Hybrid timing scheme for transmission of packetized audio and power over a common wire

Abstract

A distributed amplification and packetized audio transmission system for clock synchronization and alignment between an audio source / power supply and endpoints with dedicated amplifiers and speakers. Ethernet audio signals are combined with power line communication (PLC) signals for transmission from the source to the endpoints over common wires. A single master clock in the source synchronizes the Ethernet audio transmitter with the PLC transmitter. Each endpoint has a PLC receiver to recover the master clock for use by its Ethernet audio receiver to provide reliable clock synchronization between the source clock and the endpoint clock. The endpoint can adjust and re-mark PTP packetized clocks according to symbol and timing information from the PLC receiver.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to European Patent Application No. 20201279.5, filed October 12, 2020, and U.S. Provisional Application No. 63 / 090,397, filed October 12, 2020, all of which are incorporated herein by reference in their entirety. Technical Field

[0003] The embodiments relate to audio systems, and more specifically to clock synchronization for transmitting digital audio and power over a common wire. Background Technology

[0004] Transmitting digital audio data over Ethernet has long been a topic of discussion and development in the audio industry. Currently, the most common method is defined in the AES 67 standard, which defines interoperability between Internet Protocol (IP) Audio and Audio over Ethernet (AoE). This method provides a mechanism for transmitting audio sample streams and audio timing to recover, decode, and time-align samples at the audio endpoint. To establish a reliable technique for synchronizing audio clocks over Ethernet, AES 67 uses the IEEE 1588 standard for Precision Time Protocol (PTP) packets. This technique is a packetized clock format where endpoints (slave devices) can receive specific PTP packets and ultimately synchronize with the master clock originating from the transmitter. The AES 67 standard and similar methods rely on Ethernet packets to transmit and receive timing information so that endpoints (slave devices) can synchronize with the master clock.

[0005] With the development of AoE, power line communication (PLC) technology has also made significant progress over the past decade, now reliably demonstrating 1 Gigabit data transmission performance over standard AC mains power line infrastructure. The basic approach used by PLC devices is to transmit digital data using multiple frequencies located at locations far above the baseband power transmission spectrum. Therefore, two transmission paths, one power path and one digital data path, can coexist on the same power line or speaker cable infrastructure. PLC technology relies on digital communication practices such as Orthogonal Frequency Division Multiplexing (OFDM) and Bipolar Phase Shift Keying (BPSK) to transmit digital data over a basic two-conductor power line. These technologies fundamentally require synchronization between the master transmitter and the downstream endpoint (slave device). Therefore, current PLC standards (e.g., Homeplug AV2, ITU-T, G.Hn, and IEEE 1901-2010) require robust mechanisms to establish clock synchronization between transmitting and receiving nodes residing on the power line bus.

[0006] Generally, the AES67 method performs poorly when dealing with delayed or jittered Ethernet packets, especially when transmitting such packets through PLC devices. Therefore, systems using packet-based clock synchronization schemes (such as AES67) are unreliable when transmitting and receiving through PLC infrastructures. Summary of the Invention

[0007] The embodiment includes a distributed amplification and packetized audio transmission system for clock synchronization and alignment between an audio source / power supply and multiple endpoints with dedicated amplifiers and speakers. Ethernet audio signals are combined with power line communication (PLC) signals and transmitted from the source to the endpoints via a common conductor. A single master clock in the source synchronizes the Ethernet audio transmitter with the PLC transmitter. Each endpoint has a PLC receiver to recover the master clock for use by its Ethernet audio receiver, providing reliable clock synchronization between the source and endpoint clocks. The transmitted PLC signals may include Precision Time Protocol (PTP) packets, and the endpoints can adjust and retime-stamp the PTP packetized clock based on symbol and timing information from the PLC receiver.

[0008] The embodiment also includes a distributed amplifier audio speaker system having an audio source that transmits audio and power via a common conductor to multiple endpoints, each endpoint having a speaker to play back the audio. The audio source may be an Ethernet audio transmitter coupled to a power line communication (PLC) transmitter, and a master clock coupled to both the Ethernet audio transmitter and the PLC transmitter, generating a master clock signal for them. The PLC transmitter is configured to generate a PLC-encoded signal including audio to the multiple endpoints. Each endpoint includes a PLC receiver coupled to an Ethernet receiver, which is coupled to a speaker and receives the PLC-encoded signal. It recovers the master clock signal from the PLC-encoded signal, synchronizing the Ethernet receiver with the Ethernet transmitter. Attached Figure Description

[0009] In the following figures, similar reference numerals are used to refer to similar elements. Although the following figures depict various examples, one or more implementations are not limited to the examples depicted in the figures.

[0010] Figure 1 A distributed amplifier (driver group) loudspeaker system is shown, which implements one or more embodiments of a clock synchronization scheme for transmitting digital audio over baseband power lines.

[0011] Figure 2 The following are illustrations of a method for using according to some embodiments. Figure 1 The components of the distributed amplification system's control and speaker unit.

[0012] Figure 3An example spectral allocation of power and audio signals transmitted through the same wires according to some embodiments is shown.

[0013] Figure 4 It shows Figure 1 The distributed amplifier system is implemented using standard off-the-shelf components according to the example embodiment.

[0014] Figure 5 The illustration shows the addition of endpoint audio clock synchronization via power line communication (PLC) timing according to some embodiments. Figure 4 A distributed amplifier system.

[0015] Figure 6 This is a flowchart illustrating a method for providing endpoint audio clock synchronization via a PLC timing system according to some embodiments.

[0016] Figure 7 An endpoint audio clock synchronization system using Precision Time Protocol (PTP) updates is illustrated according to some embodiments.

