Patent Description:
Multi-device media systems, as well as left/right audio device pairs utilize internal clocks when communicating. Time stamp information is exchanged by the devices within a media system so that, e.g., audio may be generated by each device within a given tolerance and/or audio-video synchronization is within a given tolerance. Ideally, the tolerance between devices is small enough to not be noticeable by a user within the established zone or space the devices are arranged within. The tolerance may be larger for mutli-room systems as a user may not be able to, e.g., perceive an audible difference between rooms as well as between two audio devices within the same room. Upon initial set up of such systems, the time necessary to synchronize a first device with a second can take on the order of seconds to tens of seconds depending on the accuracy needed, for example, it takes more time to form and synchronize a group of left/right stereo devices within a single room than the time required to form and synchronize multi-room audio system. This increased time leads to degradation of the end user's enjoyment due to increased time until media is produced by the system, as well as inhibits other potential end user features, such as seamlessly moving audio from one location to another or moving audio between pre-established groups.

Additionally, due to the lack of precision of the internal clocks in electronic media devices, the devices within a predefined group may need to be periodically resynchronized to maintain accurate data transfer and media generation within the required tolerances.

Furthermore, conventional systems also allow devices to revert to a dozed state, e.g., a power-saving state, when not actively generating audio output. Within this dozed state, conventional systems are unable to transfer the amount of data necessary to resynchronized device clocks within the system. <CIT> (D1) discloses providing Precision Timing Protocol (PTP) timing and clock synchronization for wireless multimedia devices. In one aspect, a primary wireless multimedia device comprising a timing synchronization control system is provided. The timing synchronization control system is configured to apply a PTP Best-Master-Clock (BMC) algorithm logic to select a master clock from among a system clock of the primary wireless multimedia device, one of one or more connected wireless multimedia devices, or one of one or more external nodes. If the timing synchronization control system selects the system clock of the primary wireless multimedia device, a clock signal of the system clock is provided to the connected wireless multimedia devices as the master clock. If the timing synchronization control system selects a connected wireless multimedia device or an external node as the master clock, the timing synchronization control system synchronizes the system clock with the master clock. <CIT> (D2) discloses a wireless multi-channel audio system including an audio source with a wireless transceiver configured to communicate according to a standard wireless protocol and an audio controller, which are collectively configured to establish wireless communications with multiple audio sinks via a corresponding wireless link, to assign each audio sink a corresponding audio channel, to synchronize timing with each audio sink, and to transmit audio information for each audio channel to a corresponding audio sink via a corresponding wireless link. The audio source may inquire as to supported audio parameters, such as sample rate and audio codec, and selects a commonly supported configuration. The audio source may separate audio information into queues for each audio channel for each audio sink. The audio source transmits frames with timestamps and a common start time for synchronization, and the audio sinks use this information to synchronize timing and remain virtually synchronized with each other. <CIT> (D8) generally relates to interfaces and techniques for media playback on one or more devices. In accordance with some embodiments, an electronic device includes a display, one or more processors, and memory. The electronic device receives user input and, in response to receiving the user input, displays, on the display, a multi-device interface that includes: one or more indicators associated with a plurality of available playback devices that are connected to the device and available to initiate playback of media from the device, and a media playback status of the plurality of available playback devices. <CIT> (D9) discloses, in a general aspect, a system for media playback including a first media playback device configured to receive a media stream from a media casting device over a data network, the first media playback device being a member of the media playback group and a second media playback device configured to receive the media stream, the second media playback device being a member of the media playback group. The first media playback device and the second media playback device can be collectively configured to designate one of the first media playback device and the second media playback device as a leader playback device of the media playback group. The playback device not designated as the leader playback device can be designated as a follower playback device of the media playback group. The first media playback device and the second media playback device can be further collectively configured to determine a clock offset between the leader playback device and the follower playback device. The leader playback device can be configured to receive a broadcast of the media stream over the data network; play the media stream; and provide the media stream to the follower playback device. The follower playback device can be configured to play the media stream in synchronization with the leader playback device based on the clock offset.

The present disclosure is directed to improved systems and methods for synchronizing clock devices of a media system within a network. The media system can include a plurality of devices having device clocks, where each device is capable of independently selecting a primary clock device from the plurality of devices to coordinate clock synchronization of the remaining devices, e.g., secondary devices. Each device utilizes the same algorithmic rules to select the primary clock device from among the plurality of devices after an initial exchange of data during a discovery phase. The algorithmic criteria for selection of the primary clock device can be based on random or arbitrary selection, or based on at least one devices characteristic exchanged within the data obtained during the discovery phase. Once selected it is the responsibility of the primary clock device to exit a power-saving state periodically, and coordinate a clock synchronization sequence with each secondary device until each secondary device clock is synchronized to within a predetermined threshold with the primary clock of the primary clock device. Additionally, similar criteria can be applied to the selection of a primary health device to maintain the "health" of the media system and the selection of a primary media distribution device responsible for sending, receiving, or otherwise distributing media content and data to each device.

In an example, there is provided a method for synchronizing device clocks including: discovering, over a network, a plurality of devices within a media system; determining a primary clock device of the plurality of devices, the primary clock device having a primary clock; sending a clock synchronization request from the primary clock device to a secondary device of the plurality of devices, regardless of whether media content is being rendered by any of the plurality of devices; and, initiating a clock synchronization sequence wherein the clock synchronization sequence is arranged to synchronize a secondary clock of the secondary device with the primary clock of the primary clock device.

