PulseAudio

This page goes into detail on using PulseAudio on Linux systems. PulseAudio is used when XBMC is installed in a desktop-environment rather than a dedicated/direct boot setup. PulseAudio allows normal video & audio playback in XBMC while at the same time allowing the user to get audio in their browser or other applications. It also allows XBMC playback of video or audio to be paused in order to run a game, Skype or similar. XBMC is set to only use PulseAudio if you have installed it and running.

History
In the past users have experienced problems with audio not working within XBMC, because they were running a full-blown Ubuntu desktop environment with PulseAudio installed. This happened because PulseAudio blocked the device XBMC required, and audio playback only worked reliably when using the virtual Pulse device.

Our workaround for those users has been to uninstall PulseAudio which completely broke desktop audio.

For XBMC 13 'Gotham' and later we wanted this situation to change, so thanks to the new PulseAudio Sink users now can run a normal Ubuntu desktop.

PulseAudio Output Configuration
PulseAudio will be automatically detected and selected in XBMC when it is running.

PulseAudio can be run in one of two modes these are:

Passthrough Mode Used if you want to passthrough (bitstream) AC3, DTS, and EAC3 to an AVR or other device. In order to allow passthrough to work with PulseAudio then it MUST be set to use a 2.0 channel configuration, despite the 2.0 setting this will still allow 5.1 audio from AC3, DTS, and EAC3.

Multichannel Mode

Used if you want Multichannel PCM out, in this mode you can configure PulseAudio for up to 7.1 channels. In this mode XBMC must decode all audio formats to PCM for passing onto the PulseAudio, this can have the advantage of improve audio/video sync.

Passthrough Mode
In order to activate Passthrough Codecs, just setup pavucontrol, as in the following:

If you like to do this from the command line, issue: pactl set-sink-formats 0 "pcm; ac3-iec61937; dts-iec61937; eac3-iec61937"

Where 0 is the sink you want to alter. You can print all sinks, by using: pactl list sinks You can leave out the codecs your AVR does not support, always keep pcm.

Multichannel Mode
To configure instead Multi channel mode, do the following settings.

Setup Guide
(1) Where TV can decode 5.1 AC3.

(2) Where AVR only has SPDIF which will support 5.1 AC3 & DTS.

(3) Where AVR can do 5.1 PCM.

(4) Where AVR has HDMI inputs but can't decode TrueHD or DTS-HD but does support 5.1 Ac3 or DTS.

(5) Where AVR has full decode capabilities including 7.1 PCM.

Combined Output aka dual audio
If you want to output to all your attached devices in parallel, e.g. HDMI out, analog out and USB sound card, it is enough to do as below:

Step 1: Edit

load-module module-combine-sink sink_name=combined Step 2: Restart pulseaudio. killall pulseaudio

xbmc will then pickup the device, it is named combined.

Audiophile Pulse User
Pulseaudio resamples everything that does not match the underlaying sink, so if you are an audiophile user, you perhaps want to hear your 96 / 192 khz and 24 bit recordings as exact as possible. Therefore you need to tell pulseaudio to use a better resampler in general and second change the default sample rate to 96 or 192 khz. Pulseaudio does not resample audio, that is already in the correct samplerate. Furthermore you need to take care, that your sink has a wide enough output format.

To do this configuration systemwide (96 khz in that example), change /etc/pulse/daemon.conf to include (please replace already existing lines and also remove the commenting):

default-sample-format = s32le default-sample-rate = 96000 resample-method = speex-float-5

The last setting will increase the resample quality from pulse and therefore the CPU load quite a lot. Again: Resampling is only done, when the sink output does not match the data you throw onto it. But as most normal mp3s are in 44.1 khz, you need to take great care when upsampling them. The overwriting of the resample-method is for this use case.

Known issues
When your audio is much too fast or crackles a lot, you might have a broken driver in use. If this is the case, add tsched=0 to the udev loading section in /etc/pulse/default.pa to read like:

load-module module-udev-detect tsched=0