Hybrid clocking scheme for transmitting packetized audio and power over a common conductor

Abstract

A distributed amplification and packetized audio transmission system that uses dedicated amplifiers and speakers for clock synchronization and alignment between audio / power and endpoints. Ethernet audio signals are combined with power line communication (PLC) signals for transmission over a common conductor from the source to the endpoints. A single master clock at the source synchronizes the Ethernet audio transmitter with the PLC transmitter. Each endpoint has a PLC receiver that recovers the master clock for use in its Ethernet audio receiver to provide reliable clock synchronization between the source clock and the endpoint clock. The endpoints may re-timestamp their PTP packetized clocks based on symbol and timing information from the PLC receiver.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority based on European Patent Application No. 20201279.5 filed on October 12, 2020 and US Provisional Application No. 63 / 090,397 filed on October 12, 2020, and the entire contents of these applications are incorporated herein by reference.

[0002] Technical Field Embodiments relate to audio systems, and more particularly to clock synchronization for transmitting digital audio and power via a common conductor.

Background Art

[0003] The transmission of digital audio data via Ethernet has long been a subject of discussion and development in the audio industry. The most common current approach is defined by the AES67 standard, which defines the interoperability between Audio - over - Internet - Protocol (IP) and Audio - over - Ethernet (AoE). This approach provides a mechanism for transmitting audio sample streams and audio clocking for restoring, decrypting, and time - aligning samples at the audio endpoints. To establish a reliable technique for synchronizing audio clocks via Ethernet, AES67 utilizes the IEEE1588 standard for Precision Time Protocol (PTP) packets. This technique is a packetized clock format in which an endpoint (slave) can receive specific PTP packets and ultimately synchronize to the master clock transmitted from the master transmitter. The AES67 standard and other methods transmit and receive clock information based on Ethernet packets so that an endpoint (slave) can synchronize to the master clock.

[0004] Along with the development of AoE, power line communication (PLC) technology has also evolved significantly over the past decade, now reliably demonstrating 1-gigabit data transmission performance over standard AC mains power line infrastructure. The basic approach used in PLC devices is to transmit digital data using multiple frequencies well above the baseband power transmission spectrum. This makes it possible for two transmission paths—the power path and the digital data path—to coexist on the same power line or speaker cable infrastructure. PLC technology transmits digital data over basic two-conductor power lines based on digital communication techniques such as orthogonal frequency division multiplexing (OFDM) and bipolar phase shift keying (BPSK). Such technologies fundamentally require synchronization between the master transmitter and the downstream endpoint (slave). Therefore, current PLC standards (e.g., HomePlug AV2, ITU-T, G.Hn, and IEEE 1901-2010) require a robust mechanism for establishing clock synchronization between transmit and receive nodes present on the power line bus.

[0005] Generally, the AES67 approach does not work well when receiving Ethernet packets with latency or jitter, as seen when passing such packets through PLC devices. Therefore, systems using packet-based clock synchronization schemes such as AES67 are unreliable when passing through PLC transmit / receive infrastructure. [Overview of the Initiative]

[0006] The embodiment includes a distributed amplification and packetized audio transmission system for clock synchronization and alignment between an audio / power source and a plurality of endpoints having dedicated amplifiers and speakers. Ethernet audio signals are coupled 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 that restores the master clock used by the endpoint's Ethernet audio receiver to ensure reliable clock synchronization between the source clock and the endpoint clock. The transmitted PLC signals may include Precision Time Protocol (PTP) packets. The endpoints may adjust and re-timestamp the PTP packetized clock based on symbol and timing information from the PLC receiver.

[0007] The embodiment also includes a distributed amplifier audio speaker system having an audio source that transmits audio and power via a common conductor to a plurality of endpoints, each having a speaker for playing audio. The audio source may be an Ethernet audio transmitter connected to a power line communications (PLC) transmitter and a master clock. The master clock is connected to both the Ethernet audio transmitter and the PLC transmitter and generates a master clock signal for both. The PLC transmitter is configured to generate a PLC encoded signal containing audio and provide it to the plurality of endpoints. Each endpoint includes a PLC receiver connected to an Ethernet receiver connected to a speaker and receives the PLC encoded signal. The master clock signal is reconstructed from the PLC encoded signal and synchronizes the Ethernet receiver with the Ethernet transmitter. [Brief explanation of the drawing]

[0008] In the following drawings, similar elements are indicated by the same reference numerals. The following drawings illustrate various examples, but one or more embodiments are not limited to those shown.

[0009] [Figure 1] Figure 1 shows a distributed amplifier (drivepack) speaker system implementing one or more embodiments of a clock synchronization scheme for transmitting digital audio over baseband power lines.

[0010] [Figure 2] Figure 2 shows the components of the control unit and speaker unit for the distributed amplification system of Figure 1 in several embodiments.

[0011] [Figure 3] Figure 3 shows exemplary spectral assignments for power and audio signals transmitted through the same conductor in several embodiments.

[0012] [Figure 4] Figure 4 shows the distributed amplifier system of Figure 1 implemented using standard off-the-shelf components in an exemplary embodiment.

[0013] [Figure 5] Figure 5 shows the addition of endpoint audio clock synchronization via power line communication (PLC) clocking to the distributed amplifier system of Figure 4 in several embodiments.