In an aspect, each device of the plurality of devices includes at least one device characteristic is selected from: an internet protocol (IP) address, a network reliability metric, or a device power type.

In an aspect, determining the primary clock device includes: selecting the primary clock device from the plurality of devices, wherein the primary clock device has a lowest IP address of the plurality of devices; selecting the primary clock device from the plurality of devices based at least in part on the network reliability metric of each device of the plurality of devices; or selecting the primary clock device from the plurality of devices, wherein the primary clock device has a wall-powered device power type.

In an aspect, the method further includes: initiating an initial clock synchronization sequence between the primary clock device and each at least one secondary device, wherein the initial clock synchronization sequence is arranged to synchronize the secondary clock of the secondary device with the primary clock; entering, with the primary clock device and the secondary device a power saving state; and, exiting, with the primary clock device the power-saving state at a predetermined time interval; exiting, with the secondary device, the power saving state upon receipt of the clock synchronization request from the primary clock device.

In an aspect, the clock synchronization sequence is arranged to synchronize the secondary clock of the secondary device with the primary clock over a first time duration.

In an aspect, the first time duration is dynamic.

In an aspect, the method further includes: receiving, at the primary clock device, a confirmation that the secondary clock and the primary clock have entered a synchronous state.

In an aspect, the method further includes: determining, at a predefined time intervals, if the primary clock device is connected to the network.

In an aspect, if the primary clock device is not connected to the network, the method further includes: determining a new primary clock device from the plurality of devices connected to the network where each device of the plurality of devices shares a clock domain identifier.

In an example, a computer program product is provided, the computer program product stored on a computer readable medium which includes a set of non-transitory computer readable instructions for synchronizing device clocks that when executed on a processor is arranged to: discover, over a network, a plurality of devices within a media system; determine a primary clock device of the plurality of devices, the primary clock device having a primary clock; send a clock synchronization request from the primary clock device to a secondary device of the plurality of devices, regardless of whether media content is being rendered by any of the plurality of devices; and, initiate a clock synchronization sequence wherein the clock synchronization sequence is arranged to synchronize a secondary clock of the secondary device with the primary clock of the primary clock device.

In an aspect, each device of the plurality of devices includes at least one device characteristic selected from: an internet protocol (IP) address, a network reliability metric, or a device power type.

In an aspect, determining the primary clock device the set of non-transitory readable instructions are arranged to: select the primary clock device from the plurality of devices, wherein the primary clock device has a lowest IP address of the plurality of devices; select the primary clock device from the plurality of devices based at least in part on the network reliability metric of each device of the plurality of devices; or select the primary clock device from the plurality of devices, wherein the primary clock device has a wall-powered device power type.

In an aspect, the set of non-transitory readable instructions is further arranged to: initiate an initial clock synchronization sequence between the primary clock device and the secondary device, wherein the initial clock synchronization sequence is arranged to synchronize the secondary clock of the secondary device with the primary clock of the primary clock device; enter, with the primary clock device and the secondary device a power saving state; exit, with the primary clock device the power-saving state at a predetermined time interval; and, exit, with the secondary device, the power saving state upon receipt of the clock synchronization request from the primary clock device.

In an aspect, the clock synchronization sequence is arranged to synchronize the secondary clock of the secondary device with the primary clock of the primary clock device over a first time duration.

In an aspect, the set of non-transitory computer readable instructions are further arranged to: receive, at the primary clock device, a confirmation that the secondary clock and the primary clock have entered a synchronous state; and, determine, at predefined time intervals, if the primary clock device is connected to the network.

In an aspect, if the primary clock device is not connected to the network, the set of non-transitory computer readable instructions are further arranged to: determine a new primary clock device from the plurality of devices connected to the network where each device of the plurality of devices shares a clock domain identifier.

In an example, there is provided a system for synchronizing device clocks the system including: a plurality of devices connected to a network, the plurality of devices including: a primary clock device having a primary clock; and, a secondary device having a secondary clock, the secondary device arranged to receive a clock synchronization request from the primary clock device; wherein the primary clock device and the secondary device are arranged to enter a clock synchronization sequence, regardless of whether media content is being rendered by any of the plurality of devices, wherein the clock synchronization sequence is arranged to synchronize the secondary clock of the secondary device with the primary clock of the primary clock device.

In an aspect, each device of the plurality of devices includes at least one device characteristic selected from: an internet protocol (IP) address, network reliability metric, or a device power type.

In an aspect, selecting the primary clock device includes: selecting the primary clock device from the plurality of devices, wherein the primary clock device has a lowest IP address of the plurality of devices; selecting the primary clock device from the plurality of devices based at least in part on the network reliability metric of each device of the plurality of devices; or selecting the primary clock device from the plurality of devices, wherein the primary clock device has a wall-powered device power type.

In an aspect, if the primary clock device is no longer connected to the network, the system selects a new primary clock device from the plurality of devices connected to the network where each device of the plurality of devices shares a clock domain identifier.

These and other aspects of the various embodiments will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the various embodiments.