[0017] Figure 8 This is a flowchart illustrating a method for providing endpoint audio clock synchronization via PLC PTP update according to some embodiments. Detailed Implementation

[0018] The embodiments pertain to systems and methods for clock synchronization of digital audio transmitted over baseband power lines or speaker cables in an audio playback system. Any of the described embodiments can be used alone or in any combination with each other. Although various embodiments may have been inspired by various deficiencies of current and known solutions, which may be discussed in the specification, the embodiments do not necessarily address any of these deficiencies. Different embodiments may address different deficiencies, and some deficiencies may only be partially addressed.

[0019] Distributed loudspeaker system

[0020] Over the past few years, the development of systems for transmitting packaged digital audio data via power lines and speaker cables has greatly simplified wiring, improved fidelity and performance, and reduced costs. One such development is a distributed amplification or "drive group" system, in which multi-channel digital audio data and power signals appear on speaker wiring, which is routed to each drive group located at each speaker. These drive groups can demodulate and decode the desired audio channels and recover the power signals, which are then used to drive their respective speakers. In one embodiment, this technology relies on the concept of power line communication (PLC) technology to establish a reliable digital data link between the master transmitter and downstream receiver. Audio band signals and modulation techniques are used to establish power transmission and recovery. The overall goal of this system is to create speaker amplification and drive systems where a single cable can be daisy-chained between multiple speakers, but each speaker can play unique content material.

[0021] Figure 1 A distributed amplifier speaker system is illustrated, which implements one or more embodiments of a clock synchronization scheme for transmitting digital audio and power over a common baseband power line or speaker cable. Figure 1 As shown, System 100 is a multi-channel loudspeaker system with any number N loudspeakers 110. Unlike conventional loudspeaker connections where each loudspeaker channel has an amplifier, a power supply, and a separate dedicated cable, System 100 is characterized by a single main amplifier and associated control unit 102, a cable backbone (“bus”) 106, and a power supply 104 for all N loudspeaker channels 110. To achieve this simplification of the power and signal distribution infrastructure, each loudspeaker channel is associated with a dedicated loudspeaker unit 108, referred to as a “driver pack,” which receives and recovers the power and audio signals generated by the control unit 102. The number of channels N can be any practical number specified by system requirements. For standard surround sound setups, N might be 7 or 9, while for full-space audio with tall loudspeakers (e.g., Dolby), it might be 9. In a system, N can be 16 or 24 channels or more.

[0022] The infrastructure of System 100 allows audio power and signals to be distributed to multiple speakers without using high-channel-count amplifiers and multiple point-to-point cables, thereby reducing the number of audio power amplifier channels and individual speaker cables, while still allowing each speaker to have independent drive (i.e., a separate audio signal at each speaker). In one embodiment, amplifier 104 is a power supply that can be implemented as a custom or standard audio amplifier to transmit power signals via bus 106, and control unit 102 includes an N-channel digital audio transceiver and an audio signal generator that adds digital audio signals to the same bus cable.

[0023] The digital audio transceiver of unit 102 transmits multiple digital audio streams driven by a power signal generated by audio amplifier 104. These two signal streams (power and data) are transmitted simultaneously via bus 106 and received by small electronic speaker units 108 built into (or tightly coupled to) each speaker 110. Speaker units 108 recover power, receive the digital audio streams, and drive the speakers with the selected signal. In one embodiment, bus cable 106 is a single standard two-wire speaker cable of standard wire gauge (e.g., 10-20 gauge) and can be used to send multiple channels of digital audio and appropriate power to individual speakers connected to the same two-wire cable. That is, many speakers can be daisy-chained or connected in parallel while still allowing independent audio channels (i.e., different signals and volumes) to be played on each speaker. The bus cable can be implemented as a simple two-wire speaker cable or a three-wire cable, such as an AC power line with one wire grounded, or any other similar simple wire cable. Instead of traditional speaker cables (i.e., stranded cables), solid Romex (typical AC wiring cables) cables can be used.

[0024] In one embodiment, a portion of power supply 104 can be implemented as a standard power amplifier. This can also be implemented, or alternatively, as a dedicated baseband AC or DC power supply, similar to an audio amplifier but with higher power efficiency and power throughput. For this embodiment, the system would be ideally suited for maximum power delivery, minimum power loss, and lowest cost.

[0025] Loudspeaker 110 may represent a single driver or transducer within a single housing (enclosure), or a multi-driver loudspeaker or loudspeaker array with different transducers handling different audio components (e.g., bass, midrange, treble). In one embodiment, loudspeaker unit 108 may also include additional circuitry to independently drive each loudspeaker assembly (e.g., woofer, tweeter, etc.) in a dual-amplification system. Both the control unit and each loudspeaker unit include a transceiver stage that allows bidirectional data flow between the control unit's digital audio transceiver and multiple loudspeakers residing on a bus. Thus, additional information can be propagated to or from the loudspeakers. For example, the loudspeakers may report telemetry (e.g., lower corner, temperature, etc.) and / or may send setting information to the individual loudspeakers (e.g., volume control, pan / tilt angle adjustment, etc.). In a system using dual amplification within the loudspeakers, two (or more) audio signals can be derived by sending a single audio stream to loudspeaker unit 108, where the loudspeaker unit employs signal processing to derive two (or more) audio signals from a single input stream. Control unit 102 may also send multiple streams directly to the respective amplification stages within loudspeaker unit 108.

[0026] Figure 2 The following are illustrations of a method for using according to some embodiments. Figure 1 The components of the distributed amplification system include the control and speaker units. The infrastructure of System 200 is subdivided into audio amplification processes, which physically separates the power supply from each output stage and is selected to enable it to efficiently provide AC excitation to power multiple output stages.

