[PATCH]snd-usb-usx2y yields much better latency....

[PATCH]snd-usb-usx2y yields much better latency....

[Karsten Wiese]

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....with the default setting as in this patch.

Please commit with comment
	- set NRPACKS to 1 as default setting to improve latency.

Thanks & Regards
Karsten


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Index: alsa-driver/usb/usx2y/usbusx2y.h
===================================================================
RCS file: /cvsroot/alsa/alsa-driver/usb/usx2y/usbusx2y.h,v
retrieving revision 1.5
diff -u -r1.5 usbusx2y.h
--- alsa-driver/usb/usx2y/usbusx2y.h	15 Jun 2004 10:55:39 -0000	1.5
+++ alsa-driver/usb/usx2y/usbusx2y.h	24 Jun 2004 19:47:34 -0000
@@ -5,7 +5,13 @@
 #include "usbus428ctldefs.h" 
 
 #define NRURBS	        2	/* */
-#define NRPACKS		2	/* usb-frames/ms per urb: 1 and 2 are supported. set to 1 if you want lowest possible latency */
+#define NRPACKS		1	/* usb-frames/ms per urb: 1 and 2 are supported.
+				   setting to 2 will PERHAPS make it easier for slow machines.
+				   Jitter will be higher though.
+				   On my PIII 500Mhz Laptop setting to 1 is the only way to go 
+				   for PLAYING synths. i.e. Jack & Aeolus sound quit nicely 
+				   at 4 periods 64 frames. 
+				*/
 
 #define URBS_AsyncSeq 10
 #define URB_DataLen_AsyncSeq 32

Re: [PATCH]snd-usb-usx2y yields much better latency....

[Clemens Ladisch]

Karsten Wiese wrote:
> ....with the default setting as in this patch.
>
> Please commit with comment
> 	- set NRPACKS to 1 as default setting to improve latency.

Applied, thanks.

> -#define NRPACKS      2
> +#define NRPACKS      1

The generic driver uses a module option for this.  It might be a good
idea to have consistent behaviour in both drivers.


Regards,
Clemens




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Re: [PATCH]snd-usb-usx2y yields much better latency....

[Takashi Iwai]

At Fri, 25 Jun 2004 17:19:13 +0200 (METDST),
Clemens Ladisch wrote:
> 
> Karsten Wiese wrote:
> > ....with the default setting as in this patch.
> >
> > Please commit with comment
> > 	- set NRPACKS to 1 as default setting to improve latency.
> 
> Applied, thanks.
> 
> > -#define NRPACKS      2
> > +#define NRPACKS      1
> 
> The generic driver uses a module option for this.  It might be a good
> idea to have consistent behaviour in both drivers.

More better would be to merge them ;)
Or we can split the common part from usb-audio.

Anyway, if usx2y works stably, it's nicer to have it on 2.6 kernel
tree, too.


Takashi


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