The techniques and systems described herein provide numerous benefits. For example, the proposed techniques result in a situation where the clocks of all of the devices of the media system (e.g., all media devices on a user's LAN/WLAN) are synchronized at all times (or at least are intended to be synchronized, which could take multiple iterations of the synchronization techniques described herein to achieve). Such a sustained or persistent synchronization, where the synchronization is within an acceptable tolerance (e.g., within <NUM>-<NUM> milliseconds (ms)) results in decreased media device zone/group/pair creation time and thus decreased time to media rendering (e.g., audio playback). In addition, the techniques and systems described herein enables permanent media device zone/group/pair creation, stable multiroom media in the case of device drop offs due to various issues (e.g., power loss), and other experience-enhancing features, such as seamlessly moving media from one device to another without interruption in media playback and enhanced forming of media device zones/groups/pairs via various control techniques (e.g., voice or virtual personal assistant (VPA)-based techniques, in-app based techniques, and from-device based techniques). Other benefits will be apparent in light of this disclosure. Note that in some implementations, the media system is an audio-only system (e.g., including two or more speakers) that manages synchronization for only audio data, while in other implementations the media system is a video-only system (e.g., including two or more displays) that manages synchronization for only video data, while in still other implementations the media system manages synchronization for audio and video data.

Use of the techniques and systems described herein can be detected in numerous ways. For example, use of the techniques and systems can be detected based on low time to media render for high accuracy playback between media devices that have not been previously combined in a zone/group/pair, such as for stereo-paired speakers which have not previously been paired together or for surround-sound systems that had not been previously grouped. Detection can also be based on low time to media for high accuracy playback between media devices that have not rendered audio since being power cycled. Detection can also be based on analysis of network traffic during times where media devices appear to be in a low-power (or dozed) state or not actively rendering media content, as the techniques described herein operate to synchronize devices even in such states, in at least some implementations. Detection via network traffic analysis is more robust when a system (e.g., media devices on a user's LAN/WLAN) contain three or more devices, because the periodic network traffic would be centralized to a single device - the primary clock device - which provides the reference clock for the system. Other ways of detecting use of the techniques and systems described herein will be apparent in light of this disclosure.

Turning now to the figures, <FIG> is a perspective schematic view of a space S within which a media system <NUM> is provided. Media system <NUM> includes a router <NUM> arranged to connect a plurality of devices 104A-104E to a network <NUM> within space S. Router <NUM> is intended to be a network router capable of receiving and forwarding data packets within a network or networks <NUM>. Additionally, router <NUM> includes a Dynamic Host Configuration Protocol (DHCP) server or service capable of automatically providing and assigning local internet profile (IP) addresses to each device, e.g., devices 104A-104E, within the network <NUM> or networks <NUM>. Plurality of devices 104A-104E are intended to include any device capable of sending and receiving data packets containing media data, for example, data related to audio, video, and/or image applications and can include but are not limited to: televisions, smart televisions, wearable audio devices (such as headphones, earbuds, or smart glasses), sound bars, stand-alone speakers, speaker systems, smart hubs, personal computers, portable personal computers, smart phones, and tablets. Additionally, each device of plurality of devices 104A-104E is capable of entering and exiting a power-saving state <NUM> (discussed below) and entering and exiting an operating state <NUM> (discussed below). In one example, as illustrated in <FIG> and <FIG>, device 104A is a sound bar, device 104B is a portable wireless speaker, device 104C is a smart TV, and devices 104D and 104E are left and right speakers, respectively. Note that five devices are used in <FIG> for illustrative purposes only, as the techniques described herein can be used with as few as two devices and up to an unlimited number of devices. Therefore, "plurality of devices" as used herein includes "at least two devices" or "two or more devices" or "multiple devices". Network <NUM> is intended to be a local area network (LAN) or a Wireless Local Area Network (WLAN) intended to connect, via wired connections, wireless connections, or a combination of wired or wireless connections, the plurality of devices 104A-104E to router <NUM> and/or to each other within network <NUM>. However, it should be appreciated that network or networks <NUM> are not limited to local networks, for example, networks <NUM> can include servers, other devices, and routers outside of the local network and can be connected to the internet I (as shown in <FIG>). Space S is intended to be a room or a plurality of rooms within range of the LAN or WLAN network <NUM>.

Each device of plurality of devices 104A-104E includes at least one device characteristic <NUM> (shown schematically in <FIG>). Device characteristic <NUM> can be selected from at least one of: a local IP address <NUM> (assigned by, for example, the DCHP server/service of router <NUM>), a network reliability metric <NUM>, a device power input type <NUM>, or a clock domain identifier <NUM> (discussed below). The network reliability metric <NUM> can include information related to an upload speed of a particular connection, a download speed of a particular connection, the Received Signal Strength Indicator (RSSI) corresponding to a particular connection, the connection type, operating physical rate, or packet error/loss rate. The connection type could include, e.g., whether the connection type utilizes an operating frequency of <NUM> or <NUM>, or whether the connection type uses a data cable (i.e., data cable <NUM>) to transfer data, for example, where data cable <NUM> is an Ethernet cable. In such an example situation, an ethernet-cable connection type would be preferred over a <NUM> connection type, and both of those connection types would be preferred over a <NUM> connection type, thereby establishing a connection type hierarchy. The packet loss rate and consistency of operating physical rate of the link can be used to determine scalability and/or accuracy of the synchronization (e.g., to determine how many media devices can be included in a given synchronized system). The device power input type <NUM> can include information as to whether a particular device utilizes a battery, capacitor, super capacitor, or a standard alternating current (AC) or direct current (DC) power input, e.g., from a connection to a wall outlet power source <NUM> as shown in <FIG>. Additionally, each device of plurality of devices 104A-104E can include the ability to produce sound, i.e., an audio playback <NUM>. Audio playback <NUM> may correspond to data related to music, voice, or audio associated with digital or analog media, and may be produced by a transducer or other equivalent speaker components known in the art. Note that although the plurality of devices 104A-104E are primarily described herein in the context of being audio devices or at least being capable of audio playback, the techniques also apply to synchronization for video and/or image data. Therefore, each of the plurality of devices 104A-104E could include at least one of audio playback capabilities, video playback capabilities, or image display capabilities, and the techniques described herein are not intended to be limited to cover clock synchronization for only one of audio, video, or images unless otherwise explicitly stated.

