[Jack-Devel] Why can I only select 512 samples?

[Chris Caudle]

On Thu, February 22, 2018 1:02 pm, lowkeyoutlaw wrote:
> The actual driver was hard to come by, and is no longer supported. The
> driver on the site is actually ASIO4ALL, which works well, but ties up all
> audio system wide. I use an alternative ASIO from Image line/FL Studio
> called FL Studio ASIO, of course. It works a bit better than ASIO4ALL.
> Even if i use ASIO4ALL i get the same results.

The startup command for jackd.exe needs to know the correct driver name to
use when starting.  If you use the FL Studio ASIO driver, does it have FL
Studio ASIO as the driver name?
On the jack on windows page it shows the full command to use, typically
set as a shortcut.
You will be able to see the output better if you open a command prompt and
paste in the command there:
"C:\Program Files\Jack\jackd.exe" -R -S -d portaudio -d "ASIO::ASIO4ALL v2"

If you don't want to use ASIO4ALL then you need to change the string
"ASIO::ASIO4ALL v2" to whatever matches your actual driver name.
As shown on that same web page you can get the list of available drivers
with the l (lower case L) option:
"C:\Program Files\Jack\jackd.exe" -d portaudio -l

I suspect may show a different name for the FL Studio driver.

This is the full set of options for the portaudio backend.  You can give
them as extra arguments after the "-d portaudio" argument.  Don't put them
before, jackd will try to interpret them directly and probably print an
error about options not applying, make sure you put -d portaudio on the
command line, then any settings that need to be set for that backend
driver.

   PORTAUDIO BACKEND PARAMETERS
       -c --channel
              Maximum number of channels (default: all available hardware
channels)

       -i --channelin
              Maximum number of input channels (default: all available
hardware channels)

       -I --input-latency
              Extra input latency (frames) (default: 0)

       -o --channelout
              Maximum number of output channels (default: all available
hardware channels)

       -O --output-latency
              Extra output latency (frames) (default: 0)

       -C --capture
              Whether or not to capture (default: true)

       -P --playback
              Whether or not to playback (default: true)

       -D --duplex
              Capture and playback (default: true)

       -r --rate
              Sample rate (default: 48000)

       -p --period
              Frames per period (default: 1024). Must be a power of 2.

       -n --name
              Driver name (default: none)

       -z --dither
              Dithering mode (default: none)

> I'm going to try this again right now while I'm typing.
> -First, I opened the Jack Control Panel & set the buffer/latency to 1024

Not sure what you are calling the Jack Control Panel, but if it is what I
suspect it is the application you use to  make connections while jackd is
running, I have never heard that the Jack Control application can change
jackd startup parameters.

> -Second, I opened Jack PortAudio. I don't see any place on it to change
> any settings. It's just a command window.

If you followed the jack on windows page to setup the Jack PortAudio
shortcut then you set the command line in the shortcut, that is where you
change settings, by changing the command line executed by the shortcut.

> I just realised a couple days ago that this works without
> The Control Panel running.

Yes, the shortcut you setup for jackd will start jackd, the control panel
application is just so you can make connections between applications if
you have applications which are not jack native and so do not provide any
way inside the application to make connections.

I'm not sure about jackrouter, the application which provides ASIO
interfaces into the jack audio ports.  You may need to check
JackRouter.ini and make sure there is not a setting for buffer size there.
 I think JackRouter should get its buffer size from the jack server
though, so start by running jackd from a command shell so you can make
sure that buffer size is actually getting passed to jack.  I think it
should be something like this, possibly with the driver name changed to
match your FL Studio driver:

"C:\Program Files\Jack\jackd.exe" -R -S -d portaudio -d "ASIO::ASIO4ALL
v2" -p 1024

There is usually a -r argument for the sample rate (e.g. 44100, 48000,
96000).  According to the manual page it defaults to 48000, so if you
would prefer 44100 you should also add in -r 44100 after the other
arguments.
In fact, if you have source material at 44100 and you are forcing MPC
software to run at 48000 it may be doing sample rate conversion in the
background, which will probably be a bigger CPU drain than running at 512
instead of 1024 sample buffer size.

-- 
Chris Caudle