[0014] [Figure 6] Figure 6 is a flowchart illustrating how a PLC clocking system can provide endpoint audio clock synchronization in several embodiments.

[0015] [Figure 7]Figure 7 shows an endpoint audio clock synchronization system using Precision Time Protocol (PTP) updates in several embodiments.

[0016] [Figure 8] Figure 8 is a flowchart illustrating a method for providing endpoint audio clock synchronization by PLC PTP update in several embodiments. [Modes for carrying out the invention]

[0017] The embodiments relate to a system and method for clock synchronization for transmitting digital audio over baseband power lines or speaker cables in an audio playback system. Any of the embodiments described herein may be used alone or in any combination. Various embodiments may be motivated by various shortcomings of the current known solutions that may be discussed herein, but the embodiments do not necessarily address any of those shortcomings. Each embodiment may address different shortcomings, and some shortcomings may be addressed only partially.

[0018] Distributed amplification speaker system Over the past few years, developments have progressed in transmitting packetized digital audio data over power lines and speaker cables, resulting in systems that significantly simplify wiring, improve fidelity and performance, and lower costs. One such development is the distributed amplification or "drive pack" system. In this system, multi-channel digital audio data and power signals reside on speaker wiring that is routed to each drive pack located at the position of each speaker. These drive packs can demodulate and decode the desired audio channels and restore the power signals. These power signals are then used to drive each speaker. In one embodiment, this technology establishes a reliable digital data link between a master transmitter and downstream receivers based on the concept of power line communication (PLC) technology. Power transmission and restoration are achieved using audio band signals and modulation techniques. The overall goal of this system is to create a speaker amplification and driving system that allows multiple speakers to be daisy-chained over a single cable, and furthermore, allows each speaker to play its own content material.

[0019] FIG. 1 shows a distributed amplifier speaker system implementing one or more embodiments of a clock synchronization scheme for transmitting digital audio and power over a common baseband power line or speaker cable. As shown in FIG. 1, system 100 is a multi-channel speaker system having an arbitrary number (N) of speakers 110. Instead of having one amplifier, one power supply, and separate dedicated cables for each speaker channel as in conventional speaker connections, system 100 includes one main amplifier and corresponding control unit 102, one cable run (“bus”) 106, and one power supply 104 for all N speaker channels 110. To achieve this simplification in the power and signal distribution infrastructure, a dedicated speaker unit 108, called a “drive pack,” which receives and recovers the power and audio signals generated by control unit 102, is associated with each speaker channel. The number of channels N can be any practical number of channels determined by system requirements. In the case of a standard surround sound setup, N can be 7 or 9. On the other hand, in the case of a full space audio (e.g., Dolby Atmos®) system with height speakers, N can be on the order of 16 or 24 channels or more.

[0020] The architecture of system 100 enables the distribution of audio power and signals to multiple speakers without using high channel count amplifiers and multiple point-to-point cables. This reduces the number of audio power amplifier channels and independent speaker cables, while allowing each speaker to have independent drive (i.e., separate audio signals present at each speaker). In one embodiment, amplifier 104 can be a power supply implemented as a customized or standard audio amplifier for transmitting power signals on bus 106, and control unit 102 includes an N-channel digital audio transceiver and audio signal generator for adding digital audio signals on the same bus cable.

[0021] The digital audio transceiver of unit 102 transmits a plurality of digital audio streams driven by the power signal generated by audio amplifier 104. These two signal streams (power and data) are transmitted simultaneously via bus 106 and received by the small electronic speaker unit 108 built into (or connected in proximity to) each speaker 110. The speaker unit 108 restores the power, receives the digital audio stream, and drives the speaker with the selected signal. In one embodiment, bus cable 106 is a single standard two-conductor speaker cable of standard gauge (e.g., 10 - 20 gauge) and can be used to send multiple channels of digital audio and appropriate power to independent speakers connected to the same two-conductor cable. That is, it is possible to wire multiple speakers in a daisy chain or in parallel while enabling each speaker to reproduce an independent audio channel (i.e., different signals and volumes). The bus cable can be implemented as a simple two-conductor speaker cable, or a three-conductor cable such as an AC power cable where one conductor is the earth ground, or any other similar simple conductor cable. Instead of a conventional speaker cable (i.e., a twisted pair cable), a solid core Romex (typical AC wiring cable) cable may be used.

[0022] In one embodiment, a part of power supply 104 can be implemented as a standard power amplifier. Additionally or alternatively, it may be implemented as a dedicated baseband AC power supply or DC power supply that is similar to an audio amplifier but has much higher power efficiency and power throughput. In this embodiment, the system will be very suitable for maximum power transmission, minimum power loss, and lowest cost.

[0023] Speaker 110 may represent a single driver or transducer within a single enclosure (cabinet), a multi-driver speaker with different transducers handling different audio components (e.g., woofer, midrange, tweeter), or a speaker array. In one embodiment, speaker unit 108 may also include additional circuitry for independently driving each speaker component (e.g., woofer, tweeter, etc.) in a bi-amplification manner. Both the control unit and each speaker unit include a transceiver stage that enables bidirectional data flow between the control unit's digital audio transceiver and multiple speakers present on the bus. Thus, other information can be propagated to and from the speakers. For example, telemetry (down angle, temperature, etc.) can be reported from the speakers, or setup information can be transmitted to individual speakers (volume adjustment, motorized pan-tilt angle adjustment, etc.). In a system utilizing bi-amping within a speaker, it is possible to derive two (or more) audio signals by sending a single audio stream to the speaker unit 108, and the speaker unit employs signal processing to derive two (or more) audio signals from a single input stream. Alternatively, the control unit 102 may send multiple streams directly to individual amplification stages within the speaker unit 108.