As illustrated schematically in <FIG>, network <NUM> includes plurality of devices 104A-104E connected via router <NUM>. Each device of plurality of devices 104A-104E is arranged to communicate with router <NUM> and/or arranged to communicate with each other. It should be appreciated that each device can be arranged to communicate with the other devices of plurality of device 104A-104E via router <NUM> or directly with each other using at least one communication protocol <NUM>. Communication protocol <NUM> can be selected from: WiFi (IEEE <NUM> a/b/g/n/ac/e), Bluetooth Classic, Bluetooth Low-Energy (BLE), Radio Frequency Identification (RFID), ZigBee, Z-Wave, 6LoWPAN, Thread, WiFi-ah, <NUM>, <NUM>, <NUM>, <NUM>, LTE Cat <NUM>, LTE Cat <NUM>, LTE Cat <NUM>, Near Field Communications (NFC), Simple Service Discovery Protocol (SSDP), Zero-configuration networking tools or protocols (zeroconf), or any other wired or wireless protocol capable of sending and receiving data between each device of plurality of devices 104A-104E and/or router <NUM>.

It should be appreciated that within network <NUM>, each device can send and/or receive data or information relating to each device of plurality of devices 104A-104E, for example, data or information relating to each device's device characteristics <NUM>, and store each device's device characteristics <NUM> in an internal memory of each device (discussed below and illustrated in <FIG>). It should be appreciated that this discovery phase DP can utilize a different protocol to send and/or receive device information and device characteristics <NUM> than is used to stream, send, or receive media data to generate an audio playback <NUM> (discussed below), for example, the discovery phase DP could utilize SSDP protocols or zeroconf tools to discover the devices within network <NUM> and exchange device characteristics <NUM> between each device of plurality of devices 104A-104E. During the discovery phase DP, as illustrated in <FIG>, the router <NUM> or the network server sends and receives device information via communication protocol <NUM> to update a product list PL stored in the memory of each device of the plurality of devices 104A-104E. As illustrated in <FIG>, during discovery phase DP, each device can store within memory device characteristics <NUM> of each device of plurality of devices 104A-104E. Although <FIG> only illustrates example components of device 104A, it should be appreciated that each device of plurality of devices 104A-104E contain substantially similar components.

Additionally, in one example, it is desirable to synchronize device clocks so that established left/right pairs of speakers, multi-room speaker configurations, or multi-device speaker configurations can broadcast, generate, or otherwise produce audio playback <NUM> within an acceptable tolerance such that a user listening to the audio playback <NUM> cannot distinguish between audio playback <NUM> produced by each speaker within a space S. To accomplish this synchronization, a primary device can be selected from the plurality of devices 104A-104E. As illustrated in <FIG>, in one example, the primary device is selected as a primary clock device <NUM>, e.g., a device responsible for initiating clock synchronization sequences <NUM> (discussed below) and sending and receiving clock synchronization requests <NUM> (discussed below) and acknowledgements <NUM> (discussed below) between each device of plurality of device 104A-104E. Furthermore, once a primary clock device <NUM> is selected from the plurality of devices 104A-104E, the remaining devices become secondary devices 128A-128E. For example, if device 104A is selected as the primary clock device <NUM>, the remaining devices 104B-104E become secondary devices 128B-128E.

In the foregoing example, each device 104A-104E includes an internal device clock capable of keeping independent time. This can be accomplished through various circuit components, for example, through the use of a crystal quartz resonator within each device of the plurality of devices 104A-104E. Once a primary clock device <NUM> is selected from the plurality of devices 104A-104E, the primary clock device <NUM>'s clock becomes the primary clock <NUM> for media system <NUM>. Moreover, once the primary clock device <NUM> is selected and the primary clock <NUM> has been established, each secondary device 128A-128E includes a secondary clock 132A-132E. Therefore, given the example discussed above, primary clock device <NUM> is device 104A having a primary clock <NUM>, while the remaining devices 104B-104E become secondary devices 128B-128E having secondary clocks 132B-132E, respectively.