[0027] In one embodiment, power supply 204 includes a standard audio amplifier that powers other distributed audio output stages. By eliminating one of the biggest cost drivers in any audio amplifier design—the power supply—this helps achieve efficiency through component reuse. Audio power amplifiers are typically designed as AC-DC power supplies that feed one or more low-impedance transistorized output stages. Most audio amplifiers are designed as two- to four-channel devices, with a single power supply (AC / DC offline power supply) fanning out to power the output stages. Therefore, the power supply can be implemented as a standard audio amplifier that generates a controlled audio band AC waveform and provides regulatory compliance (e.g., NRTL, CE, FCC, safety isolation, etc.).

[0028] for Figure 2 In this embodiment, the modulated input waveform applied to the power supply audio amplifier is generated by an audio signal generator in control unit 202. Because the output of the power amplifier is used solely to distribute power to the individual output stages, there are no significant fidelity or spectral purity requirements for the power amplifier. Similar to the signal present on a typical AC power supply (120Vrms, 60Hz); the power supply audio amplifier will generate an AC waveform configured to power the downstream distributed audio output stages. This allows existing audio amplifiers to be used as power supplies for the distributed output stage array, and a single cable 206 can power multiple output stages 210. As with any parallel power distribution system, the total power consumption must be properly determined and managed so that the power amplifier and cable can adequately deliver the power required by the sum of all distributed output stages connected to the line. If more power is required, or a larger number of parallel output stages are connected to the line, the power amplifier can be bridged or connected in parallel with a similar amplifier. Example power supplies could be cinema-grade amplifiers (e.g., Crown DSi2000) delivering 800W to 4 ohms per channel or 1000W to 2 ohms per channel, or any similarly rated power amplifier.

[0029] As shown in system 200, control unit 202 generates a digital audio signal, which includes immersive audio with both channel-based and object-based audio components. For Figure 2For example, an interface couples control unit 202 to renderer (e.g., CP850) 201. This interface and processor provide signals to the audio signal generator of the excitation power supply 204. The digital audio transmitter 203 of control unit 202 outputs the digital audio signal directly to the power supply output, such that both power and the digital audio signal are carried on bus cable 206. The control unit also includes appropriate circuitry for regulating power and data to ensure they are correctly transmitted on the bus in terms of timing, amplitude, and phase.

[0030] Although embodiments have been described for immersive or adaptive audio applications, it should be noted that any suitable audio format can be used, and depending on the type of interface provided in control unit 202, the input audio can be direct digital audio, mixed audio, channel-based audio, object-based audio, etc. When providing analog audio, the system may include an integrated or separate analog-to-digital converter to provide digital audio signals to drive power supply 204 and provide digital audio input to bus cable 206. In one embodiment, control unit 202 outputs digital data, primarily coupled to the output of the power supply, and the power supply input is driven by an analog audio band-modulated signal (i.e., a sine wave, pink noise, summation audio signal, etc.). Therefore, the digital data is primarily routed / coupled to the power supply output, while the power supply input can be controlled using digital or analog techniques.

[0031] In embodiments where power supply 204 includes a standard or other type of amplifier, system 200 can be configured to create a power excitation signal into the amplifier and has lines connected to the amplifier output to inject digital data streams into speaker lines or bus cables 206. The digital data stream lines can also be used as sensing lines for the controller via A / D (analog / digital) circuitry. The controller 202 can then compare the input and output signals from the respective amplifier channels. This allows for the implementation of additional functionalities in software (or equivalent circuitry), such as gain modification adjustment (e.g., the system can adjust the input signal to compensate if the user changes the amplifier gain), distortion fault monitoring, fault monitoring for the presence of signals, automatic system configuration for changing the gain structure, and other similar functions.

[0032] In one embodiment, the bus cable 206 linking the control unit 202 to each speaker unit 208 is a single two-wire speaker cable (or a three-wire power cable or the like). Data is transmitted over the bus using the Internet Protocol (IP) protocol, but other protocols may also be used. Standard power line communication formats are used to provide sufficient bandwidth and channel separation to allow channelized audio information generated by the control unit to be transmitted to the output stage. Examples of standard power line communication protocols include IEEE 1901 (HomePlug AV 1.1) and the G.hn protocol. It should be noted that the embodiments are not limited thereto, and other standardized protocols or proprietary technologies are possible for transmitting digital audio information over power cables to deliver independent audio streams to distributed output stages.

[0033] Power signals, digital audio signals, and metadata used for audio object control and lighting control are transmitted between the control unit / amplifier and the speaker unit via the same wire and encoded in different frequency bands of the spectrum. Power and audio signals can be separated by frequency bands. For example, the power component might be downgraded to a relatively low frequency band between 0 (DC) and 20 kHz, while, for example, the digital data components used for audio and lighting control might be carried in a frequency band between 1 MHz and 100 MHz, but the embodiments are not limited to this. Figure 3 Example spectral distributions of power and audio signals transmitted through the same conductors in some embodiments are shown. The spectral distribution plot shows the relationship between the signal amplitude (y-axis) 302 and its frequency (x-axis) 304. Figure 3 As shown, the audio frequency band power signal is encoded in the range of 0 to 20 kHz, while the digital audio transmission is encoded in the range of 1.8 MHz to 86 MHz. The separation between the power signal 306 and the audio signal 308 is therefore approximately 1.5 MHz. Figure 3 An example power / audio spectrum allocation is shown, and the embodiments are not limited thereto; any other similar spectrum allocation may also be used to encode audio signals for transmission over a common wire.