[0024] Figure 2 shows the components of the control unit and speaker unit for the distributed amplification system of Figure 1 in several embodiments. The architecture of system 200 subdivides the audio amplification process so that the power supply is selected to be physically isolated from the individual output stages and to effectively supply AC stimulation to power the multiple output stages.

[0025] In one embodiment, power supply 204 includes a standard audio amplifier to power other distributed audio output stages. This helps achieve efficiency through component reuse by eliminating the power supply, which is one of the biggest cost factors in any audio amplifier design. Audio power amplifiers are typically designed as AC-DC power supplies and supply power to one or more low-impedance transistorized output stages. Most audio amplifiers are designed as 2- to 4-channel devices, with a single power supply (AC / DC offline power supply) fanned out to power the output stages. Thus, the power supply can be implemented as a standard audio amplifier that produces a controlled audio band, AC waveforms, and provides regulatory compliance (NRTL, CE, FCC, safety isolation, etc.).

[0026] In the embodiment shown in Figure 2, the modulated input waveform applied to the power supply audio amplifier is generated by an audio signal generator in the control unit 202. Since the output of the power supply amplifier is used solely to distribute power to various output stages, this power supply amplifier is not subject to high fidelity or spectral purity requirements. Similar to the signals present in a typical AC mains 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 an existing audio amplifier to function as the power source for the distributed array of output stages, with a single cable 206 powering multiple output stages 210. As with any parallel power distribution system, the overall power consumption must be carefully determined and managed so that the power supply amplifier and cabling adequately supply the power required by the sum of all distributed output stages connected to the line. If more power is required, or if more parallel output stages are connected to the line, the power supply amplifier can be bridged or paralleled with similar amplifiers. Examples of power supplies include cinema-grade amplifiers that supply 800W per channel at 4Ω and 1000W per channel at 2Ω (e.g., the Crown DSi2000), or any amplifier with similar ratings.

[0027] As shown in System 200, the control unit 202 generates a digital audio signal that includes immersive audio having both channel-based and object-based audio components. In the example in Figure 2, an interface connects the control unit 202 to, for example, a renderer (e.g., CP850) 201. This interface and processor provide a signal to an audio signal generator that stimulates a power supply 204. The digital audio transmitter 203 of the control unit 202 outputs the digital audio signal directly to the power supply output so that both the power and digital audio signals are carried on the bus cable 206. The control unit also includes appropriate circuitry to align the power and data to ensure that the power and data are transmitted properly across the bus in terms of timing, amplitude, and phase.

[0028] While embodiments relating to immersive or adaptive audio applications are illustrated, any suitable audio format can be used. Furthermore, depending on the type of interface provided in the control unit 202, the input audio may be straight digital audio, hybrid audio, pure channel-based audio, pure object-based audio, etc. If analog audio is provided, the system may include an integrated or separate analog-to-digital converter to provide a digital audio signal to stimulate the power supply 204 and a digital audio input to the bus cable 206. In one embodiment, the control unit 202 outputs digital data primarily to be coupled to the power supply output, while the input to the power supply is stimulated with an analog audio band-modulated signal (i.e., a sine wave, pink noise, a combined audio signal, etc.). Thus, the digital data is primarily wired / coupled to the power supply output, while the input to the power supply can be controlled by digital or analog technology.

[0029] In one embodiment, where the power supply 204 includes a standard or other type of amplifier, the system 200 may be configured to have lines connected to the amplifier's output to inject a digital data stream into speaker wires or bus cables 206, in addition to generating a power stimulus signal to the amplifier. The digital data stream wiring can also be used as a sense line for the controller via an A / D (analog / digital) circuit. The controller 202 can then compare the input and output signals coming from each amplifier channel. This allows for the implementation of additional functions in software (or equivalent circuitry) such as gain correction adjustment (for example, if the user changes the amplifier gain, the system can adjust and compensate the input signal), fault monitoring for distortion, fault monitoring for present signals, automatic system configuration for changing the gain structure, and other similar functions.

[0030] In one embodiment, the bus cable 206 connecting the control unit 202 to each speaker unit 208 is a single two-conductor speaker cable (or a three-conductor power cable, etc.). Data is transmitted over the bus using the Internet Protocol (IP) specification, although other protocols are also possible. Sufficient bandwidth and channel isolation are provided using a standard power line communication format so that channelized audio information generated by the control unit can be delivered to the output stages. Examples of standard power line communication protocols include IEEE 1901 (HomePlug AV1.1) and the G.hn protocol. However, the embodiments are not limited thereto, and other standardized protocols or proprietary technologies can be used to transmit digital audio information over power cables to deliver independent audio streams to distributed output stages.

