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Date:      Fri, 21 May 1999 21:42:02 -0500
From:      Karl Denninger <karl@Denninger.Net>
To:        hackers@freebsd.org
Subject:   New one - mp3 "clicks" during playback
Message-ID:  <19990521214202.A16648@Denninger.Net>

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Hi folks,

I've gotten my Ensoniq card installed and the driver configured, and it
works - sorta.

mpg123 has been the recommended "playback" mode for MPG files.  Well and
fine.    Except for one small problem:

	If the system starts taking interrupts, I get "clicks", roughly
	consonant with the interrupts, in the output.  They're solidly
	correlated with disk activity.

Now I could see if the system was busy for a long period of time that it
could "get behind" whatever buffering is in the sound board, and you'd be
screwed (due to data starvation).  But this looks to be something different
- it looks like there is NO buffering on the card at all, and that even
the interrupt traffic causes stream disruption in the output.

This can't be right - or is it?

If it is, then any I/O during playing a sound file of some kind is going to
lead to unacceptable interruptions and poor sound quality.

Mpg123 seems to consume about 12% of the CPU when its running - I have a
Pentium Pro 200 in this box.  "vmstat" shows a 0.12 system load during
a run, so I should be well within the boundaries.

"mpg123's" buffering option (-b) doesn't affect the display of this problem
in any appreciable way.

Is this my hardware?  This is a rather old Soundscape board, but I can't
imagine they've changed that much.  If the answer is to use a different
card (one that has some buffering internally!) that's ok with me - what
should I install instead?

I DID note that the Ensoniq driver seems to want the Soundscape board
on IRQ 9.  That's a rather problematic interrupt to use in my experience
in the past - is this part of the issue (the disks are on Adaptec PCI
controllers)?

Ideas?  As it stands the decoder is useless in any environment where
the system might actually have to do something while it's running.

--
-- 
Karl Denninger (karl@denninger.net)  Web: fathers.denninger.net
I ain't even *authorized* to speak for anyone other than myself, so give
up now on trying to associate my words with any particular organization.



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