The final boss

[VoidXH]

This is it. The best way to easily add real-time Atmos decoding to media players. No DirectShow, no plugins, easy to integrate. Create a named pipe host that runs in the background, optionally starting with the PC, that takes any incoming data, and render it as PCM with the current Cavern setup. Make a reference client implementation in C++, and start contributing it to some open source players.

[VoidXH]

Beta implementation done in 20a1948. Protocol finalized, media players could theoretically start implementing it. Need to fix a single bug marked with TODO and add full file processing solution to reference implementation. Documentation is also WIP.

[VoidXH]

Bugs fixed and language handling added in 0c281c8. Remains:

• The window would look nice with channel meters and a green/yellow/red indicator if the server is running, waiting for playback, or not running.
• Documentation, containing all protocol bytes. It shall include that sending a single 0 byte triggers retrieving all rendered frames.
• Reference client shall actively wait for all rendered frames.

[VoidXH]

CavernPipe is finalized and documented in 9f8ddc8. To close this issue, implementation in any player is required, then I release CavernPipe bundled with that player on the website, with a single installer, that installs CavernPipe to be automatically launched with Windows.

[ThreeDeeJay]

So this requires the player to be modified? Or could we eventually just passthrough Atmos via a virtual audio device (or loopback a real S-PDIF device) into Cavern? Perhaps @dechamps would know if/how that'd be possible. 👀

sView would be a great open source player to implement this in (unless it could eventually decode and play LAF or perhaps even Atmos natively), though I think PotPlayer is hands down the best free player on Windows feature-wise, especially for 3D content, though it's closed-source. 🤔

[dechamps]

could we eventually just passthrough Atmos via a virtual audio device (or loopback a real S-PDIF device) into Cavern?

This would require one to write a Windows virtual audio driver which exposes Atmos bitstreaming capability and then hands the stream back to Cavern in userspace. I think that's technically doable, but writing Windows audio drivers is definitely not for the faint of heart. Modifying players would be much easier.

[EaryChow]

This would require one to write a Windows virtual audio driver which exposes Atmos bitstreaming capability and then hands the stream back to Cavern in userspace.

There are freely available solutions like Voicemeeter, VB Cable, VB Matrix, etc. Though these are all from VB audio, but they are free to use. Voicemeeter and VB Matrix seems to only support 8 channel audio at most, but VB Cable has 16 channel audio support. I can imagine a chain where we take in bitstream into Voicemeeter's virtual microphone, and then Cavern picks up the mic signal and decode, output to to VB Cable, and then I can use VB Cable to send the decoded PCM signals to the binaural renderer APL Virtuoso that I have been using. Cavern only needs to be able to pick up a microphone signal since there are third party solutions.

[dechamps]

There are freely available solutions like Voicemeeter, VB Cable, VB Matrix, etc.

I would be very surprised if any of these advertise Atmos bitstreaming support on their virtual audio devices. I'd expect you'd need to ask for that as a new feature. I don't think players will send a bitstream if the Windows audio endpoint device doesn't advertise support for it.

[EaryChow]

I would be very surprised if any of these advertise Atmos bitstreaming support on their virtual audio devices. I'd expect you'd need to ask for that as a new feature.

Good point, just did some search, it seems in some forum posts they said they only support PCM streams.

But having a virtual input option in Cavern is still a nice move to prepare for the potential future. Cavern doesn't have to ship a virtual cable with it, having a slot is better than nothing, I guess. I think it would also make it easier for making the feature request to the cables.

[VoidXH]

One thing to note regarding virtual audio devices, is how bitstreams are actually handled over SPDIF or HDMI. While there is metadata over HDMI regarding the codec, it's still SPDIF-compatible: set the stereo sample rate to 192 kHz, and just push the AC-3 bytes through. Cavern can definitely pick this up and play it back.

However, as regular bitstreams, this will make you lose volume control in-player, will add a detection delay, always has to run a microphone, which will scare privacy-concerned users, etc. CavernPipe has none of these issues.

[VoidXH]

Current status:

• KODI: mentioned, they like the idea, but the subsystem is abandoned, written email, no reply.
• MPC-HC: mentioned, not applicable as it's passing the packets to LAV.
• LAV Filters: mentioned, no reply.

These would have been the best options as market leaders, but maybe I'll fork Kodi when I have the time again for Cavern.