Multi-Room Music Sync

The problem is the clocks in the separate Pi’s (or any audio playback devices) are not synchronised.
Clock accuracy (from the crystal oscillator) means they may drift by about half a second every hour.

If you are standing in the doorway between two rooms playing the same file that audio offset will be very disconcerting.

Devices like sonos have a PLL adjustment on their clocks to force the devices to be synchronised to <1ms to allow multi-room audio to work well. They are expensive though.

Technically the Pi can do this from a hardware point of view, but as there is no standard API for achieving this across different platforms, upstream kodi will never support this.

You can get a similar effect from resampling the audio by very small factors (e.g. 0.01%) but that would probably upset the audiophiles. But in theory that scheme could be handled in a platform agnostic way and could be implemented by upstream kodi.

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