[0034] Figure 4 This illustrates an implementation using standard, commercially available components, according to an example embodiment. Figure 1This is a distributed amplifier system. For system 400, audio and power signals propagate in a specific order between source 401 and endpoint 411 through certain electrical components and on a common conductor 410. The audio signal originates from audio block 402 of source 401. The audio is then packaged into an Ethernet audio format (e.g., AES67 or CobraNet) using an audio transmitter (e.g., Dolby CP850, Audio Science Hono 8.0L, or similar) 404. The packaged audio is then sent to power line communication (PLC) transmitter 406, which is coupled to the output of baseband power (e.g., Crown amplifier) ​​408. Amplifier 408 is driven by the audio signal from source 402 and processed by digital signal processor (DSP) 405. Amplifier 408 then outputs a power signal to be conducted through standard two-wire speaker wiring or other similar wires or cables 410 to endpoint electronics located at or closely coupled to speaker 420. The power signal output from amplifier 408 and the packaged audio output from PLC transmitter 406 are combined at the electrically coupled output of PLC transmitter 406 and amplifier 408.

[0035] Within endpoint 411, a power line communication (PLC) receiver 412 is coupled to inbound speaker cabling 410 and operable to demodulate and recover Ethernet packets. The recovered Ethernet packets are then passed to an Ethernet audio receiver 416, which recovers the audio stream originating from the original audio source 402. The recovered audio is then amplified using a standard or custom Class D amplifier 418 to drive the speaker transducer 420. Amplifier 418 also receives a composite signal transmitted through wire 410 as input, regulated or converted by a power factor correction (PFC) component 414.

[0036] supply Figure 4 This example implementation is provided merely to illustrate a distributed amplifier speaker system that includes, or can be modified to include, a clock synchronization process. Such an example circuit is not intended to be limiting, and other implementations, components, configurations, and signal processing sequences are possible.

[0037] As previously mentioned, existing PLC systems may have some issues regarding establishing reliable audio transmission from audio source 402 to endpoint audio receiver 416. The PLC transmission and reception processes add delays and jitter to the packetized digital information, leading to decoding errors within the endpoint. Of particular concern is the impact of random PLC delays and jitter on the packetized audio timing infrastructure, which is inherently embedded in the Ethernet audio schemes used in some Ethernet audio systems. PLC delays and jitter can adversely affect the reliable recovery and synchronization of audio timing information packetized in certain AoE streams, resulting in poor transmission of Ethernet packetized audio streams through standard PLC devices. Specifically, it has been determined that certain delays and jitter added to the packetized digital information by the PLC transmission and reception processes cause decoding errors within endpoint 411.

[0038] Therefore, embodiments include clock synchronization and alignment components or systems 422, which facilitate satisfactory transmission of Ethernet-packed audio streams via standard PLC devices and common wiring (e.g., speaker wires).

[0039] like Figure 4 As shown, the distributed amplifier audio transmission and speaker playback system includes a clock synchronization and alignment component 422 to help achieve clock synchronization and alignment for packaged audio transmission over baseband power lines or speaker cables. This component, or the processes contained therein, helps resolve problems associated with poor clock synchronization when transmitting standardized audio data packets using power line communication equipment.

[0040] Master clock synchronization method

[0041] Figure 5 The illustration shows the addition of endpoint audio clock synchronization via PLC timing according to some embodiments. Figure 4 A distributed amplifier system. System 500's method uses a hybrid combination of two communication layers (e.g., AES 67 and PLC) to provide a stable and reliable clock synchronization scheme for audio transmission over baseband power lines. System 500 includes source circuitry 401, where an audio source generates a packetized Ethernet signal to be transmitted via wire 410 to endpoint 411 for playback via speaker 420, as described above. Figure 4 As described above. In this embodiment, the clock synchronization and alignment component 422 is embodied by a clock circuit 502 for the source 401 and a clock circuit 504 for the endpoint 411.

[0042] for Figure 5In this embodiment, a single master clock 502 is used within the master transmitter, which synchronizes the Ethernet audio transmitter 404 with the PLC modulator 406. Subsequently, the downstream endpoint 411 recovers and locks to the original master clock 502 using the PLC demodulator receiver 412, and then feeds this synchronized clock to the Ethernet audio receiver 416. Therefore, this method ensures reliable clock synchronization between the master transmitter and all downstream endpoints (slave devices). Due to the inherent clock synchronization requirements of modern PLC transmissions using OFDM and BPSK signaling, the master clock provided to the PLC transmitter is recovered by the downstream PLC receiver using a phase-locked loop (PLL) method.

[0043] This timing scheme also allows for proper time alignment of the clock edges with the inbound audio samples recovered from Ethernet packets. This is achieved by using PLC telemetry information (received PLC symbol delay and jitter) to adequately adjust the timing of the recovered clock edges to align with the audio sample stream. Therefore, Figure 5 The timing mechanism accomplishes two goals. First, it provides clock recovery / synchronization between the source and endpoints (i.e., ensuring phase coherence between the audio source and endpoints); second, it aligns the clock edge timing with the audio sample stream. With these features, reliable audio transmission can be achieved using packed audio on baseband power lines and speaker cables.

