Sound server issue

Christian Hiris 4711 at
Thu May 6 03:41:29 PDT 2004

On Wednesday 05 May 2004 18:06, David Wassman wrote:
> I finally got it working using the manual settings in the LINT file. My
> last question is how to configure the secondary DMA channel. The man
> pages for sbc:
> 	The value of flags specifies the secondary DMA channel.  If the
> secondary DMA channel is C, set the flags to (C | 0x10). For a sound
> card without the secondary DMA channel, the flags should be set to
> zero.
> This is the sbc0 I am using
> 	device sbc0 at isa? port 0x220 irq 5 drq 1 flags 0x15
> I know the settings for the card (they are set in the BIOS). It has a 8
> bit channel at DMA 1 and a 16-bit at DMA 5. Am I right in guessing that
> [drq 1] is the DMA designation? And then how do you get the second DMA
> channel active?

man device.hints explains that drq is the DMA channel number. You enable the 
secondary DMA channel 5 by passing "flags 0x15" to the sound driver.
If i read the ess.c source correctly, for pcm-playback, the secondary DMA 
channel only will be used in duplex mode. The interesting point is that 
duplex mode is disabled by default in the ess driver. The author of the 
program writes: /* audio2 never generates irqs and sounds very noisy */ 

> I think I only have 8-bit sound as wav files are 
> sounding pretty crappy. Am I right in thinking that the man page should
> read like this:

Did you try to overide the default sound device in your apps to /dev/dspW0.0 
or /dev/dspW0.1? man pcm describes how to play around with the DMA 
bufferspace size.
Details of the ESS1869 are available in the chipset specs:

> 	If the secondary DMA channel is C (where C is the number of the
> DMA channel) then set the flags to (C | 0x10)

Yes, the bitwise or ensures that bit 4 in flags is set.

> Or is C a DMA channel of some weird type?

no :-) maybe C means Channel.


> Again thanks for the help.
> David Wassman
> Halcyon DIR Dive Systems
> Director of Technical Services and Quality Control
> Office: 1-800-425-2966 ext 315
> Fax: 386-454-0815
> Email: Wassman at
> > freebsd-questions at mailing list
> >
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