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Sonos Defeats Denon HEOS Again: Understanding the Patent Lawsuits

Sonos seeks injunction and double damages for D&M's ‘willful infringement’ of Sonos patents in the Denon HEOS line. Judge invalidates another D&M patent.

Sonos Defeats Denon HEOS Again: Understanding the Patent Lawsuits
A third D&M patent is invalidated after the company asserts infringement claims in a countersuit against Sonos. Seven out of nine D&M patent infringement claims have been dismissed so far. Sonos seeks double damages and injunction order after D&M was found guilty of willfully infringing three Sonos patents to create a "Sonos killer" with the Denon HEOS wireless audio line.
Credit: CE Pro Photo Illustration

Julie Jacobson · February 26, 2018

It was a bad week for Denon Electronics, LLC and its HEOS line of wireless multiroom audio systems. The D&M Holdings unit, now owned by Sound United, was sued by Sonos in 2014 on four patent infringement claims. In December 2017, the jury ruled against Denon on three of those claims, ordering the company to pay Sonos $2 million for past breaches dating back to the HEOS product launch in 2014 through December 2016.

Last week, Sonos filed a claim to extend damages through December 2017, alleging Denon continues to infringe on the patents in question. (Relevant Sonos and D&M patents are summarized below.)

Furthermore, Sonos is asking to “enhance” damages by at least 2x because Denon’s infringement was deemed “willful” by the jury last year, and because Denon has engaged in other “inappropriate behavior” throughout the proceedings.

Sonos also requests a permanent injunction against Denon’s infringing products, or else ongoing royalties of at least twice what the jury effectively awarded last year.

“D&M became desperate and would stop at nothing, including disregarding Sonos’s patent rights, to accomplish its goal of creating a ‘Sonos Killer’ ...."
— Sonos filing seeking double damages and injunction, 2/20/2018

In another blow, a judge invalidated a key D&M patent ('899, involving the storage of user preferences for audio/video playback) on summary judgment -- a highly unusual move. That 2006 patent, and several others owned by D&M, had been filed by Digital Networks North America, parent company of the one-time TiVo rival ReplayTV.

'899 was the third D&M patent to be invalidated by the Court, out of nine patents asserted in "retaliatory" infringement counterclaims against Sonos. Four other patent-infringement claims were withdrawn voluntarily by D&M after the Court issued its claim construction, i.e., how the patents should be interpreted for legal purposes. 

Two others are still in play, but Sonos believes it will prevail in summary judgment on one of the patent-infringement claims. (Patents and dispositions detailed below.)

In its latest filing, Sonos reiterated “evidence” the jury heard regarding the willfulness of Denon’s infringing behavior, particularly in regards to Sonos's '258 patent (method of synchronizing audio zones) and '949 patent (grouping multiple players into a single zone and controlling the volume of all players at once).

  • "[P]rior to developing HEOS, D&M spent ‘a considerable amount of time, money, and energy’ studying Sonos’s technology,  which included numerous detailed “teardowns” of Sonos’s products embodying the patented technology …."
  • “D&M developed a product plan for ‘reproducing the Sonos functionality’ and … acknowledged Sonos was the ‘benchmark’ for HEOS.”
  • “[P]art of D&M’s plan to make Sonos-copy products included reproducing Sonos’s dynamic-grouping, synchronization, and group-volume control technology, which D&M internally lauded time and again.”
  • “D&M extensively monitored Sonos’s patent activities as part of the development process for the HEOS product line.”
  • “D&M became desperate and would stop at nothing, including disregarding Sonos’s patent rights, to accomplish its goal of creating a ‘Sonos Killer’ to take Sonos’s market share.”
  • “[K]ey personnel responsible for HEOS either ignored Sonos’s patents or evaluated Sonos’s patents but then took no action to avoid infringing them.”
  • “[T]he infringing HEOS features are software-based and … D&M allegedly could have easily and readily implemented alternative synchronization and volume control features that would apparently avoid infringing Sonos’s patents.”
  • “D&M continued to sell HEOS products that infringe the ‘258 and ‘949 Patents, and continued releasing new marketing materials and promoting the HEOS features that infringe those patents.”
  • “D&M’s HEOS Apps included a nearly identical group volume control interface as can be found in Sonos’s patented App. …  [T]he HEOS device’s synchronization mechanism is identical to the mechanism claimed and described in Sonos’s 258 Patent.”
  • “[T]he HEOS product line used a similar naming convention as Sonos’s product line (e.g., “HEOS 1,” HEOS 3,” HEOS 5,” versus Sonos’s “PLAY:1,” “PLAY:3,” “PLAY:5”).”