[0031] Power signals, digital audio signals, and metadata for audio object control and lighting control are transmitted between the control unit / amplifier and the speaker unit via the same conductor and encoded in different bands in the frequency spectrum. Power and audio signals can be separated by frequency band. For example, the power component could be in a relatively low frequency band between 0 (DC) and 20 kHz, and the digital data components for audio and lighting control could be transmitted in a band spanning, for example, 1 MHz to 100 MHz, but embodiments are not limited thereto. Figure 3 shows exemplary spectral assignments for power and audio signals transmitted via the same conductor in several embodiments. The spectral assignment diagram is shown as signal amplitude (Y axis) 302 versus its frequency (X axis) 304. As shown in Figure 3, the audio band power signal is encoded in the 0 to 20 kHz region, and the digital audio transmission is encoded in the 1.8 MHz to 86 MHz region. Thus, the separation of the power 306 and audio 308 signals is greater than approximately 1.5 MHz. Figure 3 shows exemplary power / audio spectral assignments. The embodiments are not limited thereto, and any other similar spectral assignments may be used to encode audio signals for transmission over a common conductor.

[0032] Figure 4 shows the distributed amplifier system of Figure 1 implemented using standard commercially available components in an exemplary embodiment. For system 400, audio and power signals are propagated between source 401 and endpoint 411 through specific electrical components for each specific sequence and via a common conductor 410. Audio signals originate from the audio block 402 of source 401. The audio is then packetized into an Ethernet audio format (e.g., AES67 or CobraNet) using an audio transmitter (e.g., Dolby CP850, Audio Science Hono 8.0L, etc.) 404. The packetized audio is then sent to a power line communication (PLC) transmitter 406 connected to the output of a baseband power supply (e.g., a crown amplifier) ​​408. The amplifier 408 is driven by the audio signal from source 402, which has been processed by a digital signal processing (DSP) 405. Next, amplifier 408 outputs a power supply signal that is conducted to endpoint electronic devices located at or near speaker 420 via standard two-conductor speaker wiring or other similar conductors or cables 410. The power signal output from amplifier 408 and the packetized audio output from PLC transmitter 406 are combined into the electrically coupled outputs of PLC transmitter 406 and amplifier 408.

[0033] Within endpoint 411, a power line communication (PLC) receiver 412 is connected to the input speaker wiring 410 and is operable to demodulate and restore Ethernet packets. The restored Ethernet packets are then passed to an Ethernet audio receiver 416, which restores the audio stream originating from the original audio source 402. The restored audio is then amplified using a standard or customized Class D amplifier 418 to drive a speaker transducer 420. The amplifier 418 also receives a composite signal transmitted through the conductor 410 as input, which has been adjusted or transformed by a power factor correction (PFC) component 414.

[0034] Figure 4 is provided solely for the purpose of illustrating an exemplary implementation of a distributed amplifier speaker system that includes, or is modified to include, a clock synchronization process. Such exemplary circuits are not intended to be limiting, and other implementations, components, configurations, and signal processing sequences are also possible.

[0035] As mentioned above, current PLC systems may have certain problems regarding the establishment of reliable audio transmission from audio source 402 to endpoint audio receiver 416. The PLC transmit / receive process adds latency and jitter to the packetized digital information, which can lead to decoding errors within the endpoint. Of particular concern is the impact of randomized PLC latency and jitter on the packetized audio clocking infrastructure inherently built into the Ethernet audio scheme used in certain audio over Ethernet systems. PLC latency and jitter can negatively affect the reliable restoration and synchronization of audio clock information packetized within certain AoE streams, potentially leading to transmission failures of Ethernet packetized audio streams over standard PLC devices. Specifically, it was found that certain latency and jitter added to the packetized digital information by the PLC transmit / receive process can cause decoding errors within endpoint 411.

[0036] Accordingly, the embodiment includes a clock synchronization and matching component or system 422 that helps to achieve satisfactory transmission of Ethernet packetized audio streams over standard PLC devices and common conductors (e.g., speaker wiring).

[0037] As shown in Figure 4, the distributed amplifier audio transmission and speaker playback system incorporates a clock synchronization and matching component 422 to help achieve clock synchronization and matching for use in packetized audio transmission over baseband power lines or speaker cables. This component, or the processes implemented therein, helps resolve issues related to clock synchronization failures when transmitting standardized audio packets using power line communication equipment.

[0038] Master clock synchronization method Figure 5 illustrates the addition of endpoint audio clock synchronization via PLC clocking to the distributed amplifier system of Figure 4 in several embodiments. The approach of System 500 provides a stable and reliable clock synchronization method for audio transmission over baseband power lines using a hybrid combination of two communication layers (e.g., AES67 and PLC). System 500 includes a source circuit 401 having an audio source that generates a packetized Ethernet signal for transmission to an endpoint 411 via a conductor 410 for playback through a speaker 420, as described above with respect to Figure 4. In this embodiment, the clock synchronization and matching component 422 is implemented by a clock circuit 502 for source 401 and a clock circuit 504 for endpoint 411.

[0039] In the embodiment shown in Figure 5, a single master clock 502 is used within the main transmitter, which synchronizes the Ethernet audio transmitter 404 with the PLC modulator 406. The downstream endpoint 411 then uses the PLC demodulation receiver 412 to restore and lock the original master clock 502 and supplies this synchronized clock to the Ethernet audio receiver 416. This approach ensures reliable clock synchronization between the master transmitter and all downstream endpoints (slaves). Due to the clock synchronization requirements inherent in modern PLC transmissions utilizing OFDM and BPSK signaling, the master clock supplied to the PLC transmitter is restored by the downstream PLC receiver using a phase-locking method.

