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Stream two audio tracks into different outputs (i.e. headphones and speakers)

Let’s say you have video file (movie, TV series, whatever) with two audio tracks (Language 1, Language 2). Idea is to watch same video with on two languages simultaneously. Of course, you need two audio outputs. It can be speakers and headphones. Ok, let me share my method. BTW, i was encouraged to do this by a message in VLC dev mailing list 1.

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Prerequisites: – Linux (Arch linux in my case) with pulseaudio – VLC media player – Two sound devices (built-in speakers and USB headphones) – Understanding basics of PulseAudio (such as sink, source)

Number #1: Start VLC in following mode

vlc -q --sout-all --sout '#display' <VIDEO_FILE>

Number #2: Redirect Audio input to vacant Audio output (Sink)

pacmd move-sink-input $AUDIO $SINK

To get SINK use

pacmd list-sinks

To get AUDIO use:

pacmd list-sink-inputs

Here is the dumb script that will check if you have two inputs and two outputs and will move input to vacant output.

#!/bin/bash

fail () {
  echo "ERROR: $1"
  killall vlc
  exit 1
}

check () {
  NUM_OF_AUDIO=$(pacmd list-sink-inputs|grep index|wc -l)
  NUM_OF_SINKS=$(pacmd list-sinks|grep index|wc -l)

  [[ $NUM_OF_AUDIO != '2' ]] && fail "Only 2 audio inputs supported. Current is $NUM_OF_AUDIO"
  [[ $NUM_OF_SINKS != '2' ]] && fail "Only 2 audio outputs supported. Current is $NUM_OF_SINKS"
}

SINK1="alsa_output.pci-0000_00_1b.0.analog-stereo"
SINK2=$(pacmd list-sinks|grep -v $SINK1|grep -m1 name:|cut -f2 -d'<'|tr -d '>')

vlc -q --sout-all --sout '#display' $1 &

sleep 1
check

AUDIO1=$(pacmd list-sink-inputs |awk '/index/{i++}i==1{print; exit}'|cut -d':' -f2|tr -d ' ')
AUDIO2=$(pacmd list-sink-inputs |awk '/index/{i++}i==2{print; exit}'|cut -d':' -f2|tr -d ' ')

echo $SINK1 $SINK2
echo $AUDIO1 $AUDIO2

set -x
if [[ $(pacmd list-sink-inputs|grep $SINK1|wc -l) == '2' ]]
then
  pacmd move-sink-input $AUDIO2 $SINK2
else
  pacmd move-sink-input $AUDIO2 $SINK1
fi
set +x

Disadvantages: – Dis-synchronizing video and audio after some time – Pausing breaks sound

References: 1 – https://mailman.videolan.org/pipermail/vlc-commits/2011-April/006155.html