[LAU] Can netjack1/2 over a direct ethernet connection substitute for local ALSA audio?

crocket crockabiscuit at gmail.com
Thu Mar 28 08:47:12 CET 2019

On Thu, Mar 28, 2019 at 4:06 PM Len <len at ovenwerks.net> wrote:

> Jack can not use two devices. speakers (via some kind of on board audio
> device I assume) and the usb mic will not be in sync and so clicks and
> pops would be assured. Some kind of sample rate conversion would be
> needed. zita-ajbridge or alsa-in would work for that.

Can I not just run two jack servers on Raspberry Pi?

> No, not really. Many applications can talk to jack directly but many do
> not... but then there are more and more that do not talk to alsa either.
> Most linux desktop audio is not alsa (surprise) but pulse. Bridging
> pulse to jack will allow desktop audio to feed jack directly. Pulse does
> present an alsa port for things that do not know about pulse.

My Gentoo Linux desktop doesn't have pulseaudio. It only has ALSA at this
moment. I do not want pulseaudio.
On Gentoo Linux, everything can be compiled against ALSA.
Even, firefox is compiled against ALSA on my gentoo system.
In the same way, if an application uses jack API, I can make it use jack by
compiling them against jack.
I can make firefox use jack by compiling it against ALSA and jack.

> No, but that is not a given with almost anything anyway. Your TV may
> have video and audio in sync, but that sync will change just by moving
> your chair closer or farther away. Audio can lag video by quite a lot
> without being noticeable. Leading, not so much. Some video players (like
> VLC) have a control to move the timing of the audio with respect to the
> video. in this case, just changing the buffer size in jack will add more
> delay. I think what you really want to know is if there will be a
> noticeable difference between when the person on screen moves their lips
> and their voice happens

I want the voices to not lag too much behind the lips.

> However, without knowing what your expectations are and what your use
> is, it is hard to know what to suggest. Pulse also has a plugin that
> allows audio over ethernet and that may be all you need and simpler to
> install. A usb mic is not a serious recording device though maybe ok for
> podcast types of things. I won't say you can't use it for music as great
> recordings have been made with sm57 mics after using them as hammers
> too... but live recordings are more about being there than quality
> sound. crowd noise etc. covers a lot.

I just want Raspberry Pi and my desktop to share my speakers. Raspberry Pi
will serve as a morning alarm, and I need to watch videos on my desktop
I use a USB microphone for foreign language practice and audio calls.
I can technically buy a USB hub that supports per-port power switching to
have my USB microphone turned off most of the time.
But, since Raspberry Pi 3 B+ supports per-port power switching, I wanted to
know whether I could use Raspberry Pi as a network USB hub or a network USB
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