To aid in selection of the primary clock device <NUM>, each device of plurality of devices 104A-104E within network <NUM> is arranged to store and execute, on a respective memory and processor of each device, a set of non-transitory computer readable instructions related to an algorithm for selecting the primary clock device <NUM> or a primary media distribution device <NUM> (discussed below). The algorithm, executable on each device of plurality of devices 104A-104E, can utilize the same rule or instruction set to select the primary clock device <NUM>. For example, the algorithm can be arranged to receive data relating the device characteristics <NUM> of each device of plurality of devices 104A-104E and determine or select the primary clock device <NUM> based on at least one device characteristic <NUM> of the devices of the plurality of devices 104A-104E that have been stored in the memory of each device connected within network <NUM>. In one example, the algorithm, executable on each device of plurality of devices 104A-104E, is configured to indicate that the primary clock device <NUM> should be the device with the lowest local IP address. In this way, each device of plurality of devices 104A-104E will know which device of the plurality is the primary clock device for the purpose of clock synchronization (discussed below). Alternatively, the algorithm can select the primary clock device <NUM> from the plurality of devices 104A-104E randomly or arbitrarily. Additionally, the set of non-transitory computer-readable instructions can relate to or contain instructions dedicated to separate software services, for example, each device of plurality of devices 104A-104E can have a dedicated service for power management, i.e., a power service <NUM> (shown in <FIG>), and can have a dedicated service for maintaining and synchronizing clocks, i.e., a clock synchronization service <NUM> (shown in <FIG>) as will be discussed below. In some implementations, the algorithm for selecting the primary clock device <NUM> is stored and/or executed on only one of devices 104A-104E, and the primary clock device selection information is then received by the other devices (e.g., directly from the only one of the devices making the selection or from another source). In some implementations, the algorithm for selecting the primary clock device <NUM> is stored and/or executed at a location that is separate from devices 104A-104E, such as at a controller that interfaces with one or more of devices 104A-104E and/or in the cloud (e.g., via internet connection I shown in <FIG> or via an internet connection of a connected controller, such as a smartphone or tablet).

As described above and illustrated in <FIG>, each device of plurality of device 104A-104E can enter or exit a power-saving state <NUM> throughout normal operation of media system <NUM>. The entry into or exit from power-saving state <NUM> to operation state <NUM> and vice-versa is managed by each device's power service <NUM>. For example, after ten (<NUM>) minutes without producing audio playback <NUM>, the power service <NUM> of device 104A can cause device 104A to enter power-saving state <NUM>. Within power-saving state <NUM>, device 104A can still send or receive data; however, the rate at which device 104A sends or receives data while in the power-saving state <NUM> is diminished. Additionally, all of the remaining devices of the plurality of devices similarly enter a power-saving state <NUM> after a set duration of inactivity. However, as mentioned above, even in the power-saving state <NUM> it is desirable to have the clocks of each device synchronized, or at least synchronized within a certain margin of error, such that when each device exits the power-saving state <NUM> and enters an operational state <NUM> the devices are already synchronized and can proceed directly into normal operation to, for example, produce audio playback <NUM>.

In one example, primary clock device <NUM>, once selected, has the responsibility of independently exiting power-saving state <NUM> and entering the operating state <NUM>, at a predetermined time interval <NUM>, and while in the operating state <NUM> coordinating a clock synchronization sequence <NUM> with each secondary device of the plurality of devices 104A-104E. In one non-limiting example, the predetermined time interval <NUM> is on the order of <NUM> minutes. However, it should be appreciated that this predetermined time interval can be any time interval greater than <NUM> seconds, such as every <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> minutes, to provide some additional examples. In some implementations, the predetermined time interval is not constant and changes based on one or more variables, such as information received from synchronization sequence <NUM> (e.g., how long it takes for the one or more secondary devices to become synchronized). As illustrated in <FIG>, coordination of the clock synchronization process is managed by the clock synchronization service <NUM> and can include: sending a clock synchronization request <NUM> from the primary clock device <NUM> to a secondary device 128A-128E, initiating an exit of the secondary device 128A-128E from a power saving state <NUM> if the secondary device 128A-128E is in a power-saving state <NUM> upon receipt of the clock synchronization request <NUM>, receiving an acknowledgement <NUM> from the secondary device 128A-128E that the clock synchronization request <NUM> was received by the secondary device 128A-128E, and upon receipt of the acknowledgement <NUM> by the primary clock device <NUM>, entering the clock synchronization sequence <NUM>. The clock synchronization sequence <NUM> can utilize a clock synchronization protocol <NUM> selected from: a Clock-sampling mutual network synchronization protocol (CS-MNS), a Network Time Protocol (NTP), a Precision Time Protocol (PTP), a Reference Broadcast Time Synchronization protocol (RBS), Synchronous Ethernet protocol, Data-Plane Time-Synchronization Protocol (DPTP) or any other protocol capable of sending, receiving and synchronizing two device clocks over a wired or wireless connection.

