More than two audio channels thru audio hat?

#1

This probably should be posted elsewhere (Kodi forum?) but I thought I might be a more intelligent answer here.
I really like the HifiBerry hats for the raspberry pi. Most hats are just stereo DACs (two channels of line out, but they also have a stereo amplifier hat (25 watts or so.)
The audio quality is great, and they’re cheap and compact.
I requested that they build an AV 3.1 or 5.1 hat that would work with Kodi. I was told that linux/Kodi doesn’t support more than two audio channels except thru HDMI.
Is this true?
It seems like an unfortunate restriction.
If not true, can someone point me to any documentation that I can pass back to HifiBerry.
In case it’s not obvious, this would allow a player (OSMC or other) to be able to directly drive speakers, without needing an HDMI receiver.

#2

No. You can get up to 5.1 through S/PDIF. No reason why their Digi+ HAT should not work.

#3

It seems to me the use case for such a product would be too niche to actually turn into a commercial offering whether possible or not.

#4

Here is the reply from HifiBerry:

Believe me that we know the Raspberry Pi audio hardware a bit better than at least some of the OSMC developers. The audio interface for onboard sound is only 2-channel.
One could do crazy hacks around this (like multiplexing multiple channels into one), but this wouldn’t be something that we would want to sell as it won’t work stable and wouldn’t provide the sound quality that we want to offer. Our USB interface could drive 8 channels, but this also would be a relatively expensive solution. Not sure if we will go this way in the future.

Any feedback on who’s correct? I’m assuming that Kodi can drive the i2s bus with a standard multi-channel sound format, so I’m not sure what he means by “audio interface for onboard sound is only 2-channel”.

#5

Your asking about more than two channel LPCM, HifiBerry is saying there is a hardware limitation of two channel LPCM. I would have no reason to doubt what they are saying.

Grahamh was answering the question about “Linux/Kodi supporting more than two audio channels except thru HDMI” which was an answer not constrained to hardware or the transfer medium. He was telling you that their Digi+ HAT can output 6 channel audio through S/PDIF. The distinction being that the signal from S/PDIF is a compressed bitstream and not LPCM. He quoted a specific piece of your OP, and he was responding only to that.

These statements are not conflicting with each other. You simply were not getting the full context of the statements.

If you really want 6 channel LPCM output from a Raspberry Pi to to a D/A converter then you would have to go to a device that plugs into the HDMI port and breaks the audio out from there. These devices exist, but it seem that you would have to have a very specific need for such a device to want to go that route.

#6

I don’t know either. On their website for the DIGI+ they say:

Important note: While the hardware is able to output DTS/Dolby Digital, software has to be adapted to support this. We will support the developers to implement this. Unfortunately we can’t guarantee that this feature will work with a specific software. Please ask the developers of the software if this is supported.

I can’t see any structural reason why Kodi could not get DTS or DD and feed it to their board. As far as RPi is concerned, it would be 2 channels at the hardware level.

However, it seems you are really looking for multi-channel LPCM output. @darwindesign’s suggestion of an HDMI audio break-out device would do it, or a USB soundcard. But neither would provide any amplification.

#7

Just to be clear, what I was hoping for was a 5.1 (6 DACs) or 3.1 (4 DACs) hat for a raspberry pi, that would automatically work with KODI to play DTS multichannel formats. It looks like there is a standard format for encoding this over the standard 2 channel hardware interface.
Powered speakers are cheap and good, so just line out is fine. KODI seems to have plenty good enough decoding built in.

#8

It is not going to happen as a hat. If you wanted to do it with powered speakers or DIY class D amps then you would have to use a product like this…


…but your probably going to have some issues with volume control to sort out. You would be better off IMO picking up a cheap AVR second hand if there was a budget constraint.

#9

I was planning to use powered speakers, so I just need a hat with 4 DACs (i.e. 4x line out) as compared to the current HifiBerry hat with 2 DACs and 2x line out.
KODI can do volume control (or the hat.)
It’s not a budget issue but space/mounting. I have plenty of extra AVRs but they don’t mount well on walls. With KODI on an RPI+Hat, plus 3 or 4 powered speakers, I’d have a nice 3.1 unit for, say, an exercise room.

#10

Most people find using a soundbar in that situation a more sensible approach.

#11

I’m currently using a soundbar. I was hoping for a simple solution with better sound quality.
There are 4K hdmi splitters on Amazon which should work - thanks for the link.
I really like the HifiBerry hats for ease of use and sound quality, and thought a 5.1 version (for around $100) would be great. Sounds like nobody else is interested, including HifiBerry.

#12

It doesn’t make sense for them. They would have to encode 4/6 channels to DTS (say) to squeeze them through RPi’s two internal channels, then de-code them in the HAT and the result would be poorer quality because of the compression.