[0040] This clocking method also allows for proper time synchronization of the clock edge to the input audio samples recovered from the Ethernet data packets. This is achieved by using PLC telemetry information (received PLC symbol latency and jitter) to adjust the recovered clock edge timing to match the audio sample stream. Thus, the clocking mechanism in Figure 5 achieves two objectives: firstly, to provide clock recovery / synchronization between the source and endpoint (i.e., to ensure phase coherence between the audio source and endpoint), and secondly, to match the clock edge time with the audio sample stream. These characteristics enable reliable audio transmission using packetized audio over baseband power lines and speaker cables.

[0041] Figure 6 is a flowchart illustrating how endpoint audio clock synchronization is provided via a PLC clocking system (e.g., via the system in Figure 5) in several embodiments. Process 600 begins by providing a single master clock within or using the Ethernet transmitter on the source side (602). This master clock synchronizes the Ethernet transmitter with the PLC modulator on the source side (604). The synchronized PLC signal is then transmitted to the endpoint side via a common conductor (e.g., speaker wiring) (606). The PLC demodulated receiver at the endpoint receives the PLC signal and restores and locks the original master clock (608). This restored original master clock signal is then provided to the Ethernet audio receiver at the endpoint (610). In this way, the clock of the master Ethernet transmitter is synchronized with the Ethernet receiver at the endpoint. In a speaker system with multiple (e.g., 8 to 64) speakers, this method ensures that the clocks are reliably synchronized between the master transmitter and all speaker endpoints.

[0042] As described above with respect to Figure 5, the PLC signal sent from the source to the endpoint is also used to properly time-match the clock edge to the input audio samples recovered from the Ethernet data packets. Therefore, in process 500, the transmitted synchronized PLC signal (transmitted in step 606 of the flowchart in Figure 6) is also used to properly adjust the recovered clock edge timing to match the audio sample stream (matched in step 612 of the flowchart in Figure 6). This is done using the received PLC symbol latency and jitter (PLC telemetry data) in the received PLC signal. By monitoring the inter-symbol latency, delay, and nominal jitter performance of the physical layer (i.e., speaker cable routing), the PLC receiver can precisely adjust and match the audio sample frames to ensure robust recovery of the audio sample stream.

[0043] How to update Precision Time Protocol (PTP) In another embodiment, audio clock synchronization between the source and endpoint can be achieved by PLC Precision Time Protocol (PTP) updates. The following description of this further embodiment focuses on the differences from the previously described embodiment. Therefore, features common to both embodiments are omitted in the following description, and unless otherwise specifically stated in the following description, it should be assumed that the features of the described embodiment are implemented, or at least implementable, in the further embodiment.

[0044] In this embodiment, the endpoint Ethernet receiver adjusts the PTP packetization clock information and re-timestamps it based on symbol timing information known within the PLC receiver. This technique requires that the endpoint PLC has accurate timing information for its input symbols, as in the previously described embodiment.

[0045] Figure 7 shows an endpoint audio clock synchronization system using PTP updates in several embodiments. The approach of system 700 uses PTP packets 709 used in the IEEE 1588 standard in AES67 format. System 700 includes a source circuit 701 having an audio source for transmission to an endpoint 711 via a conductor 710 for playback through a speaker 720, as described above with respect to Figure 4. In this embodiment, source 701 transmits audio data to the downstream endpoint 711 in the form of PTP packets 709. A PLC receiver 712 holds specific PTP timing data 715. Using this information, the endpoint receiver 711 adjusts the PTP packetized clock information 709 and re-timestamps it based on symbol timing information known within the PLC receiver. The PTP timing data includes precise timing information for its input symbols. In other words, the PLC receiver is configured to monitor the timing of PLC-encoded symbols in order to adjust the PTP packets and re-timestamp them.

[0046] The endpoint PLC 712 measures and provides symbol latency and inter-symbol jitter performance, and then adjusts and / or re-timestamps each PTP packet to address the time-varying latency and jitter aspects of the PLC. Once the PTP packets are adjusted to address the latency and jitter of the PLC, the endpoint Ethernet audio receiver 716 uses an existing PTP clock synchronization scheme to precisely synchronize the endpoint clock with the clock of the source Ethernet audio transmitter 704. In this embodiment, the PLC receiver 712 monitors the symbol timing parameters that will be used by the subsequent re-timing algorithm and modifies the PTP packets as necessary. Similar to the above embodiment, the PLC receiver can monitor the inter-symbol latency, delay, and nominal jitter performance of the physical layer (speaker cable routing), and the PLC receiver can pass this time-skew information to a PTP algorithm that can re-align the clock and audio frame restoration algorithm with the transmitter. In this embodiment, the clock restoration method uses packet-based restoration (e.g., PTP), and the restored clock packets are adjusted to achieve alignment and synchronization, in contrast to the above embodiment which achieves synchronization using a proprietary PLC clock synchronization infrastructure. The master clock is the primary high-frequency time base used to maintain phase coherence between all digital devices in the system. The master clock can typically operate at a frequency of 12 to 100 MHz. In an audio system, the master clock can operate at a multiple of the audio sample frequency. For example, if the audio sample rate frequency is 48 kHz, the master can operate at a frequency of 24.576 MHz, which is 512 times the audio sample frequency. The above PTP method can be considered a method for transmitting and restoring the audio sample clock over a time-varying physical layer (such as Ethernet). Packetized data can experience various delays as packets travel over conventional time-varying physical layers such as Ethernet (i.e., via hubs / switches / routers).Typically, in conventional systems, the varying delay (and jitter) of the conventional power line communication (PLC) physical layer prevents the PTP system from restoring the audio sample clock, resulting in improper operation of PTP transmission over the PLC physical layer. To address this issue, the PTP method of this disclosure synchronizes the PLC physical layer equipment (i.e., PLC transmitter and PLC receiver) with a master clock, and the PLC receiver monitors the latency and jitter of the received PLC encoded data (e.g., PLC symbols transmitted over physical power lines). The PLC receiver can then use this timing information (e.g., latency and jitter of the PLC symbols) to adjust the timing of PTP packets and re-timestamp them. This ensures that PTP packets are properly clocked without gaps or dropouts, allowing the audio stream to be played back correctly.