D&M’s ‘Inappropriate Behavior’

In addition to its willful infringement, Sonos claims, D&M should be penalized for “inappropriate actions [that] caused Sonos to waste time and significant resources” over the course of the proceedings:

Such misconduct establishes a disregard for Sonos and the valuable time of the Court and jury, and disrespect for the judicial process. D&M’s pursuit of these frivolous defenses was nothing more than a desperate and bad faith effort to force Sonos to unnecessarily incur additional expenses and delay Sonos from pursuing this case to final judgment. This type of vexatious strategy during the litigation is an important consideration when deciding whether to enhance damages ….

The 1992 Read v. Portec case gave us the “Read Factors” for determining the egregiousness of an infringer’s behavior. Sonos systematically runs through these factors in its recent filing, starting with the deliberateness of D&M’s infringement in the first place, discussed above.

Other factors include how “close” the case was, the duration of the infringer’s misconduct, and remedial action taken by the infringer.

Sonos says the case against D&M was “not close at all.”

As the plaintiff explains, "[T]he jury found in favor of Sonos in all respects and deliberated for less than 2 hours – while eating lunch and with a delay …. Indeed, the jury’s quick verdict confirms that D&M’s non-infringement and invalidity positions were tenuous at best.”

RELATED: MORE SMART HOME PATENTS AND LAWSUITS

Moreover, Sonos argues that D&M filed multiple disingenuous claims during the three-year process, and lost almost all of them. For example, D&M tried unsuccessfully to disqualify a Sonos lawyer. The company also tried to use the plaintiff’s “inequitable conduct” as a defense, claiming unethical conduct by Sonos’s in-house lawyer. Plus, D&M forced multiple “claim construction” proceedings to try to secure a favorable interpretation of its own patents. During trial, the court censured D&M for presenting “numerous improper claim constructions to the jury ….”

Sonos alleges other Read factors that “weigh in favor of enhancement.” Most importantly, the company claims D&M continued to infringe on Sonos patents after the original lawsuit was filed in 2014, even launching in 2017 two new products (HEOS Bar and HEOS Subwoofer) that are “not colorably different" from Denon's infringing HEOS speakers.

D&M filed a motion in 2016 challenging the patentability of the three Sonos inventions involved in the case, but Sonos prevailed on all claims.

Damages

Sonos calculated the jury award amounted to $36.55 per HEOS unit sold through December 2016 (54,325 units). The per-unit figure includes only the infringements on two patents (‘258 and ‘949) that would be subject to ongoing damages. Sonos would be asking for something like two times that amount as a “’starting point’ for the Court’s ongoing royalty rate analysis.”

In fact, Sonos believes it should be eligible for treble damages because the defendant filed allegedly meritless claims again and again, and “D&M lost nearly every major decision leading up to the trial.”

A preceding 2017 case (Stryker Corp. v. Zimmer, Inc.) awarded treble damages and fees when it was not a close case where “[e]very major decision – from claim construction to post-verdict motions – went against [defendant].”

Sonos draws deep parallels to that case.

The Patents & Dispositions


D&M - asserted patents in counterclaim against Sonos


Apparatus, method and database for control of audio/video equipment (7,995,899) - 8/9/2011 - INVALIDATED (35 U.S.C. § 101 - not patentable)

Acquired Digital Networks North America, which filed in 2006.

Control of audio/video equipment is provided by an apparatus constructed like a computer, with audio and video subsystems. The audio subsystem includes a programmable analog mixer and several analog and digital multiplexers to route and mix multiple inputs to multiple outputs. Databases are stored in computer mass storage to record preferences for playback of digital versatile discs, compact discs and audio files stored in the mass storage device, such as MP3 files. The playback preferences may include video output format, language, surround sound mode, etc. for DVDs and surround sound effects for CDs and audio files. 

History of Denon, D&M Patents

In the Sonos vs. D&M Holdings case, several of the patents in question were acquired by D&M through its 2003 acquisition of Escient Convergence and OpenGlobe, two pioneers in media management.

D&M closed those businesses in 2015.

Additional patents were acquired from Digital Networks North America, parent company of ReplayTV, a formidable TiVo competitor in the early days.

