[Jack-Devel] Cannot combine audio devices with more than 64 channels

[Thomas Brand]

On Tue, January 24, 2017 16:27, Thomas Brand wrote:
> On Tue, January 24, 2017 09:22, Ralf Mardorf wrote:
>
>> On Tue, 24 Jan 2017 07:41:50 +0000, j at jrigg.co.uk wrote:
>>
>>
>>> On Mon, Jan 23, 2017 at 05:35:57PM +0000, Fons Adriaensen wrote:
>>>
>>>
>>>> With the official zita-ajbridge you can disable resampling.
>>>>
>>>>
>>>
>>> Good to know.
>>>
>>>
>>
>> Could this be used without word clock, by using a digital interface to
>> sync, e.g. S/PDIF? If so, assuming two identical cards would be used,
>> would sync be hat good, that each combination of IOs, e.g. a channel
>> from one card for the left and of the other card for the right channel
>> of a stereo signal, wouldn't cause phasing issues?
>>
> yes i think that works pretty good (drawing from earlier experiments).
> Using S/PDIF just for sync is a cheap alternative to a "real" wordclock.
> One of both interfaces will be slaved to the other and then both should
> run the same cycle at the same time (so theoretically no phasing issues).
> You just have to manage to shove forth and back the sample data from/to
> interface at good enough rate which isn't a particular problem on localhost
> using UDP like zita does. If there is no resampling involved, this can
> work for many many channels without hitting the CPU too much.
>
> Greetings
> Thomas
>
Even if the interfaces are synchronized with S/PDIF, there will be some
cycles (hopefully a static number) needed to shove data forth and back.
This needs to be considered to effectively get synchronous behaviour for
input or output to both interfaces.