[0047] Figure 8 is a flowchart illustrating how endpoint audio clock synchronization is provided through PLC PTP updates in several embodiments. As shown in Figure 8, process 800 begins with the endpoint receiving a PLC signal from the source side (802). The endpoint PLC receiver measures and provides symbol latency and inter-symbol jitter performance using its internal clock restoration and symbol timing monitoring algorithms (804). Next, a downstream algorithm adjusts or re-timestams each PTP packet to accommodate the time-varying latency and jitter aspects of the PLC (806). This algorithm modifies the PTP packet timestamp to adjust for the symbol latency measured on the nominal physical layer and can be executed within an Ethernet audio receiver integrated circuit or a programmable logic unit. Once the PTP packets are adjusted to accommodate the PLC latency and jitter, the endpoint Ethernet audio receiver uses the existing PTP clock synchronization scheme to precisely synchronize the endpoint clock to the master (source) transmitter clock (808). In this embodiment, the endpoint PLC receiver needs to monitor the symbol timing parameters used by the subsequent re-timing algorithm to modify the PTP packets as needed.

[0048] This PLC PTP update embodiment can be used in combination with the master clock transmission / restoration / synchronization scheme described in Figure 6. Therefore, the signal received by the endpoint in step 802 may be a standard audio / power signal transmitted along conductor 410, as shown in Figure 4, or a master clocked signal, as shown in Figure 5.

[0049] The embodiments can be used to reproduce any suitable type of audio format, including stereo, surround sound, object-based audio, or spatial (immersive) audio content. An exemplary immersive audio system and associated audio format is the Dolby Atmos platform. Such systems incorporate a height (up / down) dimension, which can be implemented as 5.1, 7.1, 9.1 surround systems, or similar surround sound configurations (e.g., 11.1, 13.1, 19.4, etc.). Generally, these speakers can be used to produce sound designed to be emitted more or less accurately from any position within the listening environment. Immersive audio can be used in a variety of locations, such as cinemas, auditoriums, and homes. Thus, endpoint speakers can be placed at any suitable position and distance from the audio source. Such speakers can also be implemented in any suitable configuration, such as single or multi-way speakers, soundbars, standing or bookcase speakers, LFE (low-frequency effect) speakers, height speakers, etc.

[0050] Furthermore, the embodiments can be used with any suitable power line (AC mains) infrastructure. In home applications, the direct amplification system can enable multi-channel audio distribution throughout the home without burdening Wi-Fi or other wireless infrastructure. Since most powered speakers require some connection to the AC mains, reliable audio transmission can be achieved directly without adding audio signal wiring. Thus, the embodiments of the direct amplification audio system described herein can be used in any suitable location or application, such as movie theaters, home cinemas, live venues, auditoriums, industrial facilities, military facilities, and theme parks.

[0051] While the implementation examples described concern a specific component such as the Dolby Cinema Processor CP850, the embodiments are not limited to this, and any similar or other suitable component may be used.

[0052] Unless otherwise specified in the context, throughout this specification and the claims, words such as “includes,” “equip,” and “compris,” shall be interpreted in an inclusive sense, not in an exclusive or exhaustive sense. Terms using singular or plural numbers also include plural or singular, respectively. When the term “or” is used in relation to a list of two or more items, that term includes all of the following interpretations: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0053] While one or more implementations have been described as examples of specific embodiments and from the viewpoint of specific embodiments, it goes without saying that these implementations are not limited to these. The description is intended to cover a variety of modifications and similar arrangements, as will be apparent to those skilled in the art. Therefore, the scope of the appended claims should be given the broadest possible interpretation to encompass all such modifications and similar arrangements.

[0054] Various aspects of the present invention can be understood from the following enumerated example embodiments (EEEs):

[0055] EEE1 An audio source that transmits audio and power to a plurality of endpoints via a common conductor, each endpoint having a speaker for playing the audio, the audio source includes an Ethernet audio transmitter connected to a power line communications (PLC) transmitter, and a master clock connected to both the Ethernet audio transmitter and the PLC transmitter and generating a master clock signal for both thereof, the PLC transmitter generating a PLC encoded signal including the power and audio and providing it to the plurality of endpoints, An endpoint among the plurality of endpoints that receives the PLC encoded signal, and includes a PLC receiver connected to an Ethernet receiver connected to a speaker, wherein the PLC receiver reconstructs the master clock signal from the PLC encoded signal, thereby synchronizing the Ethernet receiver with the Ethernet transmitter; A distributed amplifier audio speaker system equipped with [specific feature].