D&M acquired ReplayTV out of bankruptcy in 2003, and sold the assets to DirecTV in 2007. In 2015, DNNA filed for chapter 7 bankruptcy.


Stream based compressed file download with interruption recovery (7,343,435) - 3/11/2008 - INVALIDATED (35 U.S.C. § 101 - not patentable)

Acquired from Digital Networks North America, which filed in 2003.

A system and method are provided for storing and using recovery state information during a data stream transfer, such as a download. During the download of compressed, archived data, the system tracks the position of the last file boundary and the position of the last compression block boundary before the last file boundary, and the system stores this information as a recovery state. If the download is interrupted, the system uses the recovery state information to resume the download at an efficient location in the data stream.


Method for stream based compressed file download with interruption recovery and further decompressing and de-archiving data in filesystem (7,734,850) - 6/8/2010 - STILL IN PLAY

Acquired from Digital Networks North America, which filed in 2008.

A system and method are provided for storing and using recovery state information during a data stream transfer, such as a download. During the download of compressed, archived data, the system tracks the position of the last file boundary and the position of the last compression block boundary before the last file boundary, and the system stores this information as a recovery state. If the download is interrupted, the system uses the recovery state information to resume the download at an efficient location in the data stream.


Automatic assignment and tuning of radio call letters to radio presets (6,539,210) - 3/25/2003 - WITHDRAWN following claim construction (one claim invalidated for being indefinite)

Acquired from Openglobe, which filed in 2000.

Broadcast signals are detected and matched with signal information, such as call letters, genre and geographical location for corresponding signal sources, based on the geographical location of the receiver and the frequency at which the signals are broadcast. The signal information is stored with signal and medium selection data, so that signal sources provided via different communication media, such as broadcast radio and Internet streaming audio, can be accessed, sorted, selected and displayed together. Thus, a user can group for display information about signal sources transmitting a type of music that the user enjoys, via any communication medium that the receiver supports. Also, a currently selected signal source and communication medium can be matched with a different communication medium for the same source, so that if the received signal deteriorates, the receiver can switch to the different communication medium for receipt of the same signal.


Remote control of electronic devices (6,469,633) - 10/22/2002 - WITHDRAWN following claim construction

Acquired from Openglobe, which filed in 1998.

An apparatus controls electronic devices, via radio frequency (RF) transmitter and receiver for communication between the apparatus and a user, a central processing unit (CPU) executing software for handling the conversion of an RF signal from the user into a two dimensional location (an X, Y coordinate system) and conversion into a series of remote control commands for transmission to a series of devices equipped for remote control. The user can control the electronic devices of an electronic system, for example a home entertainment system (which might include, by way of example, a television, a DSS or satellite receiver, a CD player, a video recorder, a video disc player, a radio tuner, an amplifier, a tape deck, an audio video preamplifier or a combination of one or more of the foregoing). The CPU also executes software which digitizes real time video and combines it with computer graphics for display.


Sonos has big head start, but integrators embrace HEOS

CE Pro 100 companies (2017) spec Sonos more than any other wireless audio brand, but Denon HEOS is off to a good start after just three years on the market. Integrators appreciate the dealer-friendly brand because it was built from the ground up for the custom installation market. HEOS supports high-res audio, and integrates fully with popular home automation systems via an open API.

Method and apparatus for remotely controlling a receiver according to content and user selection (7,305,694) - 12/4/2007 - INVALIDATED (35 U.S.C. § 101 - not patentable)

Acquired from Digital Networks North America, which filed in 2004.

System and method for automatically controlling a media receiver by instructing the media receiver to use a particular receiver connection and to play a selected media unit using one of a plurality of play modes according to characteristics of the media unit. Media units may be encoded using any of a variety of encoding formats. The media management system may interface with a media receiver to select media receiver connections in accordance with the media type of the media unit. The media management system may also interface with the media receiver to set media receiver settings for playing the selected media unit according to the media receiver settings selected for a play mode corresponding to the characteristics of the selected media unit.


Data entry via on-screen display (8,755,667) - 6/17/2014 - WITHDRAWN following claim construction

Acquired from Digital Networks North America, which filed in 2008

A recording playback device having a database of recordings with titles, automatically enters a title input mode upon receiving character input from a user while a recording is being played if the there is not title in the database for the recording. Playback of the recording is not interrupted in the title input mode. In the case of a DVD player, the on-screen display mode is used to display the characters entered by the user on the same.


