Re: [Jack-Devel] JACK2 for Android newly released!

2014. 1. 28. ¿ÀÀü 12:59¿¡ "Christian Schoenebeck" <[hidden]>ŽÔÀÌ
ÀÛŒº:
>
> On Saturday 25 January 2014 14:55:11 ±èÁ€¿¬ wrote:
> > > First, the framework only supported I/O via built-in audio devices. No
> > > USB. This means audio quality is compromised by their audio hardware.
> > > Importantly, they are restricted to 48k/16 bit.
> >
> > Yes, it is true, but most of things are platform dependent. Not a jack
> > domain.
>
> What do you mean with "platform dependent"? External USB audio devices
usually
> support the "USB audio class" standard protocol nowadays. Support for such
> devices is provided by a standard Linux kernel module which is platform
> independent.
Yes. android officially support USB Audio by framework level.
But, how to JACK access and use /dev/usb/... as audio device using jack
driver?
I have no background about that.
Are there any bridge between usb~alsa?

>
> > I think these XRUNS related cpufreq on demand governor when a jack
client
> > runs during low CPU frequency mode in mobile device. Please refer:
> >
http://bamboopuppy.com/android-cpu-frequency-using-cpufreq-ondemand-governo
> > r/ As I know, there were already discussion in here, so I found Robin's
> > jackfreqd, How do you think for solution?
> > http://rg42.org/oss/jackfreqd/start
>
> Yes, CPU scaling (CPUFreq) is one of the major reasons for xruns. You
could
> first try whether this is the case by:
>
>         cpufreq-set -r -g performance
>
> to find out whether that is sufficient to solve the xruns. That would set
the
> CPU cores to maximum performance. If that looks well, you could then go
ahead
> with a production solution like i.e. jackfreqd or something based on that
idea
> to both save power whenever possible and not having xruns in audio
> performances.
Ok. Thanks.

>
> > >> > What about low latency/RT stabilty, have you tested running JACK2
with
> > >> > low latency period settings (i.e. <= 5ms) on Android? Does it run
> > >> > quite stable without xruns?
> > >>
> > >> Well, it is hard to say, latency depends on platform limitation or hw
> > >> spec. for example, android's fast mixer introduces 10ms of latency.
> > >> http://source.android.com/devices/latency_design.html
> > >>
> > >> Generally, mobile devices do control power consumption much sensitive
> > >> than PC, of course this limitation may possible occur XRUNS in some
> > >> scenarios.
> > >> We always think how to improve performance better, *** so I need
> > >> expert's advice here. ***
> > >> But, modern mobile devices increase number of cores(quad-core or
> > >> more...), so I guess JACK2 works better performance along with number
> > >> of cores. Of course, it works stable if allows reasonable clock-speed
> > >> and cores.
>
> I don't know what kind of hardware components you are using exactly, but I
> somehow doubt that latency issues are caused by your hardware. iOS devices
> deliver rock solid low latency from day one (for more than 6 years now).
And
> there are various other ARM based hardware on the market which also
deliver
> reliable low latency if being equipped with the right OS & co.
>
> Are you running a hypervisor kernel like OKL4 on lowest level and
> Android/Linux on top of it? Or is the Android/Linux kernel running
directly on
> the ARM CPU?
I have no idea about hypervisor or something.

>
> Best regards,
> Christian Schoenebeck

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