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

Len len at ovenwerks.net
Thu Mar 28 08:06:15 CET 2019

On 2019-03-27 22:35, crocket wrote:
> I have a desktop computer and Raspberry Pi 3 B+.
> I want Raspberry Pi to control my speakers and share my speakers with
> my desktop over a direct ethernet connection.

Netjack can do that yes. Or zita-njbridge.
> USB microphone is going to be connected to Raspberry Pi and be shared
> with the desktop computer over the ethernet connection, too.

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 netjack1/2 over a direct ethernet connection substitute for local
> ALSA audio?

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.

> Will video and audio synchronize if netjack was used over a direct
> ethernet connection?

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

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.

Len Ovens

More information about the Linux-audio-user mailing list