[0044] Figure 6 This illustrates a timing system via a PLC according to some embodiments, such as via... Figure 5 The system provides a flowchart of a method for synchronizing audio clocks at endpoints. Process 600 begins by providing a single master clock in or via an Ethernet transmitter on the source side, 602. This master clock synchronizes the Ethernet transmitter with a PLC modulator on the source side, 604. The synchronized PLC signal is then transmitted to the endpoint side via a common connector (e.g., a speaker cable), 606. The endpoint's PLC demodulation receiver receives the PLC signal and recovers and locks to the original master clock, 608. This recovered original master clock signal is then provided to the Ethernet audio receiver in the endpoint, 610. Thus, the clock of the master Ethernet transmitter is synchronized with the Ethernet receiver of the endpoint. In a speaker system with multiple (e.g., 8 to 64) speakers, this scheme ensures reliable clock synchronization between the master transmitter and all speaker endpoints.

[0045] As mentioned above Figure 5 The PLC signal transmitted from the source to the endpoint is also used to properly time-align the clock edge with the inbound audio sample recovered from the Ethernet packet. Therefore, in process 500, the transmitted synchronization PLC signal (in...) Figure 6In step 606 of the flowchart, the transmission is also used to fully adjust the timing of the recovered clock edge to align with the audio sample stream (in Figure 6 (Alignment in step 612 of the flowchart). This is accomplished using the received PLC symbol delay and jitter (PLC telemetry data) from the received PLC signals. By monitoring the symbol-to-symbol delay, latency, and nominal jitter performance of the physical layer (i.e., the speaker cable), the PLC receiver can accurately adjust and align the audio sample framing to ensure robust recovery of the audio sample stream.

[0046] Precise Time Protocol Update Method

[0047] In another embodiment, audio clock synchronization between the source and the endpoint can be achieved via PLC Precision Time Protocol (PTP) updates. The following description of this additional embodiment will focus on its differences from the previously described embodiments. Therefore, features common to both embodiments will be omitted from the following description, and it should thus be assumed that features of the previously described embodiments are implemented in, or at least may be implemented in, the other embodiment, unless otherwise required by the following description.

[0048] In this embodiment, the endpoint Ethernet receiver adjusts and re-timestamps the PTP packet clock information based on symbol timing information known within the PLC receiver. This technique requires the endpoint PLC to have accurate timing information for its incoming symbols, similar to the previously discussed embodiments.

[0049] Figure 7 An endpoint audio clock synchronization system using PTP updates is illustrated according to some embodiments. The method of system 700 uses PTP packets 709, which are used by the IEEE 1588 standard in AES67 format. System 700 includes source circuitry 701, in which an audio source generates a packetized Ethernet signal to be transmitted via wire 710 to endpoint 711 for playback via speaker 720, as described above regarding... Figure 4 As described above. In this embodiment, source 701 transmits audio data to downstream endpoint 711 in the form of PTP packets 709. PLC receiver 712 maintains specific PTP timing data 715. Using this information, endpoint receiver 711 adjusts and re-timestamps the PTP minute clock information 709 based on the symbol timing information known within the PLC receiver. The PTP timing data includes accurate timing information for its inbound symbols. In other words, the PLC receiver is configured to monitor the timing of PLC-encoded symbols to adjust and re-timestamp the PTP data packets.

[0050] Endpoint PLC 712 measures and provides symbol delay and symbol-to-symbol jitter performance, then adjusts and / or retime-stamps each PTP packet to accommodate the PLC's time-varying delay and jitter aspects. Once the PTP packets are adjusted to accommodate the PLC's delay and jitter, endpoint Ethernet audio receiver 716 utilizes its existing PTP clock synchronization scheme to accurately synchronize the endpoint clock with the clock of the source Ethernet audio transmitter 704. In this embodiment, PLC receiver 712 monitors symbol timing parameters, which are used by subsequent retiming algorithms to correct PTP packets as needed. Similar to the embodiments described above, the PLC receiver can monitor symbol-to-symbol delay, latency, and nominal jitter performance at the physical layer (speaker cable), and can pass this time offset information to the PTP algorithm, where clock and audio frame recovery algorithms can realign with the transmitter. It should be noted that in this embodiment, the clock recovery scheme uses packet-based recovery (e.g., PTP), and then adjusts the recovered clock packets to achieve alignment and synchronization, which is the opposite of the embodiments described above that use the inherent PLC clock synchronization infrastructure for synchronization. The master clock is the primary high-frequency time base used to maintain phase consistency among all digital devices within the system. Master clocks typically operate at frequencies between 12 and 100 MHz. In audio systems, the master clock can operate at frequencies several times the audio sample frequency. For example, if the audio sampling rate is 48 kHz, the master clock could operate at 24.576 MHz (512 times the audio sampling frequency). The aforementioned PTP method can be viewed as a method for transmitting and recovering the audio sampling clock over a time-varying physical layer (such as Ethernet). When data packets pass through a traditional time-varying physical layer (such as Ethernet) (i.e., through hubs / switches / routers), the packaged data may experience varying delays. Typically, in traditional systems, the varying delays (and jitter) of the traditional power line communication (PLC) physical layer can cause the PTP system to fail to recover the audio sampling clock, thus preventing PTP transmission over the PLC physical layer from functioning correctly. To address this issue, in the PTP method disclosed herein, the PLC physical layer devices (i.e., the PLC transmitter and PLC receiver) are synchronized by a master clock, and the PLC receiver monitors the delay and jitter of incoming PLC encoded data (e.g., PLC symbols transmitted over the physical power line). The PLC receiver can then use this timing information (e.g., PLC symbol delay and jitter) to adjust the timing of PTP data packets and retime-stamp them. This ensures that PTP data packets are correctly timed without gaps or signal loss, thus enabling proper playback of the audio stream.