Multi-channel video pump (6,473,441) - 10/29/2002 - WITHDRAWN following claim construction

Acquired from Escient, which filed in 1999

A system for streaming a plurality of video or other recorded signals from storage to receiving devices maintains each of the signal streams at their encoded bit rate. The bit rate of each stream is detected from the stored signals and a corresponding queue is set up in a network interface card for outputting data at the detected bit rate. A channel timing module in the signal streaming device contains pairs of counters, one pair for each stream. The primary counter in each pair is set to have a period slightly less than the period of the stored signal. A secondary counter in each pair is set to have a period that is larger than an integer multiple of the primary counter by an amount equal to the difference between the multiple periods of the primary counter and the same multiple of the stored signals. Every time either the primary or the secondary counter times out, a packet of data is sent to the corresponding queue in the network interface. As a result, the network interface is able to output isochronous signals with an average bit rate within one bit per second of desired bit rates between one megabit/second and 20 megabit/second and with a jitter of less than one millisecond.


Unification of multimedia devices (7,987,294) - 7/26/2011 - STILL IN PLAY (Claim construction recently issued; Sonos permitted to move for summary judgment of non-infringement.)

Acquired from Altec Lansing, which filed in 2007

Described herein are various methods and systems relating to the unification of media devices, and more specifically to the provision of wireless audio systems. In overview, two or more wireless speaker subsystem units substantially autonomously form a single wireless audio system having its own control interface. This control interface is used to apply operational changes across the wireless audio system, such as volume adjustment. That is, an operational change may be applied to the system as a whole, and this change is subsequently implemented by each of the individual wireless speaker subsystem units.


Sonos - asserted patents in lawsuit against D&M


System and method for synchronizing operations among a plurality of independently clocked digital data processing devices (9,195,258) - 11/24/2015 - D&M WILLFULLY INFRINGED

A system is described for maintaining synchrony of operations among a plurality of devices that have independent clocking arrangements. The system includes a task distribution device that distributes tasks to a synchrony group comprising a plurality of devices that are to perform the tasks distributed by the task distribution device in synchrony. The task distribution device distributes each task to the members of the synchrony group over a network. Each task is associated with a time stamp that indicates a time, relative to a clock maintained by the task distribution device, at which the members of the synchrony group are to execute the task. Each member of the synchrony group periodically obtains from the task distribution device an indication of the current time indicated by its clock, determines a time differential between the task distribution device's clock and its respective clock and determines therefrom a time at which, according to its respective clock, the time stamp indicates that it is to execute the task.


Method and apparatus for controlling multimedia players in a multi-zone system (7,571,014) - 8/4/2009 - D&M WILLFULLY INFRINGED

Techniques for controlling zone group and zone group characteristics such as audio volume in a multi-zone system are disclosed. The multi-zone system includes a number of multimedia players, each preferably located in a zone. A controller may control the operations of all of the zone players remotely from any one of the zones. Two or more zone players may be dynamically grouped as a zone group for synchronized operations. According to one aspect of the techniques, a zone group configuration can be managed, updated, modified via an interactive user interface provided in a controlling device. The zone group configuration may be saved in one of zone players. According to another aspect of the techniques, the audio volume control of a zone group can be performed individually or synchronously as a group.


Method and apparatus for adjusting volume levels in a multi-zone system (8,588,949) - 11/19/2013 - D&M WILLFULLY INFRINGED

A multimedia controller including a processor, the controller configured to: provide a user interface for a player group, wherein the player group includes a plurality of players in a local area network, and wherein each player is configured to playback a multimedia output from a multimedia source; accept an input to facilitate formation of the player group, indicating that at least two of the players in the local area network are to be included in the player group; for each of the plurality of players within the player group, accept an input to adjust a volume associated with the player, that causes the player to adjust its volume; and accept an input to adjust a volume associated with the player group, wherein the input to adjust the volume associated with the group causes the players in the player group to adjust their volumes