Once initiated, the clock synchronization sequence <NUM> will run for a predetermined duration of time, i.e., a first time duration <NUM>. First time duration <NUM>, can be, for example, <NUM> seconds to prevent significant power drain in the event that the primary clock device <NUM> is powered by a battery, capacitor, or super-capacitor as discussed above; however, it should be appreciated that any time interval can be selected, such as <NUM>, <NUM>, <NUM>, or <NUM> seconds, or <NUM>, <NUM>, or <NUM> minutes. After the first time duration <NUM>, the secondary device 128A-128E can run a check to determine if the primary clock <NUM> and the secondary clock <NUM> match within a predefined threshold, e.g., within a range of plus or minus <NUM> milliseconds. It should be apprecaitated that the predefined threshold can be selected based on the particular application of plurality of devices 104A-104E. In one example, the primary clock <NUM> and secondary clock <NUM> are positioned within a left/right stereo pair of audio devices. In this example, as the devices of a left/right stereo pair are typically in close proximity to each other, the predefined threshold that the device clocks must maintain is over a smaller or narrower range of plus/minus values, for example, within a range of plus or minus <NUM> microseconds, e.g., <NUM> microseconds, <NUM> microseconds, <NUM> microseconds, etc. In another example, the primary clock <NUM> and secondary clock <NUM> are a part of a multi-room system of audio devices. In this example, as the devices of multi-room system are typically not in close proximity to each other, the predefined threshold that the device clocks must maintain is over a larger or broader range of plus/minus values, for example, within a range of plus or minus <NUM> milliseconds, e.g., <NUM> millisecond, <NUM> milliseconds, <NUM> milliseconds, etc. If the two clocks are within this predefined threshold, the secondary clock sends a confirmation <NUM> to the primary clock device <NUM> that the primary clock <NUM> and the secondary clock <NUM> have entered a synchronized state <NUM>, for example, a state where the primary clock and the secondary clock <NUM> are within the predefined threshold. If the check resolves in the negative, e.g., the two clocks are not within the predefined threshold, the secondary clock sends a negative confirmation that the two clocks are not in a synchronized state <NUM> and the primary clock device <NUM> can reinitiate the clock synchronization sequence <NUM> with the secondary device 128A-128E. This process continues until the confirmation <NUM> that the two clocks are in a synchronized state <NUM> or continues for a predetermined number of cycles, e.g., three cycles, and then terminate regardless of whether the two clocks are in the synchronous state <NUM>. Additionally, it should be appreciated that first time duration <NUM> can be dynamic. In other words, if the primary and secondary clocks continuously fall into a synchronous state after <NUM> seconds of synchronization sequence <NUM>, first time duration can be limited in future synchronizations to <NUM>-<NUM> seconds to promote efficient power use. Furthermore, the primary clock device <NUM> can simultaneously or sequentially perform this synchronization process with every secondary device connected to network <NUM> and/or any device discovered during the discovery phase DP discussed above. Once each secondary device has participated in the clock synchronization process discussed above, each secondary device can optionally reenter power-saving state <NUM> or continue within the operational state <NUM>, and once all of the discovered devices connected to the network <NUM> have participated in the synchronization process, the primary clock device <NUM> can optionally reenter the power-saving state <NUM>.

Additionally, periodically it may be necessary and/or desirable to check whether the selected primary clock device <NUM> is still connected to the network <NUM>. To further the above example, where device 104A is selected as the primary clock device <NUM>, it is possible that during the operation of media system <NUM>, device 104A is disconnected from network <NUM>. This could happen as a result of, for example, device 104A running out of power in the event device 104A is battery powered, or some other form of interference with the data communication to device 104A. If a disconnection occurs, it would be desirable to promote another device from the plurality of devices 104A-104E as a new primary clock device <NUM> as each device of the plurality of devices 104A-104E is presumably operating on the same clock domain <NUM>, e.g., all running clocks that are synchronized with each other, or at least synchronized with each other within a predetermined threshold. The selection of a new primary clock device <NUM> from the plurality of devices 104B-104E in the event device 104A is disconnected from network <NUM> is illustrated in <FIG>. To aid in the selection of a new primary clock device <NUM>, each device of the plurality of devices 104B-104E utilizes a clock domain identifier <NUM> (illustrated in <FIG>), which is included in each device's device characteristics <NUM> as discussed above. As each device of plurality of devices 104A-104E within the same clock domain <NUM> already have each device's device characteristics <NUM> stored in their respective memories, the algorithm, executable independently on each device, can simply automatically select the next best device from within the clock domain <NUM> that meets the same rule or instruction set as originally used to select the primary clock device <NUM> to select the new primary clock device <NUM> from the remaining devices of the plurality of devices 104A-104E. Importantly, the process of synchronizing clocks, as discussed above, is not affected by the operational states of any of the devices or the rendering of content, i.e., media data and/or audio playback <NUM>. In other words, some or all of the devices of plurality of devices 104A-104E, prior to, during, and/or after the synchronization process discussed herein, can continue to send and receive media data, produce audio playback <NUM>, and/or otherwise render audio data regardless of and unimpeded by the synchronization process.

Given the foregoing, in addition to selecting a primary clock device, i.e., primary clock device <NUM>, it should be appreciated that media system <NUM> can utilize similar selection techniques and rules to select a primary health device <NUM> (not shown) and a primary media distribution device <NUM> (not shown). The primary health device <NUM>, once selected, is responsible for sending and receiving requests and acknowledgments from every device of the plurality of devices 104A-104E to ensure proper "health" (e.g., responsiveness and/or level of operation) of each device, for example, the primary health device periodically, i.e., at a predefined time interval <NUM> (not shown), sends request signals to check that each device established in its product list PL, obtained in the discovery phase DP discussed above, is still responsive and ensure that each device's respective device characteristics <NUM> have not changed in a way that could affect the media system's performance. If something has changed, the primary health device <NUM> can send corresponding instructions to each device of plurality of devices 104A-104E requesting that each device reenter the discovery phase DP and update their product lists PL. It should be appreciated that the algorithmic criteria for selection of the primary health device could be the same algorithmic criteria used to select primary clock device <NUM>, and therefore, the primary clock device <NUM> and the primary health device <NUM> can be embodied by the same device. In one example, the primary health device <NUM> is a separate device from the primary clock device <NUM>. In this example, the primary health device <NUM> can periodically obtain information from the devices within network <NUM>. If any of the devices fail to respond to the requests of the primary health device <NUM>, for example, if they disconnect from the network <NUM>, primary health device <NUM> is arranged to indicate to each device that they reenter the discovery phase DP and update their respective product lists PL. Importantly, the primary health device <NUM> indicates to the network <NUM> that the primary clock device <NUM> is no longer connected to the network and that a new primary clock device <NUM> should be selected as discussed above and illustrated in <FIG>.

