linuxaudio.org

--f46d040168f1b3512804cf937a0b

Content-Type: text/plain; charset=ISO-8859-1
Hi !!!
   I am using a jack_delay to measure the Fast Track Pro latency, but

something strange happens...It doesn't matter what configuration I am doing

on Jack that the latency value always is increase during the time... like

the result below:
ladeira@debian:~/Downloads/jack_delay$ ./jack_delay -E -O system:playback_1

-I system:capture_1

???     412.673 frames    8.597 ms

???     412.671 frames    8.597 ms

???     412.671 frames    8.597 ms

???     413.487 frames    8.614 ms

???     413.657 frames    8.618 ms

???     413.670 frames    8.618 ms

???     413.671 frames    8.618 ms

???     413.671 frames    8.618 ms

???     413.671 frames    8.618 ms

???     414.455 frames    8.634 ms

???     414.654 frames    8.639 ms

???     414.670 frames    8.639 ms
What am I doing wrong??
2012/11/26 Guillaume Pellerin 
> On 23/11/2012 20:01, rodrigo@angoera.com.br wrote:

quoted text
> >

> > Hi !!!!!

> >

> >   The Fast Track Pro is USB 1.0, the max bandwidth is 12Mb/s. The

> TUSB3200 has

> > the isochronous USB transfer mode, that can occupy about 90% of the USB

> > bandwidth... Using 4 channel (2 IN and 2 OUT) with right and left, and

> 24 bits

> > (3 bytes each, in total 4(channel) * 2(left,right) * 3(data) = 24 bytes

> ) The

> > max bandwidth  that could communicate is about 12Mbits/s = 1.5 Mbytes/s

> | 1.5

> > Mbytes/s * 0.9 = 1.2 MBytes/s --> 1.2MBytes/s / 24 bytes = 50Khz ... So

> the

> > maximum USB 1.0 with 24 bits is 4 chanel in 48KHz...

> >

>

> You're absolutely right, the 24 bits 4 channels mode would be only

> accessible in

> 48 kHz samplerate.

>

> >   I would like to know how it works the interface between USB AUDIO

> CLASS device

> > driver and the USB-AUDIO Alsa Device driver. And how does the isochronous

> > comunication works inside the kernel? Because I am using an RT Kernel

> and I

> > would like to set with the high priority this communication.

> >

>

> I don't really know how does the isochronous, but applying usual RT

> security

> audio rules seems sufficient to get high priority access and then very low

> latency (got 3 ms here with few audio realtime processes..).

>

> Further info here:

>

> http://joegiampaoli.blogspot.fr/2011/06/m-audio-fast-track-pro-for-debia...

>

> G

>

--f46d040168f1b3512804cf937a0b

Content-Type: text/html; charset=ISO-8859-1

Content-Transfer-Encoding: quoted-printable
Hi !!!=A0 =A0I am using a jack_delay to=A0measure=A0the=

 Fast Track Pro latency, but something strange happens...It doesn't mat=

ter what configuration I am doing on Jack that the latency value always is =

increase during the time... like the result below:

ladeira@debian:~/Downloads/jack_delay$ ./jack_delay -E =

-O system:playback_1 -I system:capture_1??? =A0 =A0 412.673 fram=

es =A0 =A08.597 ms??? =A0 =A0 412.671 frames =A0 =A08.597 ms??? =A0 =A0 412.671 frames =A0 =A08.597 ms

??? =A0 =A0 413.487 frames =A0 =A08.614 ms??? =A0 =A0 413.6=

57 frames =A0 =A08.618 ms??? =A0 =A0 413.670 frames =A0 =A08.618=

 ms??? =A0 =A0 413.671 frames =A0 =A08.618 ms??? =A0 =

=A0 413.671 frames =A0 =A08.618 ms

??? =A0 =A0 413.671 frames =A0 =A08.618 ms??? =A0 =A0 414.4=

55 frames =A0 =A08.634 ms??? =A0 =A0 414.654 frames =A0 =A08.639=

 ms??? =A0 =A0 414.670 frames =A0 =A08.639 msWhat am I doing wrong??=A0

2012/11/26 Guillaume Pellerin <lists@paris=

son.com>

On 23/11/2012 20:01, rodrigo@ango=

era.com.br wrote:

quoted text
>

> Hi !!!!!

>

> =A0 The Fast Track Pro is USB 1.0, the max bandwidth is 12Mb/s. The TU=

SB3200 has

quoted text
> the isochronous USB transfer mode, that can occupy about 90% of the US=

B

quoted text
> bandwidth... Using 4 channel (2 IN and 2 OUT) with right and left, and=

 24 bits

quoted text
> (3 bytes each, in total 4(channel) * 2(left,right) * 3(data) =3D 24 by=

tes ) The

quoted text
> max bandwidth =A0that could communicate is about 12Mbits/s =3D 1.5 Mby=

tes/s | 1.5

quoted text
> Mbytes/s * 0.9 =3D 1.2 MBytes/s --> 1.2MBytes/s / 24 bytes =3D 50Kh=

z ... So the

quoted text
> maximum USB 1.0 with 24 bits is 4 chanel in 48KHz...

>

You're absolutely right, the 24 bits 4 channels mode would be only acce=

ssible in

48 kHz samplerate.
> =A0 I would like to know how it works the interface between USB AUDIO =

CLASS device

quoted text
> driver and the USB-AUDIO Alsa Device driver. And how does the isochron=

ous

quoted text
> comunication works inside the kernel? Because I am using an RT Kernel =

and I

quoted text
> would like to set with the high priority this communication.

>

I don't really know how does the isochronous, but applying usual RT sec=

urity

audio rules seems sufficient to get high priority access and then very low<=

br>

latency (got 3 ms here with few audio realtime processes..).
Further info here:

http://joegiampaoli.blogspot.fr/201=

1/06/m-audio-fast-track-pro-for-debian-linux.html
G
--f46d040168f1b3512804cf937a0b--