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  About the Author

Julie Jacobson is founding editor of CE Pro, the leading media brand for the home-technology channel. She has covered the smart-home industry since 1994, long before there was much of an Internet, let alone an Internet of things. Currently she studies, speaks, writes and rabble-rouses in the areas of home automation, security, networked A/V, wellness-related technology, biophilic design, and the business of home technology. Julie majored in Economics at the University of Michigan, spent a year abroad at Cambridge University, and earned an MBA from the University of Texas at Austin. She is a recipient of the annual CTA TechHome Leadership Award, and a CEDIA Fellows honoree. A washed-up Ultimate Frisbee player, Julie currently resides in San Antonio, Texas and sometimes St. Paul, Minn. Follow on Twitter: @juliejacobson Email Julie at julie.jacobson@emeraldexpo.com

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  Article Topics


Speakers · Loudspeakers · Wireless · Audio/Video · Distributed Audio · News · Products · D&M Holdings · Denon · Escient · HEOS · Lawsuit · Legal · All Topics
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Comments

Posted by dbendell on March 21, 2018

Any update? There was to be a March 5th court date.

Posted by txrdhog on March 2, 2018

This must be the reason Denon recently removed group volume control on the HEOS Drive. So when will Denon release a firmware update that provides group volume control for the thousands of HEOS Drive owners. Without this functionality it is like having a car radio that can only adjust one speaker volume at a time. It makes the HEOS system worthless in my opinion.

Posted by David Haddad on February 26, 2018

I would be very curious if D&M attorney’s had the foresight to put some Crestron programmers on the stand who could explain how room grouping and volume grouping were widely employed by even by small A/V firms a decade before Sonos “invented” them.

Posted by jonsmirl on February 26, 2018

If you are looking for prior art, here is public source code for a networked audio system using synchronized clocks that was written three years before the 258 patent was filed. Work began Jun 29, 2012.
https://github.com/thaytan/aurena

Posted by jhamill1 on February 26, 2018

Regardless of the final outcome, the one product line that will NOT be going into our customers’ homes is Sonos; they have been incredibly unfriendly to the custom market that built their original reputation.

Posted by jonsmirl on February 26, 2018

It is fine it Sonos wants to patent some squirrelly binary audio protocol that they are the only ones using.  It is not ok for Sonos to get a new patent containing claims on well known techniques. So the court will need to deconstruct this patent and remove all of the prior art that shouldn’t be in it. And then see if Denos infringes the very Sonos specific parts that are left.  The question here: is Denos skilled enough to bring inter partes review of the Sonos patents and present the needed prior art to invalidate all of the generic technology that should not be in these patents?

This is the core problem with software patents and why they should not be allowed. Before software patents existed you could only patent a specific implementation of an invention. For example you could patent a claw hammer, you could not patent the concept of “hammer”.  Software patents changed that by allowing you to patent algorithms. Patenting an algorithm is the equivalent of patenting the concept of “hammer”.  Once you get a patent to an algorithm you can control all uses of that algorithm including uses that never occurred to you.  This has resulted in things like software patents from Hayes modems being use to attack video codecs—something that hadn’t even been conceived of when Hayes modems were built.

Posted by Julie Jacobson on February 26, 2018

Netstreams had a patent on network-based audio-sync technology back in the day. I don’t understand it. I’ll just assume Sonos is doing it in a new and different way. I think also Sonos would be a sentimental favorite among juries.

Posted by jonsmirl on February 26, 2018

I glanced through the 258 patent. It does not mention a major IEEE standard (1588) addressing exactly the material being patented. That’s because the patent has intertwined audio processing and time synchronization which are two separate things.  If you divide this patent into the correct pieces—time synchronization (a well known core technology) with group notifications (another well know technique) layered on top, you can see that there is nothing new here.

Nothing new is being invented in multi-player home audio. LANs have been around a long time. The core implementation of all of this stuff occurred in the 1980s at Xerox Park, Microsoft and Novell.  These are just audio players hooked together on a LAN. That does not give you license to take every piece of LAN technology, add the work audio, and repatent it.

Posted by Julie Jacobson on February 26, 2018

You and me both, jonsmirl. I was especially baffled by the group volume control.

Posted by jonsmirl on February 26, 2018

There is an IEEE standard from 2008 addressing the area of the 258 patent. https://en.wikipedia.org/wiki/Precision_Time_Protocol
Protocols like this are commonly used on industrial productions line—like coordinating the robots you see working together in videos. Time synchronized audio using a similar protocol was implemented in Linux ALSA far before 2015.