Similarly, each device of plurality of devices 104A-104E can be designated as a primary media distribution device <NUM> through similar algorithmic criteria as is used to select the primary clock device <NUM> and the primary health device <NUM>. The primary media distribution device <NUM> is responsible for sending and receiving media data to each device within network <NUM>, e.g., data relating to music, voice, or other forms of audio data or video data such that each device can produce audio playback <NUM>. In one example, primary media distribution device <NUM> can receive an audio stream, video stream, or series of images, from, e.g., a peripheral device such as a smart phone or other media source, and then send, receive, transmit, or otherwise distribute that media data to the other devices of plurality of devices 104A-104E within network <NUM>. As the same algorithmic criteria used to select the primary clock device <NUM> can be used to select the primary health device <NUM> and the primary media distribution device <NUM>, it should be appreciated that each primary device can be embodied within a single device of plurality of devices 104A-104E. As will be discussed below, the interaction of each primary device, i.e., primary clock device <NUM>, primary health device <NUM>, and primary media distribution device <NUM>, maintains a functioning ecosystem of devices. For example, the primary clock device <NUM> will ensure each device's clocks are synchronized within a predefined threshold so that the primary media distribution device <NUM> accurately sends and receives data packets with accurate time stamps between each device so that they produce audio playback <NUM> within space S in a synchronized fashion. Additionally, the primary health device <NUM> periodically checks the devices connected to the network to at least ensure that the primary clock device <NUM> is constantly connected to the network and available to maintain clock synchronization across media system <NUM>.

In one example operation of media system <NUM>, after each device of plurality of devices 104A-104E is initially powered on within space S, each device communicates with the other devices of the plurality directly or via router <NUM> during a discovery phase DP, as illustrated schematically in <FIG>. During this discovery phase DP, each device will send and receive information relating to, for example, device characteristics <NUM> of each device connected to the network within space S. Each device, will then update a product list PL which includes information relating to all of the other devices connected within network <NUM>, and stores each device's device characteristics <NUM> in the memory of each device as shown schematically in <FIG>. As discussed above, each device can utilized an algorithm stored in memory and executable by a processor of each device, which determines, based on a set of rules or predefined instructions which device of plurality of devices 104A-104E will be selected or promoted to the role of primary clock device <NUM> (shown in <FIG>). Additionally, using the same or different algorithmic criteria, media system <NUM> can designate or select a primary health device <NUM> (not shown) and a primary media distribution device <NUM> (not shown). In one example, the algorithm dictates that the primary clock device <NUM> be selected from the device of the plurality of devices 104A-104E that has the lowest assigned local IP address <NUM> (as assigned by the DHCP server/service within router <NUM>). Alternatively or additionally, the algorithm can layer the preferences for selection of the primary clock device <NUM>, for example, as the device that has a device power type <NUM> that indicates that it is a wall powered device, i.e., is connected to wall outlet <NUM> (shown in <FIG>) and has the lowest IP address <NUM> of the devices that are wall outlet powered. Once the primary clock device <NUM> is selected, e.g., device 104A, an initial clock synchronization sequence ICS (not shown) is initiated. This sequence can take longer than the periodic synchronization cycles discussed herein in order to place each device on the same clock domain <NUM>, e.g., have every clock synchronized to within a predetermined threshold. Each device can enter or exit a power-saving state <NUM> as needed within network <NUM>; however, it is the responsibility of the primary clock device <NUM> to periodically exit power-saving state <NUM>, if it was in power-saving state <NUM>, at predetermined time interval <NUM>. After the primaFry clock device <NUM>, i.e., device 104A, exits power-saving state <NUM>, device 104A begins a synchronization process with each secondary device 128B-128E, which correspond to devices 104B-104E of plurality of devices 104A-104E. The synchronization process involves sending a clock synchronization request <NUM> from the primary clock device <NUM> to each secondary device 128B-128E, and receiving an acknowledgment <NUM> from each of the secondary devices 128B-<NUM>. After each device exits the power-saving state <NUM> in response to the clock synchronization request <NUM>, each secondary device 128B-128E enters a clock synchronization sequence <NUM> with the primary clock device <NUM> until the secondary clocks 132B-132E are in a synchronous state <NUM> (not shown) with the primary clock <NUM> of primary clock device <NUM>. Once in the synchronous state <NUM> (not shown), each device can optionally resume the state it was in prior to the clock synchronization process, for example, each device can optionally reenter power-saving mode <NUM> or may continue the production of audio playback <NUM> in the operational state <NUM>.