[0051] Figure 8 This is a flowchart illustrating a method for providing endpoint audio clock synchronization via PLC PTP update according to some embodiments. Figure 8As shown, process 800 begins with the endpoint receiving a PLC signal from the source side, 802. The endpoint PLC receiver uses its internal clock recovery and symbol timing monitoring algorithm to measure and provide symbol delay and symbol-to-symbol jitter performance, 804. Then, a downstream algorithm adjusts or re-time-stamps each PTP packet to accommodate the PLC's time-varying delay and jitter aspects, 806. This algorithm changes the PTP packet timestamp to adjust for symbol delay, as measured at the nominal physical layer, and can be executed in an Ethernet audio receiver integrated circuit or programmable logic device. Once the PTP packet is adjusted to accommodate PLC delay and jitter, the endpoint Ethernet audio receiver utilizes its existing PTP clock synchronization scheme to accurately synchronize the endpoint clock with the master (source) transmitter's clock, 808. This embodiment requires the PLC receiver in the endpoint to monitor symbol timing parameters, which will be used by subsequent re-timing algorithms to correct PTP packets as needed.

[0052] This embodiment of the PLC PTP update embodiment can be compared with... Figure 6 The master clock transmission / recovery / synchronization scheme described herein is used in combination. Therefore, the signal received by the endpoint in step 802 can be a standard audio / power signal transmitted along wire 410, such as... Figure 4 As shown, or it could be as follows Figure 5 The master clock signal is shown.

[0053] The implementation can be used to play back any suitable type of audio format, including stereo, surround sound, object-based audio, or spatial (immersive) audio content. An example of an immersive audio system and related audio format is the Dolby Atmos platform. This system incorporates a height (upper / lower) dimension and can be implemented as a 5.1, 7.1, 9.1 surround system, or similar surround sound configurations (e.g., 11.1, 13.1, 19.4, etc.). Typically, these speakers are used to produce sound designed to be emitted more or less accurately from any location within a listening environment. Immersive audio can be used in a variety of venues, including cinemas, auditoriums, homes, etc. Endpoint speakers can therefore be placed at any suitable location and distance relative to the audio source. Such speakers can also be implemented in any suitable configuration, such as single or multi-way speakers, soundbars, upright or bookcase speakers, LFE (low-frequency effect) speakers, height speakers, etc.

[0054] The embodiments can also be used in any suitable powerline (AC power) infrastructure. In home applications, direct amplification systems can achieve multi-channel audio distribution throughout the house without increasing the burden on Wi-Fi or other wireless infrastructure. Since most active speakers require a connection to AC power, reliable audio transmission can be achieved directly without additional audio signal wiring. Therefore, the embodiments of the direct amplification audio systems described herein can be used in any suitable location or application, such as cinemas, home theaters, live venues, auditoriums, industrial facilities, military installations, theme parks, etc.

[0055] While the example implementation is described with respect to certain specific components, such as the Dolby Cinema Processor CP850, it should be noted that the embodiments are not limited thereto and any similar or other suitable components may be used.

[0056] Unless the context explicitly requires otherwise, throughout the specification and claims, the words “comprising,” “including,” etc., shall be interpreted in an inclusive sense, not an exclusive or exhaustive sense. The use of singular or plural terms shall also include the plural or singular, respectively. When the word “or” is used in a list of two or more items, the word encompasses the full following interpretations: any item in the list, all items in the list, and any combination of items in the list.

[0057] While one or more implementations have been described by way of example and according to specific embodiments, it should be understood that one or more implementations are not limited thereto. This description is intended to cover various modifications and similar arrangements that will be apparent to those skilled in the art. Therefore, the scope of the appended claims should be interpreted in the broadest possible sense to cover all such modifications and similar arrangements.

[0058] Various aspects of the present invention can be understood from the following exemplary embodiments (EEE):

[0059] EEE1. A distributed amplifier audio speaker system, comprising:

[0060] An audio source that transmits audio and power to multiple endpoints via a common conductor, each endpoint having a speaker for audio playback, wherein the audio source includes an Ethernet audio transmitter coupled to a power line communication (PLC) transmitter, and a master clock coupled to both the Ethernet audio transmitter and the PLC transmitter and generating a master clock signal for both the Ethernet audio transmitter and the PLC transmitter, wherein the PLC transmitter generates PLC-encoded signals including power and audio for the multiple endpoints; and

[0061] One of the plurality of endpoints receiving the PLC encoded signal, wherein the endpoint includes a PLC receiver coupled to an Ethernet receiver coupled to a speaker, wherein the PLC receiver recovers a master clock signal from the PLC encoded signal to synchronize the Ethernet receiver with an Ethernet transmitter.

[0062] The system of EEE2.EEE 1, wherein the PLC encoded signal includes PLC telemetry information, including PLC symbol delay and jitter, and wherein the endpoints further adjust the recovered master clock signal to align with the audio sample stream of the transmitted audio.

[0063] The system of EEE3.EEE2 includes an audio band power signal encoded in a first spectral range, and an audio sample stream encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

[0064] EEE4.EEE 1 systems in which the Ethernet audio transmitter uses one of the AES67 or CobraNet Ethernet audio formats.

[0065] The system is an EEE5 or EEE4 system, in which the PLC encoded signal includes one of the Homeplug AV2, ITU-T, G.HN or IEEE1901-2010 transmission standards.

[0066] A system of any one of EEE6, EEE1 to 5, wherein each of a plurality of endpoints includes a dedicated amplifier tightly coupled to a respective speaker for reproducing at least one audio component of the transmitted audio signal.

[0067] A system of any one of EEE7, EEE1 to 6, wherein a dedicated amplifier is configured to demodulate and decode the audio channel of the transmitted audio and recover the power signal from the transmitted power to drive the corresponding loudspeaker.

