On 21/09/2015 10:34 AM, Bjorn Roche wrote:
I noticed that PortAudio's API allows one to open a duplex stream
with different stream parameters for each device. Does it actually
make sense to open an input device and an output device with...
* ...different sample rates?
PA certainly doesn't support this. You might have two devices open at
one time (one for input and one for output) and they might be running at
separate sample rates, but the stream itself will only have one sample
rate -- at least one device will be SR covered if necessary.
A full duplex PA stream has a single sample rate. There is only one
sample rate parameter to Pa_OpenStream().
* ...different latency / hardware buffer values?
Some host APIs support separate values for input and output. And yes, in
my experience you can get lowest full-duplex latency by tuning the
parameters separately for input and output.
PA probably only uses one of the two values in at least some situations
like this. In fact, on OS X (and possibly on other APIs),
It depends on the host API. e.g. an ASIO full duplex stream only has one
buffer size parameter.
the latency
parameter is often ignored completely anyway. (or at least it was when I
last looked at the code)
That is false. Phil and I did a lot of work a couple of years back to
fix the interpretation of latency parameters.
* ...different sample formats?
I don't think this is of much use to many people (anybody?). If it is, I
don't think the person who needs it would complain too much about a few
extra lines of conversion code, but maybe I'm wrong.
Agree. There is no particular benefit.
Ross.
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