[wdmaudiodev] Re: True latency
- From: "Jerry Evans" <jerry@xxxxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Tue, 22 Apr 2003 09:42:12 +0100
Hi all.
The test rig is simple. I generate tones on one PC and then route the stereo
signal back into the source machine. Along the way one channel is routed via
the UA-20 which is configured to record and playback. By examining the
difference in time between the start of the tone I can get some reasonable
measure of overall latency in the chain. The key assumption here is that the
signals are in phase when they leave the PC running Cool Edit Pro.
ASCII art follows (!)
-------------------------use fixed pitch font-----------------------------
+-----------------+ +---------------------+
| PC running Sonar| <------ USB -------->| Roland UA-20 |
+-----------------+ +---^---------------V-+
+------->-----------+ |
+------------------+ | Left Out to UA20 Left In |
| |->----+ |
| PC |-<-----------Left In from UA20 Left Out --+
| running |
| 2 x CEP |->-----+ Right out looped back
| |-<-----+ onto Right in on signal source PC
+------------------+
----- Original Message -----
From: "Mike Kent" <mikekent@xxxxxxxxxxxxxx>
To: <jerry@xxxxxxxxxx>
Sent: Monday, April 21, 2003 9:46 PM
Subject: Re: [wdmaudiodev] True latency
> > Testing a variety of devices here I find the most striking is the Roland
> > UA20
> > USB device. With Sonar set 1ms latency and 4 buffers I get a measured
> > latency
> > of ~12ms. The test is simple: Use another PC running 2 copies of Cool Edit.
> > Copy 1 generates DTMF tones and sends them via a splitter cable that loops
> > back into the second PC. One channel is routed via the 'remote' signal
> > chain.
> > Copy 2 records from the input where it is then possible to see the
> > differences
> > in the 2 channels.
> >
> > Has anyone else tried something similiar ? Any numbers to swap ?
>
>
> Jerry,
>
> Is your 12ms the Output latency? Or combined Out + In latency?
> I'm not sure I understand your testing setup.
>
> > most striking is the Roland UA20
>
> Striking in what way?
> What other devices have you tested?
>
> Regards,
> Mike.
>
> -----------------------------------------------
> | Mike Kent, Manager of Technical Relations |
> | Roland Corporation |
> | Email: mikekent@xxxxxxxxxxxxxx |
> | Tel: (604)543-2973 Fax: (604)543-2983 |
> -----------------------------------------------
>
>
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