HDSP Line Out Volume Control?

HDSP Line Out Volume Control?

[drclaw]

Hi, I've got an HDSP (Multiface + Cardbus) and I can't figure out how to
get output on the line out that isn't either 0% or 100%.  Basically, if
I don't use the module option "line_outs_monitor=1" I can't hear
anything, but if I do use it, the volume is cranked and distorted.
Also, what exactly is the "matrix mixer"?  Is this related to the
problem of this "matrix mixer" being so complex?  

Thanks,

784 - Michael C. Piantedosi - drclaw@dogsolitude.org


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Re: HDSP Line Out Volume Control?

[Marcus Andersson]

Hi,

you must use the matrix mixer for this. There are no simple controls
defined for the line out. The matrix mixer can mix any combination of
input and playback streams to any of the outputs. This means there are
52x28 = 1456 control values to set.

I have not tested the matrix mixer myself, and right now I don't have my
soundcard at home. I can do some more tests tomorrow. My guess is that
the inputs are numbered 0-25, the playbacks 26-51. The line out signals
have number 26 and 27. If you want to send 50% of the first and second
playback channels to line out, you will have to set the matrix mixer
with something like:

26, 26, 32768
27, 27, 32768

It would be interesting to hear if it works. I have been thinking of
writing a GUI to cotrol the matrix mixer. Maybe someone else has the
same idea.

Marcus

drclaw@dogsolitude.org wrote:
> 
> Hi, I've got an HDSP (Multiface + Cardbus) and I can't figure out how to
> get output on the line out that isn't either 0% or 100%.  Basically, if
> I don't use the module option "line_outs_monitor=1" I can't hear
> anything, but if I do use it, the volume is cranked and distorted.
> Also, what exactly is the "matrix mixer"?  Is this related to the
> problem of this "matrix mixer" being so complex?
> 
> Thanks,
> 
> 784 - Michael C. Piantedosi - drclaw@dogsolitude.org
> 
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Re: HDSP Line Out Volume Control?

[Thomas Charbonnel]

On Wed, 2002-11-20 at 22:12, Marcus Andersson wrote:
> Hi,
> 
> you must use the matrix mixer for this. There are no simple controls
> defined for the line out. The matrix mixer can mix any combination of
> input and playback streams to any of the outputs. This means there are
> 52x28 = 1456 control values to set.
> 
> I have not tested the matrix mixer myself, and right now I don't have my
> soundcard at home. I can do some more tests tomorrow. My guess is that
> the inputs are numbered 0-25, the playbacks 26-51. The line out signals
> have number 26 and 27. If you want to send 50% of the first and second
> playback channels to line out, you will have to set the matrix mixer
> with something like:
> 
> 26, 26, 32768
> 27, 27, 32768
> 
> It would be interesting to hear if it works. I have been thinking of
> writing a GUI to cotrol the matrix mixer. Maybe someone else has the
> same idea.
> 
> Marcus

I asked Paul once about the matrix mixer.
His answer was :

<quote>
first value: input source
second value: output source
third value: gain

input source: 0-25  (physical channels), 26-51 (audio output streams)
output source: 0-27 (physical channels)

output channels 26 and 27 are the two line outs on the I/O box.
</quote>

As Michael is stating, full volume (100% in alsamixer, or full 65536
value in the matrix mixer) causes distortion. 50%, or 32786, seems to be
the highest distortion-free value. I already mentioned this on the list
but got no answer.

I succesfully tested the matrix mixer, using both amixer and the alsa
mixer api. Here's an amixer example with the values you picked above :
amixer cset numid=5 26,26,32786
amixer cset numid=5 27,27,32786

I wanted to write a gui to the matrix mixer, but I haven't started yet
(still wondering what toolkit to use, if any, as hacking alsamixer may
be the easiest way). So far I only quickly hacked seqdemo, by Matthias
Nagorni, to control the LineOut output of the physical inputs of the
multiface with my Peavey PC 1600x fader box.
One thing that bothers me is the fact one can't get the state of the
matrix mixer, it's just possible to set it (am I wrong, Paul ?). One
other is the way to handle channels when the adat channels are used at
96Khz, dividing their number by two. One more is that matrix mixer
operation should be integrated in jack too, to handle hardware
monitoring, and that it should operate smoothly with the future matrix
gui.

Thomas




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Re: HDSP Line Out Volume Control?

[Patrick Shirkey]

Thomas Charbonnel wrote:
> 
> I asked Paul once about the matrix mixer.
> His answer was :
> 
> <quote>
> first value: input source
> second value: output source
> third value: gain
> 
> input source: 0-25  (physical channels), 26-51 (audio output streams)
> output source: 0-27 (physical channels)
> 
> output channels 26 and 27 are the two line outs on the I/O box.
> </quote>
> 
> As Michael is stating, full volume (100% in alsamixer, or full 65536
> value in the matrix mixer) causes distortion. 50%, or 32786, seems to be
> the highest distortion-free value. I already mentioned this on the list
> but got no answer.
> 
> I succesfully tested the matrix mixer, using both amixer and the alsa
> mixer api. Here's an amixer example with the values you picked above :
> amixer cset numid=5 26,26,32786
> amixer cset numid=5 27,27,32786

This is the kind of information that should be submitted as a note to 
the alsa-docs. If you submit it then people will associate your name 
with the info.

Currently not one person has provided anything for the advanced multi 
channel devices :(


-- 
Patrick Shirkey - Boost Hardware Ltd.
For the discerning hardware connoisseur
Http://www.boosthardware.com
Http://www.djcj.org - The Linux Audio Users guide
========================================

Being on stage with the band in front of crowds shouting, "Get off! No! 
We want normal music!", I think that was more like acting than anything 
I've ever done.

Goldie, 8 Nov, 2002
The Scotsman



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Re: HDSP Line Out Volume Control?

[Thomas Charbonnel]

On Thu, 2002-11-21 at 16:10, Patrick Shirkey wrote:

> This is the kind of information that should be submitted as a note to 
> the alsa-docs.

You're right, it's done.




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Re: HDSP Line Out Volume Control?

[Marcus Andersson]

Thomas Charbonnel wrote:
> As Michael is stating, full volume (100% in alsamixer, or full 65536
> value in the matrix mixer) causes distortion. 50%, or 32786, seems to be
> the highest distortion-free value. I already mentioned this on the list
> but got no answer.

32768 is 0dB
65535 is +6dB

It distorts at 100% if you output a signal louder than -6dBFS.

Marcus


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Re: HDSP Line Out Volume Control?

[Thomas Charbonnel]

On Thu, 2002-11-21 at 23:38, Marcus Andersson wrote:
> 32768 is 0dB
> 65535 is +6dB
> 
> It distorts at 100% if you output a signal louder than -6dBFS.

I came across this point outputing OdB sine waves with pd that sounded
like square with channel volume at 100%.
Things get much clearer now, thanks a lot.
You should post an addendum on the alsa-project.org hdsp page,
correcting my double (as 2^15 != 32786) mistake concerning the range of
the gain parameter of the matrix mixer.

Thomas




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