Synchronized Wireless Audio/Video using Wi-Fi
22/10/2019

Wi-Fi expected to replace proprietary wireless audio technologies to enable synchronized wireless Audio/Video streaming inside the home.

Figure 3 visualizes the major CE use-cases for synchronized wireless audio/video.  Accurate timing synchronization using Wi-Fi enables the transition – step-by-step dealing with the increasing need for higher accuracy – from traditional asynchronous wireless audio applications to synchronized wireless cinema-mode audio/video applications.

Figure 3: Increasing accuracy for wireless timing synchronization enables new AV use-cases 

Asynchronous Wireless Audio is the traditional wireless CE-use-case, where audio can be simultaneously streamed to different wireless speakers in the home, but no accurate synchronization is enforced.  This basic use-case can already be fulfilled with plain-vanilla Wi-Fi (or alternative technologies) and will not be discussed further. 

The major differences between the synchronous use-cases are the following:

  • Synchronous Wireless Party-Mode Audio: In this use-case, all the wireless speakers (or more generally, all the wireless sinks) in a synchronized group of speakers play the same audio in sync.   Most often, the different speakers will be placed in multiple rooms, and accordingly this use-cases is sometimes called “synchronous multi-room audio”.  However, the latter terminology is technically incorrect, as the audio sinks can all be placed in the same room as well.  Alternative names for this use-case include “synchronous same-channel audio” and “wireless broadcast audio”.

  • Synchronous Wireless Cinema-Mode Audio: In this use-case, each wireless audio sink in a synchronized group of speakers plays one (or more) dedicated audio channels out of an audio multiplex containing multiple channel(s). In its most basic form, the left and right channels of a stereo track are played by 2 separate wireless speakers. In more advanced channel configurations – for example, 5.1, 7.1, 7.1.4 or even more complex surround sound configurations – a large number of wireless speakers can be involved, each playing a single channel of the audio multiplex (e.g. Front Left, Rear Left, …) or a specific combination of audio channels (e.g. Front Left + Front Height + Sub).

    Because all of the wireless speakers are typically located in the same room, this use-case is sometimes referred to as “synchronous same-room audio”.  Alternative names for this use-cases are “wireless surround-sound audio” and “wireless home theater audio”.

  • Synchronous Wireless Cinema-Mode Audio/VideoThis use-case is similar to the previous one, with the major exception that one (or more) wireless video channels are included as well.  In other words, this use-case involves video sinks in addition to audio sinks.  For lip-sync purposes, the audio and video channels need to be synchronized properly to ensure the best possible entertainment experience for the user.


An essential feature for the CE use-cases is obviously the inter-device time synchronization – i.e. audio/video sinks in the same playback session need to be accurately synchronized to get the best possible user experience.  Figure 4 illustrates an example where multiple groups of synchronized audio and video sinks coexist next to each other. 

  

Figure 4: Different audio sinks can be grouped together into sets of synchronized audio sinks to enable the synchronous CE Use-cases


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