[0056] EEE2 The system according to EEE1, wherein the PLC encoded signal includes PLC telemetry information including PLC symbol latency and jitter, and the endpoint further adjusts the restored master clock signal to match the transmitted audio sample stream of the audio.

[0057] EEE3 The system according to EEE2, wherein the power includes an audio band power signal encoded in a first frequency spectral range, and the audio sample stream is encoded in a second frequency spectral range separated from the first frequency spectral range by a predetermined minimum frequency difference.

[0058] EEE4 The Ethernet audio transmitter is a system as described in EEE1, utilizing either the AES67 or CobraNet Ethernet audio format.

[0059] EEE5 The PLC encoded signal is a system as described in EEE4, which includes one of the HomePlug AV2, ITU-T, G.HN, or IEEE1901-2010 transmission standards.

[0060] EEE6 The system according to any one of EEE1 to 5, wherein each endpoint of the plurality of endpoints comprises a dedicated amplifier connected in close proximity to each speaker for reproducing at least one audio component of the transmitted audio signal.

[0061] EEE7 The system according to any one of EEE1 to 6, wherein the dedicated amplifier is configured to demodulate and decode the audio channels of the transmitted audio, restore power signals from the transmitted power, and drive each of the speakers.

[0062] Eee8 The system according to EEE7, wherein the audio source is connected to the endpoint via a two-conductor speaker wire.

[0063] EEE9 A system according to any one of EEE1 to 8, further comprising a control unit having a multi-channel digital audio transceiver and an audio signal generator connected to a Class D amplifier that transmits the audio and power to the plurality of endpoints, wherein the audio includes at least one of stereo, surround sound, object-based audio, or immersive audio content, and the immersive audio content includes both object-based audio and channel-based audio components.

[0064] EEE10 A method for synchronizing the timing of an audio source and multiple endpoints, each having a speaker for playing audio content, To provide a single master clock within the Ethernet transmitter on the audio source side, The master clock is synchronized with the Ethernet transmitter having the power line communication (PLC) modulator of the audio source, Transmitting a synchronized PLC signal to one of the multiple endpoints via a common conductor, The endpoint PLC demodulation receiver receives the PLC signal, Reconstructing the master clock from the received PLC signal, The restored master clock signal is provided to the Ethernet audio receiver at the endpoint to synchronize the clock of the Ethernet transmitter with the Ethernet receiver at the endpoint, A method that includes

[0065] EEE11 The method according to EEE10, wherein the PLC signal includes PLC telemetry information including PLC symbol latency and jitter, and the method further comprises adjusting the recovered master clock at the endpoint to match the audio sample stream transmitted to the plurality of endpoints by the audio source.

[0066] EEE12 The method according to EEE11, wherein the power includes an audio band power signal encoded in a first frequency spectral range, and the audio sample stream is encoded in a second frequency spectral range separated from the first frequency spectral range by a predetermined minimum frequency difference.

[0067] EEE13 The Ethernet audio transmitter utilizes either the AES67 or CobraNet Ethernet audio format, and the PLC encoded signal further includes any of the HomePlug AV2, ITU-T, G.HN, or IEEE1901-2010 transmission standards, as described in any of EEE10 to 12.

[0068] EEE14 The method according to any one of EEE10 to 13, wherein each endpoint of the plurality of endpoints comprises a dedicated amplifier connected in close proximity to each speaker for reproducing at least one audio component of the audio signal transmitted by the audio source, the dedicated amplifier demodulates and decodes the audio channels of the transmitted audio, restores a power signal from the transmitted power, and drives each speaker.

[0069] EEE15 An audio source that transmits audio and power to multiple endpoints via a common conductor, each endpoint having a speaker for playing the audio, the audio source includes an Ethernet audio transmitter connected to a power line communications (PLC) transmitter, and a master clock connected to both the Ethernet audio transmitter and the PLC transmitter, which generates a master clock signal, the PLC transmitter generates PLC encoded signals including the power and audio to the multiple endpoints, A Precision Time Protocol (PTP) component that transmits the PLC encoded signal using the PTP signal component, An endpoint among the plurality of endpoints that receives the PLC encoded signal and PTP signal component, wherein the endpoint includes a PLC receiver connected to an Ethernet receiver connected to a speaker, the PLC receiver holds specific PTP timing data, uses the data to adjust the PTP packetized clock information received from the audio source and PTP component, performs a re-timestamp, and thereby compensates for any latency and jitter present in the transmitted audio signal, A distributed amplifier audio speaker system equipped with [specific feature].

[0070] EEE16 The system according to EEE15, wherein the endpoint further monitors the symbol timing parameters in the transmitted audio signal and modifies the received PTP packet using one or more retiming algorithms to achieve a minimum level of clock synchronization between the audio source and the endpoint.

[0071] EEE17 The PTP packet conforms to the IEEE 1588 standard in AES67 format, and is a system described in any of EEE15 to 16.

[0072] EEE18 The system according to EEE15, wherein each of the plurality of endpoints includes a dedicated amplifier connected in close proximity to each speaker for reproducing at least one audio component of the transmitted audio signal.

