Re: VT8233/A/8235 Clock Problem - good results, some possible bugs?

[Mark Knecht <markknecht@comcast.net>]

On Mon, 2003-12-08 at 13:04, Sergey Vlasov wrote:

> Most likely you need the dxs_support option instead of ac97_clock.
> 
> With dxs_support=2 the sound should work fine, but the hardware mixing
> capability will be disabled.  Then you can try dxs_support=1 or
> dxs_support=4.
> 
> By default snd-via82xx uses dxs_support=3 (except for certain known
> motherboards), this makes only 48000 sampling rate available.  The
> ALSA library can perform resampling for ALSA apps, and the kernel OSS
> emulation layer can do resampling for OSS apps, but the quality is
> often not good.

Sergey,
   Thanks for sending me down this path. Definitely I'm getting better
results now. I did find some things out though. Some may possibly be
bugs:

1) On my system dxs_support=3 is NOT the same as not setting dxs_support
at all. With dxs_support not set I get horrible results. With
dxs_support=3 I get reasonable to good results.

2) **ALL** applications I tried (alspalayer, gxine & xmms) are
overdriving the audio path somewhere and causing distortion. The output
level from the motherboard is not hot. In fact, even when the apps are
up full the output level is actually down about 12-15db from where I'd
like it, but I'm getting lots of distortion. When I reduce alsaplayer's
level the distortion mostly goes away, although I'm left with
considerable background hiss. In all cases I monitored the return level
and it never causes my inputs to clip. (This level difference may be a
pro equipment/consumer equipment issue.)

3) With dxs_support=1 I get very bad sounding results. It appears that
there is a bug in the ADC setting. PCM ADC is set to 48K. I think this
is the mode I would really like to use if PCM ADC was set to 44.1K, but
as it is it sounds terrible. dxs=2 is not very good, and dxs=3/4 are
both pretty good. All modes have a lot of hiss compared to my HDP 9652
and outboard D/A. (Expected...)


cat /proc/asound/card0/codec97#0/ac97#0-0

		   dxs=1	dxs=2		dxs=3/4
<SNIP>
PCM front DAC    : 44100Hz	22050Hz		48000Hz
PCM Surr DAC     : 44100Hz	22050Hz		48000Hz
PCM LFE DAC      : 44100Hz	22050Hz		48000Hz
PCM ADC          : 48000Hz	22050Hz		48000Hz
SPDIF Control    : 44.1kHz	44.1kHz		48000Hz

Sound Quality:	   BAD!!	not good	Good

So, I am currently using Mode 4 and getting pretty good results,
although I think Mode 1 would be even better for me if the PCM ADC was
set to the right value.

Cheers,
Mark



-------------------------------------------------------
This SF.net email is sponsored by: SF.net Giveback Program.
Does SourceForge.net help you be more productive?  Does it
help you create better code?  SHARE THE LOVE, and help us help
YOU!  Click Here: http://sourceforge.net/donate/