[LAU] Help with jack-volume please

drew Roberts zotzbro at gmail.com
Wed Feb 17 16:52:12 CET 2021


Thanks for the feedback.

On Wed, Feb 17, 2021 at 10:30 AM Len Ovens <len at ovenwerks.net> wrote:

> On Wed, 17 Feb 2021, drew Roberts wrote:
> > I am not 100% sure I understand it all correctly, but here is what I am
> > working on in my effort to help:
> >
> > "I have program Audio that will be coming in as AES to the input of the
> > Audio Science card (ASI6644)"
> AES3 I presume. So stereo program.

I guess. I have never played in that field.

> > This comes into the machine with the ASI card and gets sent back out to a
> > speaker as analog audio. It is intended to play without stopping.
> OK
> > At 10 minutes past every hour, it should be faded down and specific files
> > played out to the same speaker.
> The ASI6644 Has Linux alsa drivers, why not use amixer to change the level
> of the program audio going into the card (and out if needed).

Ignorant question: How would you script that? How do you detect when the
file playback ends and turn the regular volume back up?

> > I initially thought of liquidsoap. I get so far and then my skills fail
> me.
> > It seems it should be easy but it is stumping me. I have one more
> thought to
> > perhaps annotate things somehow or whatever.
> Unless you actually need a streaming capability to extend across a network
> (you say aes3 in and audio out so no)

I see no mention of the need to stream. Or perhaps he knows how to do that
part "outside" of this.

> > So, I now have a jack graph.
> Basically you are using jackd to mix the two signals then which is ok. I
> am not sure what other options are available and jack is probably easiest
> to do. I am not that familiar with the ASI6644 (or any audio science card)
> as they are out of my price range :) but I think it may be possible to mix
> two sets of playback channels in the card itself as it seems to have a
> matrix mixer on the card. This would eliminate the use of jack all
> together. I do not know if the ALSA driver has all the control showing in
> ALSA or if a more direct control is needed. The card does have an API to
> allow custom control applications to be set up.
> You also mentioned something about a R-pi... My first question for that
> would be, does the R-pi have a PCIe slot?

He has the nice card, I have the R-pi... ~;-)

> I know that some SOC cards do
> but my old R-pi 2 most certainly does not :)  However, if you are testing
> on a R-pi then I would assume you have a USB device...

I do have an inexpensive ub, no capture controls, 1 playback (PCM).

> many of these do
> not have mixer controls available to ALSA, using real knobs instead. The
> very cheap USB dongles with mic in and headphone out do have ALSA mixer
> controls and might be better for testing.

I still have the feeling that someone who knows what they are doing in
liquidsoap could to it all there very easily.

I have asked something in #savonet on irc. No response yet.

I am learning a lot in this process that may be useful later so I am happy
enough to experiment...

> --
> Len Ovens
> www.ovenwerks.net

all the best,


Enjoy the *Paradise Island Cam* playing
*Bahamian Or Nuttin* - https://www.paradiseislandcam.com/
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