[0068] In EEE8 and EEE7 systems, the audio source is coupled to the endpoint via a two-wire speaker wire.

[0069] The system of any one of EEE 9. EEE 1 to 8 further includes a control unit comprising a multi-channel digital audio transceiver and an audio signal generator coupled to a Class D amplifier to transmit audio and power to multiple endpoints, and wherein the audio includes at least one of stereo, surround sound, object-based, or immersive audio content, wherein the immersive audio content includes both object-based audio components and channel-based audio components.

[0070] EEE10. A method for timing synchronization of an audio source with multiple endpoints, each having a speaker for playback of audio content, comprising:

[0071] A single master clock is provided in the Ethernet transmitter on the audio source side;

[0072] A power line communication (PLC) modulator using an audio source synchronizes the master clock with an Ethernet transmitter;

[0073] Transmit synchronized PLC signals to one of multiple endpoints via a common connector;

[0074] Receive PLC signals in the PLC demodulation receiver at the endpoint;

[0075] Recover the master clock from the received PLC signals;

[0076] The recovered master clock signal is provided to the Ethernet audio receiver in the endpoint, synchronizing the clock of the Ethernet transmitter with that of the Ethernet receiver in the endpoint.

[0077] The method of EEE11.EEE 10, wherein the PLC signal includes PLC telemetry information, including PLC symbol delay and jitter, and wherein the method further includes: adjusting the recovered master clock at the endpoints to align with an audio sample stream transmitted from an audio source to multiple endpoints.

[0078] The method of EEE 12 and EEE 11, wherein the power includes an audio band power signal encoded in a first spectral range, and an audio sample stream is encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

[0079] The method of any one of EE10 to 12, wherein the Ethernet audio transmitter uses one of the AES67 or CobraNet Ethernet audio formats, and wherein the PLC encoded signal includes one of the Homeplug AV2, ITU-T, G.HN or IEEE1901-2010 transmission standards.

[0080] The method of any one of EEE 14, EEE 10 to 13, wherein each of the plurality of endpoints includes a dedicated amplifier tightly coupled to a respective loudspeaker for reproducing at least one audio component of a transmitted audio signal, wherein the dedicated amplifier is configured to demodulate and decode an audio channel of the transmitted audio and recover a power signal from the transmitted power to drive the respective loudspeaker.

[0081] EEE15. A distributed amplifier audio speaker system, comprising:

[0082] An audio source that transmits audio and power to multiple endpoints via a common wire, each endpoint having a speaker to play back the audio, wherein the audio source includes an Ethernet audio transmitter coupled to a power line communication (PLC) transmitter, and a master clock coupled to both the Ethernet audio transmitter and the PLC transmitter and generating a master clock signal for both the Ethernet audio transmitter and the PLC transmitter, wherein the PLC transmitter generates PLC-encoded signals including power and audio for the multiple endpoints;

[0083] Precision Time Protocol (PTP) components, which use PTP signal components to transmit PLC coded signals; and

[0084] One of the plurality of endpoints receiving the PLC encoded signal and the PTP signal component, wherein the endpoint includes a PLC receiver coupled to an Ethernet receiver coupled to a speaker, wherein the PLC receiver maintains certain PTP timing data and uses this data to adjust and retime-stamp the PTP packet clock signal received from the audio source and the PTP component to compensate for any delay or jitter in the transmitted audio signal.

[0085] In EEE16.EEE 15 systems, the endpoints further monitor symbol timing parameters in the transmitted audio signal and use one or more retiming algorithms to correct received PTP packets to achieve a minimum level of clock synchronization between the audio source and the endpoint.

[0086] Systems of any of EE17, EE15, or EE16, wherein PTP packets conform to the IEEE 1588 standard in AES 67 format.

[0087] A system of EEE18 and EEE 15, wherein each of a plurality of endpoints includes a dedicated amplifier tightly coupled to a corresponding speaker for reproducing at least one audio component of a transmitted audio signal.

[0088] A system of any one of EEE 19. EEE 15 to 18, wherein the power includes an audio band power signal encoded in a first spectral range, and an audio sample stream is encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

[0089] A system of any one of EEE20, EEE 15 to 19, wherein a dedicated amplifier is configured to demodulate and decode the audio channel of the transmitted audio and recover the power signal from the transmitted power to drive the corresponding loudspeaker.

Claims

1. A distributed audio speaker system comprising an audio source and a plurality of endpoints, each of the plurality of endpoints having a speaker configured to play back audio, an Ethernet receiver coupled to the speaker, and a power line communication PLC receiver coupled to the Ethernet receiver, wherein the audio source is configured to transmit audio and power to the plurality of endpoints via a common conductor, and wherein the audio source comprises: Power source used to generate power. A power line communication PLC transmitter coupled to the power supply output. Ethernet audio transmitter coupled to the PLC transmitter, and A master clock coupled to a PLC transmitter and an Ethernet audio transmitter, wherein the master clock is configured to generate a master clock signal for both the Ethernet audio transmitter and the PLC transmitter, wherein the PLC transmitter is configured to generate a PLC-encoded signal including audio and transmit the PLC-encoded signal through the common wire, wherein one of the plurality of endpoints is configured to receive the PLC-encoded signal and power, wherein the PLC receiver of the endpoint is configured to recover the master clock signal from the PLC-encoded signal to synchronize the Ethernet receiver of the endpoint with the Ethernet transmitter of the audio source, wherein the PLC-encoded signal includes PLC telemetry information including PLC symbol delay and jitter, and wherein the endpoint is configured to further use the telemetry information to adjust the recovered master clock signal to align with the audio sample stream of the transmitted PLC-encoded signal.

