My specific application (speaker crossover) is to take a digital stereo signal from a Toslink source, then apply software filtering in the Pi to output to two 4-way speakers (each speaker has a Tweeter, Midrange, Woofer and Subwoofer, each powered by its own amp).
Your "multiple Pi" architecture can do this but would be hardware heavy. How big an issue is channel swapping?
The channel swapping issue has been reported solved when using
jackd, check here :
https://github.com/Audio-Injector/Octo/issues/1#issuecomment-455135061
I also have a software method for determining input channel alignment in the process method here :
https://github.com/flatmax/gtkiostream/blob/master/test/ALSAFullDuplexMinScan.C#L40
I would like to hear from people about whether the input channel alignment method can help to align output channels. I assume it will, however haven't spent the time testing and observing.
Matt
Peter
On Fri, 24 Jul 2020, at 09:06, Matt via People wrote:
There are a few different approaches to multichannel output.
One approach is the Octo sound card with 8 outputs and 6 inputs. The inputs can be time aligned in software to ensure that no channel swapping occurs. It is assume this approach can also then be used to ensure the outputs don't have channel swapping either. Some people have reported methods to ensure there is no output channel swapping based on using a jackd subsystem at startup and never stopping it.
Another approach is to use one Pi as the I2S bus owner - doing all of the clocking. Then you can have one Pi per TDM slot. For example, the one sound card can dump I2S input which all Pi can read. Each Pi can then do the processing and do stereo output.
Matt
On 24/7/20 10:49 am, Peter Heydenrych via People wrote:
Not really...I am trying to build a more flexible version of the obsolete MiniDSP OpenDRC-DA8, but with optical input, balanced output and more flexible processor. With a Pi 4 and Ultra 2 I am almost there...
On Fri, 24 Jul 2020, at 08:13, Matt via People wrote:
Perhaps we should do a digital input + analogue output board.
To do digital input properly it needs a software interface. The board is meant to tell the software what the incoming sample rate is.
Do you have any ideas around that ?
Matt
On 24/7/20 9:20 am, Peter Heydenrych via People wrote:
I'd love to use the 8 balanced outputs of the Ultra 2 - just need an optical input instead of the analogs...
Peter
On Fri, 24 Jul 2020, at 07:18, Matt via People wrote:
To add a toslink input, it would need to operate the I2S clocks - that would require a different hardware topology to the current devices.
I think we should do a new product based on this concept. Would you be using outputs ? If so what type of output would you want ?
Matt
On 24/7/20 8:40 am, Peter Heydenrych via People wrote:
Thanks for the quick reply, Matt. Would it be possible to add another device to bring in a Toslink signal? Do you know of anything that would be compatible?
Peter
On Fri, 24 Jul 2020, at 06:37, Matt via People wrote:
Hey Peter,
I would love to be able to do this, however that tollink connector is driven by the codec. They do the I2S to S/PDIF conversion on chip. S/PDIF receiving is more complex then sending because we also need to interrupt the operating system to notify it of a sample rate change.
Perhaps it is a good idea to do a future project with the S/PDIF injection capability.
Matt
On 24/7/20 8:27 am, Peter Heydenrych via People wrote:
Hi all,
I have just ordered an Ultra 2 but now see the Toslink option is an output.
Is there any possible way to add a Toslink input to a Pi + Ultra 2 system?
I'd prefer it if the Toslink output could be converted to an input, but adding another module to the system would be acceptable.
Thanks,
Peter
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