[0073] EEE19 The system according to any one of EEE15 to 18, wherein the power includes an audio band power signal encoded in a first frequency spectral range, and the audio sample stream is encoded in a second frequency spectral range separated from the first frequency spectral range by a predetermined minimum frequency difference.

[0074] EEE20 The system according to any one of EEE15 to 19, wherein the dedicated amplifier is configured to demodulate and decode the audio channels of the transmitted audio, restore power signals from the transmitted power, and drive each of the speakers.

Claims

1. Audio source and Multiple endpoints, A distributed audio speaker system comprising, Each of the aforementioned endpoints is Speakers configured to play audio, An Ethernet audio receiver connected to the speaker, A power line communication (PLC) receiver connected to the Ethernet audio receiver, Equipped with, The audio source is configured to transmit the audio and power to the plurality of endpoints via a common conductor. The aforementioned audio source is A power source that generates the aforementioned power, A PLC transmitter connected to the output of the aforementioned power supply, An Ethernet audio transmitter connected to the PLC transmitter, A master clock connected to the PLC transmitter and the Ethernet audio transmitter, Equipped with, The master clock is configured to generate a master clock signal for both the Ethernet audio transmitter and the PLC transmitter. The PLC transmitter is configured to generate a PLC encoded signal including the audio and to transmit the PLC encoded signal through the common conductor. One of the plurality of endpoints is configured to receive the PLC encoded signal and the power, The PLC receiver of the endpoint is configured to reconstruct the master clock signal from the PLC encoded signal and to synchronize the Ethernet audio receiver of the endpoint with the Ethernet audio transmitter of the audio source. The PLC receiver is configured to monitor the PLC encoded signal, acquire PLC telemetry information including PLC symbol latency and jitter from the PLC encoded signal, and adjust the restored master clock signal using the PLC telemetry information to match the audio sample stream to the transmitted PLC encoded signal. Distributed audio speaker system.

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

3. The system according to claim 1 or 2, wherein the Ethernet audio transmitter utilizes either the AES67 or CobraNet Ethernet audio format, and the PLC encoded signal includes any of the HomePlug AV2, ITU-T, G.HN, or IEEE 1901-2010 transmission standards.

4. Each of the plurality of endpoints is equipped with a dedicated amplifier connected in close proximity to each speaker for reproducing at least one audio component of the transmitted audio. The PLC receiver is configured to demodulate and decode the audio channel of the transmitted PLC encoded signal. The dedicated amplifier is configured to amplify the decoded audio channel, restore the power signal from the transmitted power, and drive each of the speakers. The audio source is connected to the endpoint via a two-conductor speaker wire. The system according to any one of claims 1 to 3.

5. The control unit further comprises a multi-channel digital audio transceiver and an audio signal generator connected to an amplifier that transmits the audio and power to the plurality of endpoints, The system according to any one of claims 1 to 4, wherein the audio includes at least one of stereo, surround sound, object-based audio, or immersive audio content, and the immersive audio content includes both object-based audio and channel-based audio components.

6. A method for synchronizing the timing of an audio source and a plurality of endpoints having speakers for playing audio, Ethernet audio receivers connected to the speakers, and power line communications (PLC) receivers connected to the Ethernet audio receivers, wherein the audio source is configured to transmit audio and power to the plurality of endpoints via a common conductor, the audio source includes a power supply for generating the power, a PLC transmitter connected to the output of the power supply, an Ethernet audio transmitter connected to the PLC transmitter, and a master clock connected to the PLC transmitter and the Ethernet audio transmitter, the method is: The power is generated by the aforementioned power supply, The PLC transmitter generates a PLC encoded signal including the audio, The master clock generates a master clock signal for both the Ethernet audio transmitter and the PLC transmitter. The master clock signal is used to synchronize the Ethernet audio transmitter with the PLC transmitter, The PLC transmitter transmits the PLC encoded signal to one of the multiple endpoints via the common conductor, The PLC receiver of the endpoint receives the PLC encoded signal, The PLC receiver recovers the master clock signal from the received signal, The restored master clock signal is provided to the Ethernet audio receiver of the endpoint to synchronize the Ethernet audio transmitter of the audio source and the Ethernet audio receiver of the endpoint, The PLC receiver monitors the PLC encoded signal and obtains PLC telemetry information, including PLC symbol latency and jitter, from the PLC encoded signal. The PLC receiver adjusts the restored master clock signal using the PLC telemetry information to match the audio sample stream transmitted to the plurality of endpoints by the audio source, method.

7. The method according to claim 6, wherein the power includes an audio band power signal encoded in a first frequency spectral range, and the audio sample stream is encoded in a second frequency spectral range separated from the first frequency spectral range by a predetermined minimum frequency difference.

8. The method according to claim 6 or 7, wherein the Ethernet audio transmitter utilizes either the AES67 or CobraNet Ethernet audio format, and the PLC encoded signal further includes any of the HomePlug AV2, ITU-T, G.HN, or IEEE 1901-2010 transmission standards.

9. Each of the plurality of endpoints is equipped with a dedicated amplifier connected in close proximity to each speaker for reproducing at least one audio component of the audio transmitted by the audio source. The PLC receiver is configured to demodulate and decode the audio channel of the transmitted PLC encoded signal. The dedicated amplifier is configured to amplify the decoded audio channel, restore the power signal from the transmitted power, and drive each of the speakers. The method according to any one of claims 6 to 8.

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