As for 949, network group notification schemes have been around for over fifty years.  I hate these software patents that take a well know generic technique, group notifications, and then repatent it over and over with different packet contents. Group notification of volume,  Group notification of lighting control, Group notification of network login controllers, Group notification of robots, Group notification of traffic lights, Group notification of security cameras, etc…  This is not innovation and it should not be patentable.  Group notifications are such an old technology that it is part of the original Ethernet spec from 1980.

View all comments.

Posted by dbendell on February 26, 2018

In the meantime, Sonos has now destroyed all 3rd party drivers with 8.3 and has claimed it opened its API, which btw sucks, most features are gone for 3rd party. Sonos has become the NRA of audio streaming! Thoughts and Prayers!

Posted by jonsmirl on February 26, 2018

There is an IEEE standard from 2008 addressing the area of the 258 patent. https://en.wikipedia.org/wiki/Precision_Time_Protocol
Protocols like this are commonly used on industrial productions line—like coordinating the robots you see working together in videos. Time synchronized audio using a similar protocol was implemented in Linux ALSA far before 2015.

As for 949, network group notification schemes have been around for over fifty years.  I hate these software patents that take a well know generic technique, group notifications, and then repatent it over and over with different packet contents. Group notification of volume,  Group notification of lighting control, Group notification of network login controllers, Group notification of robots, Group notification of traffic lights, Group notification of security cameras, etc…  This is not innovation and it should not be patentable.  Group notifications are such an old technology that it is part of the original Ethernet spec from 1980.

Posted by Julie Jacobson on February 26, 2018

You and me both, jonsmirl. I was especially baffled by the group volume control.

Posted by jonsmirl on February 26, 2018

I glanced through the 258 patent. It does not mention a major IEEE standard (1588) addressing exactly the material being patented. That’s because the patent has intertwined audio processing and time synchronization which are two separate things.  If you divide this patent into the correct pieces—time synchronization (a well known core technology) with group notifications (another well know technique) layered on top, you can see that there is nothing new here.

Nothing new is being invented in multi-player home audio. LANs have been around a long time. The core implementation of all of this stuff occurred in the 1980s at Xerox Park, Microsoft and Novell.  These are just audio players hooked together on a LAN. That does not give you license to take every piece of LAN technology, add the work audio, and repatent it.

Posted by Julie Jacobson on February 26, 2018

Netstreams had a patent on network-based audio-sync technology back in the day. I don’t understand it. I’ll just assume Sonos is doing it in a new and different way. I think also Sonos would be a sentimental favorite among juries.

Posted by jonsmirl on February 26, 2018

It is fine it Sonos wants to patent some squirrelly binary audio protocol that they are the only ones using.  It is not ok for Sonos to get a new patent containing claims on well known techniques. So the court will need to deconstruct this patent and remove all of the prior art that shouldn’t be in it. And then see if Denos infringes the very Sonos specific parts that are left.  The question here: is Denos skilled enough to bring inter partes review of the Sonos patents and present the needed prior art to invalidate all of the generic technology that should not be in these patents?

This is the core problem with software patents and why they should not be allowed. Before software patents existed you could only patent a specific implementation of an invention. For example you could patent a claw hammer, you could not patent the concept of “hammer”.  Software patents changed that by allowing you to patent algorithms. Patenting an algorithm is the equivalent of patenting the concept of “hammer”.  Once you get a patent to an algorithm you can control all uses of that algorithm including uses that never occurred to you.  This has resulted in things like software patents from Hayes modems being use to attack video codecs—something that hadn’t even been conceived of when Hayes modems were built.

Posted by jhamill1 on February 26, 2018

Regardless of the final outcome, the one product line that will NOT be going into our customers’ homes is Sonos; they have been incredibly unfriendly to the custom market that built their original reputation.

Posted by jonsmirl on February 26, 2018

If you are looking for prior art, here is public source code for a networked audio system using synchronized clocks that was written three years before the 258 patent was filed. Work began Jun 29, 2012.
https://github.com/thaytan/aurena

Posted by David Haddad on February 26, 2018

I would be very curious if D&M attorney’s had the foresight to put some Crestron programmers on the stand who could explain how room grouping and volume grouping were widely employed by even by small A/V firms a decade before Sonos “invented” them.

Posted by txrdhog on March 2, 2018

This must be the reason Denon recently removed group volume control on the HEOS Drive. So when will Denon release a firmware update that provides group volume control for the thousands of HEOS Drive owners. Without this functionality it is like having a car radio that can only adjust one speaker volume at a time. It makes the HEOS system worthless in my opinion.

View all comments.