The present disclosure relates to a method (400) for determining a clock frequency offset between a first device having a first clock and at least one second device having at least one second clock, the method comprising: receiving (401), by the at least one second device, at least one first message from the first device, wherein information regarding a time of departure of the at least one first message is in the at least one first message; determining (402), by the at least one second device, a time of arrival of the at least one first message; receiving (403), by the at least one second device, at least one second message from the first device, wherein information regarding a time of departure of the at least one second message is in the at least one second message; determining (404), by the at least one second device, a time of arrival of the at least one second message; and determining (405) a clock frequency offset between the first clock and the at least one second clock based on the time of departure of the at least one first message, the time of arrival of the at least one first message, the time of departure of the at least one second message, and the time of arrival of the at least one second message.

The disclosure further relates to a corresponding apparatus, system, computer program product and a computer readable storage medium.

In certain aspects, the present disclosure is related to devices, methods, systems and/or computer-readable media for use in an isochronous media network in which media devices connected to a network employ one or more synchronization signal to regulate or facilitate the transmission of media signals through the network. In certain aspects, the present disclosure is also related to devices, methods, systems and/or computer-readable media for use in a larger unified, or substantially unified, isochronous network created from aggregating local isochronous media networks in which media devices connected to a network employ a one or more synchronisation signal distributed from a local master clock to regulate or facilitate the transmission of media signals.

The present technology relates to a data processing apparatus and a data processing method that enable correct clock synchronization by use of clock information. The data processing apparatus receives a digital broadcast signal so as to process content included in the digital broadcast signal and clock information also included therein for use in presentation synchronization on the content and sends via a transmission path the processed content and clock information to another data processing apparatus that presents the received content. On the other hand, the another data processing apparatus receives via the transmission path the content and clock information sent from the data processing apparatus so as to process presentation synchronization on the received content on the basis of the received clock information. The present technology is applicable to data processing apparatuses configured to process content, for example.

A communication system and a communication method for one-way transmission are provided. The communication method includes: receiving, by a precision time protocol switch, a first synchronization message from a grandmaster clock; generating, by the precision time protocol switch, a second synchronization message according to the first synchronization message; transmitting, by the precision time protocol switch, the second synchronization message to a transmitting server and a programmable logic device; generating, by the transmitting server, a timestamp according to the second synchronization message; transmitting, by the transmitting server, at least one data packet and the timestamp to the precision time protocol switch; forwarding, by the precision time protocol switch, the at least one data packet and the timestamp to the programmable logic device; and determining, by the programmable logic device, whether to output the at least one data packet according to the timestamp and the second synchronization message.

A network device includes one or more ports coupled to a network, and a time synchronization module. The time synchronization module processes (i) respective path information, and (ii) respective time synchronization information included in each of at least some of a plurality of time synchronization packets received from a master clock device over two or more different communication paths and via at least one of the one or more ports, wherein the respective path information indicates a respective communication path in the network via which the respective time synchronization packet was received. The time synchronization module determines a system time clock responsive to the processing of the path information and the time synchronization information included in the at least some of the plurality of time synchronization packets.

A timestamp unit and a communication control unit for a user station. The timestamp unit includes a memory, which cyclically stores a timestamp of a message, which is transmitted via a communication network, an address counter, which is incrementable with each storing of a timestamp of a message, so that the value of the address counter corresponds to an address at which the timestamp is stored in the memory, a first interface to a host control unit via which the timestamp of a message is capturable, and a second interface to a communication control unit, which creates or reads at least one message for/from the user station, the interface including a connection for receiving a trigger signal from the communication control unit, which prompts the capturing of a timestamp, and a connection for transmitting a signal to the communication control unit, which includes the value of the address counter.

Systems and methods of this disclosure can operate to synchronize timing between communication devices and can include a timing server. The timing server can provide a communications interface for the exchange of timing messages to a first communication device. Using existing protocol messages defined in the M-CMTS architecture, additional communication devices can intercept, snoop, and extract timing information from messages between the first communication device and the timing server to adjust their internal clocks to maintain timing synchronization thereby reducing the number of communication interfaces required from a timing server.

A method is provided for synchronizing clocks on a plurality of audio playback devices. The method includes receiving a broadcast/multicast acknowledgement packet from a synchronization agent at a first audio playback device of the plurality of audio playback devices. A first timestamp representing a time when the acknowledgement packet was received by the first audio playback device is recorded. A broadcast/multicast timestamp packet is received from a time server at the first audio playback device. The timestamp packet includes a second timestamp representing a time when the time server received the acknowledgement packet from the synchronization agent. A local clock time on the first audio playback device is updated based on the first timestamp and the second timestamp. The method enables clock synchronization among the plurality of audio playback devices for synchronized playback of streamed audio via the plurality of audio playback devices.

A method and system for the post-adjustment (i.e., offline) of event timestamps to implement virtual time synchronization amongst detection node clocks. In existing methodologies with the goal of clock synchronization, clocks (and timestamps generated therefrom) are disciplined or adjusted at the recordation time of the events on a detection node (e.g., a switch/router, an Internet-of-Things (IoT) device, a wireless sensor, etc.). However, there is no particular reason for these clocks or timestamps to be accurate during the recordation time, but rather, should be accurate at their use or interpretation time. Further, through these recordation time adjustments, clock drifts and timing errors may be gradually introduced, leading to runaway inaccuracies. The disclosed method and system intentionally avoids the disciplining of clocks at event recordation times on the detection node and, instead, adjusts timestamps during interpretation times, to overcome the aforementioned issues.

A method for signaling a time and/or clock through a header station generating a transport datastream from video and/or audio data to at least one receiver of the transport datastream calculates the time information (PCR.sub.N+1; RTP.sub.N+1; T.sub.N+1) integrated in a transport data packet of the transport datastream iteratively from the time information (PCR.sub.N; RTP.sub.N; T.sub.1) of the transport data packet last transmitted in the transport datastream with integrated time information, from a transmission time of data bits transmitted since the last transmitted transport data packet with integrated time information in the transport datastream and from a clock (f.sub.PCR; f.sub.Sys). The time information (PCR.sub.N+1, PCR.sub.N; RTP.sub.N+1, RTP.sub.N; T.sub.N+1, T.sub.1) serves in each case for the signaling of times or a clock, and, in each case, contains a pulse number counted up to the transmission time of the respective transport data packet of the clock (f.sub.PCR; f.sub.Sys).