[madbrain]

I have a small room with a TV and ceiling speakers. The speakers are powered by an AVR located in another room. There is a Chromecast audio attached to that AVR. It is wired to the network rather than using Wifi, so latency should be OK.

The TV is 9 years old, but still quite good - 60" Sharp Aquos 3D TV. But the audio really sucks, as most TV speakers do.

I have a Raspberry Pi 3 attached to an Ubiquiti NanoHD wave 2 wireless AP through a Trendnet Gigabit NIC.
It plays Blu-ray ISO and 3D Bluray ISO from my NAS quite well. Except for the audio part.

Is there any chance one could use Kodi on the Pi3 to stream the audio to the Chromecast audio instead of HDMI, while still streaming the video over HDMI ?

[Klojum]

Is there any chance one could use Kodi on the Pi3 to stream the audio to the Chromecast audio instead of HDMI, while still streaming the video over HDMI ?

Not likely. Kodi is all open-source, and Chromecast is proprietary/closed software from Google.
Those two types do not mix will in ourview. Thus, Kodi has no support for Chromecast, for audio or video.

[madbrain]

Is there any chance one could use Kodi on the Pi3 to stream the audio to the Chromecast audio instead of HDMI, while still streaming the video over HDMI ?

Not likely. Kodi is all open-source, and Chromecast is proprietary/closed software from Google.
Those two types do not mix will in ourview. Thus, Kodi has no support for Chromecast, for audio or video.

Yes, I'm aware it is closed-source. Are there other streaming devices that would work for my use case ? Say, if I had a Raspberry Pi with PiCast or equivalent, would there be a chance for Kodi to use it as an audio device when playing videos ? I realize there would likely be some audio/video sync issues, but those could be hopefully adjusted manually with some delay parameter.

[madbrain]

Is there any chance one could use Kodi on the Pi3 to stream the audio to the Chromecast audio instead of HDMI, while still streaming the video over HDMI ?

Not likely. Kodi is all open-source, and Chromecast is proprietary/closed software from Google.
Those two types do not mix will in ourview. Thus, Kodi has no support for Chromecast, for audio or video.

Klojum - didn't see a followup to my last response.

I see that Kodi already supports UPnP/DLNA players. There is even software I can run (on a Pi, or other device) that will create a DLNA server and pipe audio to my Chromecast audio.

My use case is one where the audio device and video device aren't one and the same.
In my case, I want the video to go for HDMI, and the audio over to the DLNA player.
It's possible others might have the opposite need of mine, where the local device running Kodi sends the audio, but the video stream needs to be sent to a remote device.
I understand this may not be a very common use case, but for those with multi-room audio / in-wall/ceiling speakers, it is likely not that uncommon. I have over 50 speakers in my house, but there isn't an amplifier for speakers in every room. Only 2 rooms have amps that feed most of the speakers. All those amps have audio streamers attached - in my case, CCAs, but they really could be Rpi with DLNA servers instead, or other open-devices.

[RockerC]

Is there any chance one could use Kodi on the Pi3 to stream the audio to the Chromecast audio instead of HDMI, while still streaming the video over HDMI ?

Not likely. Kodi is all open-source, and Chromecast is proprietary/closed software from Google.
Those two types do not mix will in ourview. Thus, Kodi has no support for Chromecast, for audio or video.

FYI, Chromecast is closed source but the Google Cast protocols have been reversed engineered and then that reverse-engineering effort that been released as open-source libraries, just as an example check out PyChromecast:

https://github.com/home-assistant-libs/pychromecast

PyChromecast is has been actively developed for over 5-years as a popular feature in the Google Cast integration for Home Assistant (it was even developed by its founder): 

https://www.home-assistant.io/integrations/cast/

PyChromecast is only one of a few reverse-engineered libraries for Google Cast protocols but it probably the most mature. stable, and best maintained:

https://pypi.org/project/PyChromecast/#history

Many if not most protocols that Kodi do supports today are or have at some point been proprietary/closed source but have been reversed engineered and then that effort has been released as independent open-source code libraires.

[Klojum]

Sure, all we need now is to have someone port it into Kodi sourcecode. Are there any volunteers?