the particular position point and the particular time.

12. The device of claim 11, wherein the one or more network inherent delays include at least one of initialization time, network response time, transmission time between network nodes, buffer size, and transmission delays.

13. A non-transitory computer-readable medium comprising logic instructions executable by a first digital media playback device for synchronizing digital media playback among multiple digital media playback devices on a network, each digital media playback device on the network being capable of initiating a synchronized playback, said logic instructions, when executed:

receive a user request to synchronously playback digital media content with a second digital media playback device;

initiate a time synchronization with the second digital media playback device, said initiate includes;

obtaining a time difference between an estimated internal time of the second digital media playback device and an actual internal time of the second digital media playback device;

determining if the time difference is within a predetermined range; and

if the time difference is not within the predetermined range, repeating the obtaining step and the determining step;

if the time difference is within a predetermined range, determining a particular time, accounting for one or more network inherent delays, to commence synchronized playback;

provide to the second digital media playback device a particular position point in the digital media content and the particular time; and

enable synchronized playback of the digital media content by the second digital media playback device at the particular position point and the particular time, said playback of the digital media content being synchronized with playback of the digital media content at the first digital media playback device.

14. The computer-readable medium of claim 13, wherein the one or more network inherent delays include at least one of initialization time, network response time, transmission time between network nodes, buffer size, and transmission delays.