Hi folks,
Can the DSP in DAC+DSP be used to map multichannel input from optical in to optical (for fronts for eg) and to line out (for rears for example)?
map center to front left + right, lfe to front+read, then output Front channels on optical as stereo PCM and Rears on line out.
This is until you folks release the multi channel DSP board.
Thanks!
The Pi's audio interface is limited to 2 channels. That's probably the main reason, we haven't worked on any multichannel hardware.
But simple things like center = l+r and lef=l+r filtered are possible with the "expert" settings in the HiFiBerryOS filter designer.
i am working on regular raspberry os as i use the os for other things as well.
what does it mean that pi audio interface is limited to 2 channels?
are you refering to i2s gpio pins, a software limitation or some other limitation?
also, my question was more around what can i do with the dac+dsp board.
as far as i understand sound will be processed in the board dsp exclusively, the pi will not even see the sound in any way, right?
Yes, I refer to the hardware I2S interface that can only handle 2 channels.
When using the Pi for audio playback is sent to the DSP via this interface. While the Pi isn't involved in the DSP processing, it sends the audio data to the DSP and therefore is limited to 2 channels.
If you're referring to Dolby Digital or DTS over TOSLink, this isn't supported at all. It would not only require a different DSP, but also a license that wouldn't be available for DIY hardware.
I was in fact thinking ab receiving (compressed) 5.1 over toslink to the dsp and output directly from the dac+dsp board w/o having the sound get to pi.
i assume receiving (compressed) 5.1 on optical involves something more than PCM, dolby digital (plus) or DTS?
I think outputting multiple channels could be solved using USB dacs or interfaces; i've read a few stories of people doing it, but it seems receiving multichannel is not straightforward.
Can you point me to more info on the licensing topic?
There are public informations on the licensing from both Dolby and DTS.
But multichannel audio is being passed of the stereo only toslink already.
Can this passthrough dac+dsp to the main rpi cpu where dolby like things can be decoded?
No, that's not possible. The TOSLink input can only handle PCM audio.
Thanks for the clarification.
Just experienced compressed audio comming in to the board and it's just noise.
I assume it doesn't get decoded and it's interpreted in the wrong way.
I guess it all boils down to the i/o of rpi which is limitted for this use case, except for the usb ports, where you can i/o multichannel.
i guess hdmi (e)arc is the way to do; i know of some SBCs that do hdmi earc and maybe rpi 5 will also do it.
I think i should be able to output multiple channels if i play back form rpi itself, using multiple output devices at the same time with camilla dsp or smth.