Once each device of plurality of secondary devices 128B-128E is synchronized within the predetermined threshold, each secondary clock <NUM> of each secondary device 128B-128E as well as primary clock <NUM> of primary clock device <NUM> are now on the same clock domain <NUM>. In the event that the primary media distribution device <NUM> and the primary clock device <NUM> are not the same device, for example, where the primary media distribution device <NUM> is selected from the plurality of secondary devices 128B-128E, any locally acquired media data to be distributed from the primary media distribution device <NUM> to and among the plurality of devices 140A-104E will have local timestamp data <NUM> which will need to be converted to the synchronized timestamp data <NUM> of the clock domain <NUM> by the primary media distribution device <NUM>. Additionally, every secondary device 128B-128E when receiving locally acquired media data having local time stamp data <NUM>, can make adjustments to any local timestamp data <NUM> so that it conforms with the timestamp data of the clock domain <NUM>, i.e., the synchronized timestamp data <NUM>. Local timestamp data <NUM> can include packet timestamps <NUM> for each packet of data sent corresponding to media data sent and/or received by the primary media distribution device <NUM> as well as any time-offset required to convert the local timestamp data <NUM> to the synchronized timestamp data <NUM> for use among the devices within the clock domain <NUM>.

<FIG> include a flowchart illustrating the steps of method <NUM> as described herein. Method <NUM> includes, for example: discovering, over a network <NUM>, a plurality of devices 104A-104E within a media system <NUM> (step <NUM>); determining a primary clock device <NUM> of the plurality of devices 104A-104E, the primary clock device <NUM> having a primary clock <NUM> (step <NUM>); selecting the primary clock device <NUM> from the plurality of devices 104A-104E, wherein the primary clock device <NUM> has a lowest IP address <NUM> of the plurality of devices 104A-104E (step 204A); selecting the primary clock device <NUM> from the plurality of devices 104A-104E based at least in part on the network reliability metric <NUM> of each device of the plurality of devices 104A-104E (step 204B); or selecting the primary clock device <NUM> from the plurality of devices 104A-104E, wherein the primary clock device <NUM> has a wall-powered device power type <NUM> (step 204C). Method <NUM> can further include, for example: initiating an initial clock synchronization sequence ICS between the primary clock device <NUM> and each at least one secondary device <NUM>, wherein the initial clock synchronization sequence ICS is arranged to synchronize the secondary clock <NUM> of the secondary device <NUM> with the primary clock <NUM> (step <NUM>); entering, with the primary clock device <NUM> and the secondary device <NUM> a power-saving state <NUM> (step <NUM>); exiting, with the primary clock device <NUM> the power-saving state <NUM> at a predetermined time interval <NUM> (step <NUM>); sending a clock synchronization request <NUM> from the primary clock device <NUM> to a secondary device <NUM> of the plurality of devices 104A-104E, regardless of whether media content is being rendered by any of the plurality of devices 104A-104E (step <NUM>); exiting, with the secondary device <NUM>, the power-saving state <NUM> upon receipt of the clock synchronization request <NUM> from the primary clock device <NUM> (step <NUM>); initiating a clock synchronization sequence <NUM> wherein the clock synchronization sequence <NUM> is arranged to synchronize a secondary clock <NUM> of the secondary device <NUM> with the primary clock <NUM> of the primary clock device <NUM> (step <NUM>); and receiving, at the primary clock device <NUM>, a confirmation <NUM> that the secondary clock <NUM> and the primary clock <NUM> have entered a synchronous state <NUM> (not shown)(step <NUM>). Once synchronized, method <NUM> can also include: determining, at predefined time intervals <NUM>, if the primary clock device is connected to the network using, for example, a primary health device <NUM> (step <NUM>); and determining a new primary clock device <NUM> from the plurality of devices 104A-104E connected to the network <NUM> where each device of the plurality of devices 104A-104E shares a clock domain identifier <NUM> if the primary clock device <NUM> is no longer connected to the network <NUM> (step <NUM>).

The above-described examples of the described subject matter can be implemented in any of numerous ways. For example, some aspects may be implemented using hardware, software or a combination thereof. When any aspect is implemented at least in part in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single device or computer or distributed among multiple devices/computers.

The present disclosure may be implemented as a system, a method, and/or a computer program product at any possible technical detail level of integration.

A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having iiistnictions recorded thereon, and any suitable combination of the foregoing.

Computer readable program instructions for carrying out operations of the present disclosure may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, statesetting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the "C" programming language or similar programming languages. In some examples, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure.

Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to examples of the disclosure.

The computer readable program instructions may be provided to a processor of a, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various examples of the present disclosure.

Other implementations are within the scope of the following claims and other claims to which the applicant may be entitled.

While various examples have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the examples described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific examples described herein. It is, therefore, to be understood that the foregoing examples are presented by way of example only and that, within the scope of the appended claims.

Claim 1:
A method (<NUM>) for synchronizing device clocks comprising:
discovering (<NUM>), over a network, a plurality of devices (<NUM>) within a media system;
each device of the plurality of devices selecting (<NUM>) a primary clock device (<NUM>) of the plurality of devices, by utilizing the same algorithmic rules, the primary clock device having a primary clock (<NUM>);
sending (<NUM>) a clock synchronization request (<NUM>) from the primary clock device to a secondary device (<NUM>) of the plurality of devices, regardless of whether media content is being rendered by any of the plurality of devices; and,
then initiating (<NUM>;<NUM>) a clock synchronization sequence (<NUM>) wherein the clock synchronization sequence is arranged to synchronize a secondary clock of the secondary device with the primary clock of the primary clock device.