I've read that at the moment the Pi 4 isn't great at streaming 4K videos, but that's bound to evolve. Small, cheap, fanless, 4K video. I don't even own a television but I can tell you that there will be great demand for a 5.1 solution.
I'm sure I didn't need to tell you that.
Cheers,
KO
FWIW, I'll want cases for the Pi 4 with HiFiBerry cards now. Just being Captain Obvious here...
As long as the GPIO audio hasn't changed (and I do not expect this), there will be no 6 channel sound card as the GPIO sound interface is limited to 2 channels.
The first cases will be available in a few weeks.
Best regards,
Daniel
Daniel, if i understand it right, it is not possible to use 5.1 PCM audio for output or input (Digi+ IO) due to this limitation?
I think, this will answer my question (https://support.hifiberry.com/hc/en-us/community/posts/360006209477) too.
The Digi+ is also just a 2-channel sound card (this is not just a limitation of the Raspberry Pi, but SPDIF itself is a stereo interface and wasn't designed for multichannel audio). You can use 2 stereo channels to encode 5.1 sound in Dolby Digital or DTS. However, for the Digi+, this still looks like a stereo data stream. It doesn't know anything about the stuff that's encoded in this data.
Best regards,
Daniel
ok, thanks for that clarification; i really believed until now that is possible to stream 5.1 pcm over spdif...
Thanks for the update Daniel! In general I'm really excited by the Pi 4 because it addresses the things I found really limited it as it now has up to 4 GB RAM, 1 Gb ethernet and USB3. It's a really viable product for a lot of things (e.g. NAS) that it wasn't.
It's a pity that the GPIO is limited to a stereo interface. I'm not even wising for my own needs. Personally I use the Pi + HiFiBerry for multiroom audio and my entire system (10 clients, two servers) is stereo. I just looked at those specs and thought it would make an incredible media center for the home theater crowd.
Thanks for your incredible products. Yes I have bought 10 different HifiBerry cards.
KO
The only way (currently) to get 5.1 out from the Pi is via HDMI. This works also with PCM streams and with all Pis (from 1 to 4).
For I^2S, I guess one could hack something up. It is true that the interface only supports stereo, *but* it doesn't really care what is transmitted. So with some Linux driver and matching hardware one could e.g. configure i2s to 192kHz (the highest supported by the Pi, AFAIK), then transmit 48kHz 5.1 sound e.g. like so: 2 sync words (to give the HW a chance to find the start), FL, FR, RL, RR, Center, LFE.
You used the right word: "hack" ;-)
Sure, you could put some 48kHz data into 192kHz and re-extract it. However, we feel the effort to create something like this that runs stable and the limitation to 48kHz isn't really something that makes sense for us. If somebody want's to experiment with this, the DAC+ DSP or Beocreate 4CA could be a good platform as the DSP could be used to extract data multiple channels. We're not planning something like this in the near future. I would only recommend this to someone who has really a lot of knowledge about Linux drivers and the internals of the ALSA sound subsystem.
Yes, it would be a hack. But I don't think there'd be a problem with stability. One would need to expose 24 bits max resolution to alsa, to be able to have a unique (32 bit) sync word.
The 48kHz limitation would be there, sure. But I don't know of any movies (the main (only?) source for surround) which come with a higher sampling rate.
Also, you'd only use this mode when requested. The card could still offer standard stereo up to 192 kHz (e.g. two alsa sinks, one stereo up to 192kHz, one 5.1 up to 48 kHz).
Btw. a similar hack is used for DTS, AC3 etc. over SPDIF in production. ;)