2. The system of claim 1, wherein the power comprises an audio band power signal encoded in a first spectral range, and the audio sample stream is encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

3. The system of claim 1, wherein the Ethernet audio transmitter uses either AES67 or CobraNet Ethernet audio format, and wherein the PLC encoded signal includes one of Homeplug AV2, ITU-T, G.HN, or IEEE1901-2010 transmission standards.

4. The system of claim 1, wherein each of the plurality of endpoints includes a dedicated amplifier tightly coupled to a corresponding speaker for playing back at least one audio component of the transmitted audio, and wherein the dedicated amplifier is configured to demodulate and decode the audio channel of the transmitted PLC-encoded audio and recover a power signal from the transmitted power to drive the corresponding speaker.

5. The system according to claim 1, wherein, The audio source is coupled to the endpoint via a two-wire speaker wire.

6. The system according to any one of claims 1-5 further includes a control unit comprising a multi-channel digital audio transceiver and an audio signal generator coupled to a Class D amplifier, transmitting audio and power to multiple endpoints, and wherein the audio includes at least one of stereo, surround sound, object-based, or immersive audio content, wherein the immersive audio content includes both object-based audio components and channel-based audio components.

7. A method for timing synchronization of an audio source with a plurality of endpoints, each of the plurality of endpoints having a speaker for playing back audio, an Ethernet receiver coupled to the speaker, and a power line communication PLC receiver coupled to the Ethernet receiver, wherein the audio source is configured to transmit audio and power to the plurality of endpoints via a common conductor, and wherein the audio source includes a power supply for generating power, a power line communication PLC transmitter coupled to the output of the power supply, an Ethernet audio transmitter coupled to the PLC transmitter, and a master clock coupled to the PLC transmitter and the Ethernet audio transmitter, wherein... The method includes: Power is generated by the power source. The PLC transmitter generates a PLC-encoded signal that includes audio. The master clock is used to generate master clock signals for both the Ethernet audio transmitter and the PLC transmitter. The master clock signal is used to synchronize the Ethernet transmitter with the PLC transmitter. The PLC coded signal is transmitted to one of the multiple endpoints via the common wire through the PLC transmitter. Receive PLC encoded signals through the PLC receiver at the endpoint; The master clock signal is recovered from the received signal using the PLC receiver; and The recovered master clock signal is provided to the Ethernet audio receiver of the endpoint to synchronize the Ethernet receiver of the endpoint with the Ethernet transmitter of the audio source; wherein the PLC encoded signal includes PLC telemetry information, which includes PLC symbol delay and jitter, and wherein the method further includes adjusting the recovered master clock signal in the endpoint to align with the audio sample stream transmitted by the audio source to the plurality of endpoints.

8. The method according to claim 7, wherein, The power includes an audio band power signal encoded in a first spectral range, and the audio sample stream is encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

9. The method of claim 7, wherein the Ethernet audio transmitter uses one of the AES67 or CobraNet Ethernet audio formats, and wherein the PLC encoded signal includes one of the Homeplug AV2, ITU-T, G.HN, or IEEE 1901-2010 transmission standards.

10. The method according to any one of claims 7-9, wherein each of the plurality of endpoints includes a dedicated amplifier tightly coupled to a corresponding loudspeaker for playing back at least one audio component of audio transmitted from an audio source, wherein the dedicated amplifier is configured to demodulate and decode the audio channel of the transmitted PLC-encoded audio and recover a power signal from the transmitted power to drive the corresponding loudspeaker.

11. A distributed audio loudspeaker system, comprising: Audio source Multiple endpoints, each endpoint having a speaker configured to play back audio, an Ethernet receiver coupled to the speaker, and a power line communication PLC receiver coupled to the Ethernet receiver, wherein the audio source is configured to transmit audio and power to the multiple endpoints via a common conductor, and wherein the audio source includes a power supply for generating power, a PLC transmitter coupled to the output of the power supply, an Ethernet audio transmitter coupled to the PLC transmitter, and a master clock coupled to both the PLC transmitter and the Ethernet audio transmitter, the master clock being configured to generate a master clock signal for both the Ethernet audio transmitter and the PLC transmitter, wherein the PLC transmitter is configured to generate a PLC-encoded signal including audio and transmit the PLC-encoded signal via the common conductor, wherein the audio includes Precision Time Protocol (PTP) audio packets; and One of the plurality of endpoints is configured to receive the PLC-encoded signal including the PTP audio packet, wherein the PLC receiver of the endpoint is configured to monitor the timing of the PLC-encoded symbols of the PLC-encoded signal to adjust and retime-stamp the PTP audio packet received from the audio source to compensate for any delay or jitter in the transmission of the PLC-encoded signal.

12. The system of claim 11, wherein the PLC receiver at the endpoint is configured to monitor symbol timing parameters in the transmitted PLC-encoded signal and use one or more retiming algorithms to correct received PTP audio packets to achieve a minimum level of clock synchronization between the audio source and the endpoint, and wherein, PTP audio packets conform to the IEEE 1588 standard in AES 67 format.

13. The system of claim 11, wherein each of the plurality of endpoints includes a dedicated amplifier tightly coupled to a corresponding speaker for playing back at least one audio component of the transmitted audio signal.

14. The system of claim 11, wherein the power comprises an audio band power signal encoded in a first spectral range, and the audio sample stream is encoded in a second spectral range separated from the first spectral range by a defined minimum frequency difference.

15. The system according to any one of claims 11-14, wherein a dedicated amplifier is configured to demodulate and decode the audio channel of the transmitted audio and recover a power signal from the transmitted power to drive a corresponding loudspeaker.

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