About

Control a realtime netjack2 connection between two machines.

Usage

Use the jackpod command to set up a netjack2 connection (jackpod -r j) and optionally start a pulseaudio sink (jackpod -r p, see pactl list sinks).

jackpod [-S | -k (jpP) | -r (jpP) ] [-w -d]

j = local and remote jackds in netjack2 mode
p = pulseaudio sink "jack_out"
P = pulseaudio service

options:
    -S       : show status
    -k (jpP) : kill stuff
    -r (jpP) : start or restart
    -w       : wifi mode (use more buffering, pay with increased AV delay)
    -d       : debug mode: write a logfile /tmp/jack.log on the local and remote
               machine

-r p: when we resume from suspend (to ram) mode, then the jackd connection
(netjack2) is still active and only the pulse sink needs a restart -> no need
to kill the jackds, which takes a bit longer.

examples:

    This is what you call when you need to start all
        $ jackpod -r jp

    Check status
        $ jackpod -S
        remote jackd    yes
        local jackd     yes
        jack_out sink   yes

    (Re)start all, including pulseaudio
        $ jackpod -r jpP

    Disable pulse sink
        $ jackpod -k p
        $ jackpod -S
        remote jackd    yes
        local jackd     yes
        jack_out sink   NO

    Restart only pulse sink (e.g. after resuming from suspend mode)
        $ jackpod -r p

    Activate wifi settings:
        $ jackpod -r jp -w

See README_jack.md for details.

The sound flow is either (no pulse sink):

app (e.g. mpv --ao=jack) -> jackd (slave) -- LAN --> jackd (master) -> sound card

or with the pulse sink jack_out:

app (e.g. mpv --audio-device=pulse/jack_out, browser, ...) -> pulseaudio -> jackd (slave) -- LAN --> jackd (master) -> sound card

For sound sources that cannot select the backend they play on (such as the browser, and unlike mpv which can do that), use pulseaudio's pavucontrol tool to redirect sound to the sink called "Jack sink (PulseAudio JACK Sink)", which is the jack_out sink created with jackpod -r p.

Latency, WiFi, defaults

We hard-coded some values such as

• the master's sound card -- in our case a Raspberri Pi with a Hifiberry DAC
• values which influence the latency

so YMMV. Please just hack the values to fit your setup.

Note that netjack2 is designed to be run over a stable cable connection. We achieve very low latency with no perceptible AV (audio-video) delay in this case -- important for video! There is the -w (WiFi mode) option which sets looser options (more buffering) that will increase the AV-delay a bit. This will need to be adjusted for your network. So far, we had stable connections only via cable or when (i) surrounding WiFis are off, (ii) use very different channels, (iii) we use 5 GHz-only Wifi which is much less crowded (many people still use 2.4 GHz, so less channel overlap). See README_wifi.md for more details.

So .. with a bad Wifi setup, using an Ethernet cable is better .. and one could just as well use a 3.5 mm audio cable instead, right? Sure, but it wouldn't be as cool!