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{{mininav|[[Development]]{{l2|[[Audio]] }} }}
'''AudioEngine''' (or AE) refers to XBMC's new audio system, a two-year project spear-headed by [[gnif]] which is intended to be released in v12 (Frodo), and has been merged with master for user testing as of May 15th, 2012. Why a new audio subsystem?


It's been an accepted fact that the existing audio code was little-touched since the early days of XBMC, and was limited by the 16-bit architecture of the original XBox and codecs available at the time. Dolby AC3 and mp3 (or earlier formats!) ruled the media codec world. Over time HTPC's became more mainstream, more powerful and better connected. Analog gave way to optical SPDIF connections, in turn replaced with HDMI. Processors, GPU's and media formats evolved at a steady pace.
'''AudioEngine''' or ('''AE''') refers to XBMC's new audio system.  
 
With the growth of the HTPC and new formats like those made available with Bluray technology, the audio subsystem was under scrutiny as an area for improvement. Higher definition audio like multichannel FLAC was becoming a preferred standard for those demanding higher quality audio media. It was time for an update, and what an update!
 
== History and Team ==
Early efforts at patching fixes and even an initial attempt at a completely new system fell by the wayside. The scope of the required changes and the complexity of the API made it a daunting task, especially for volunteer programmers working in their spare time.  This was compounded by the fact that XBMC runs on a wide range of hardware and operating systems.  Most of the developers focus on specific platforms or subsystems within the whole of XBMC. Any new system had to be platform-agnostic, cohesive and flexible.
 
In time, it became obvious the project was going to require a full re-write and replacement of the audio engine. Furthermore, XBMC's base of hardware and OS platforms continued to grow. The detailed specifications for the new audio formats were unknown, and of course the master code for XBMC was ever-changing.
 
In November of 2009 [[gnif]] decided to bite the proverbial bullet, and after extensive consultation with the team finalized the API or structure which was to become AE. Drawing in other dev's as required, the massive project slowly took shape, and reached the ready-point for user tests a year later. The forum thread for those hardy beta-testers (thank you!) reached over 1,200 posts, and slowly but surely features were added and debugged, and system stability grew.
 
Over the next two years, thanks to the determination of [[gnif]] the core engines, decoders, encoders and utilities that make up '''AudioEngine''' became a reality, and other developers began to contribute to the core and especially the platform-specific sinks or output stages. Among those contributing were [[gimli]], [[fneufneu]], [[memphiz]], [[dddamian]], [[anssi]] and others.
 
There was a goal to have the new audio system ready for Eden 11.0, but there was just too much left to do. Many users were eagerly looking forward to it's inclusion, but stable releases must continue, and AE wasn't ready when the Eden feature-freeze went into effect. During this time the AE code-base was solidified, bugs tracked and squashed, features added and testing increased.
 
On May 15th 2012, [[AudioEngine]] was merged to master. Weighing in at over 22,000 lines of code, it represents one of the single biggest code-merges ever for XBMC. Now for the first time it is readily accessible for all the development team (and users!) to see, test and improve within the greater context of XBMC's master branch.
 
Team XBMC is proud to at last unveil '''AudioEngine''', bringing HD audio to XBMC!


== Features ==
== Features ==
AudioEngine replaces SDL and brings some of the external dependencies into XBMC, and wraps up all the different media types for mixing, samplerate conversion, format conversion, encoding, upmix, downmix, etc.
<br />
;Features of AE include:
;Features of AE include:
* ''support for DTS-MA / Dolby TrueHD Bluray formats''
* ''Support for DTS-HD MA / Dolby TrueHD Bluray formats''
* ''support for 24-bit and floating-point audio at up to 384,000hz''
* ''Support for 24-bit and floating-point audio at up to 384,000hz''
* ''mixing of all streams including GUI sounds even when transcoding audio''
* ''Mixing of all streams including GUI sounds even when transcoding audio''
* ''start-up enumeration of hardware audio devices and their capabilities with log output''
* ''Start-up enumeration of hardware audio devices and their capabilities with log output''
* ''bitstreaming support in [[PAPlayer]] (XBMC's music player)''
* ''Bitstreaming support in PAPlayer (XBMC's music player)''
* ''upmixing of stereo to full channel layout''
* ''Upmixing of stereo to full channel layout''
* ''tighter syncing of A/V streams''
* ''Tighter syncing of A/V streams''
* ''floating-point processing of audio''
* ''Floating-point processing of audio''
* ''24-bit and floating-point decoding/handling of mp3''
* ''24-bit and floating-point decoding/handling of mp3''
* ''full support for [[w:ReplayGain|ReplayGain]]''
* ''Full support for [[w:ReplayGain|ReplayGain]]''
* ''built-in sample-rate conversion and transcoding''
* ''Built-in sample-rate conversion and transcoding''


It's still early days for AE. Bugs will be found, and new and exciting features added.


;Planned Features for upcoming AE releases:
== Settings ==
* ''rules-based decisions for output formats based on hardware capabilities''
Audio settings can be found in the GUI at
* ''a range of DSP's (digital signal processors) including headphone head-related transfer function processing, DRC (dynamic range compression), low-pass filtering for subs and an equalizer function''
* ''custom channel-mixing/mapping for up and downmixing''


;<big>{{highlight|Settings -> System -> Audio output|bordered=yes}}</big>


It's still early days for AE. Bugs will be found, and new and exciting features added. If you want to give it a try just grab one of the [[nightly versions]] on one of XBMC's mirrors.


AudioEngine replaces SDL and brings some of the external dependencies into XBMC, and wraps up all the different media types for mixing, samplerate conversion, format conversion, encoding, upmix, downmix, etc.
== Supported Audio Formats for Passthrough ==


== GUI Settings ==
A summary of some of the supported formats within the AudioEngine
AE brings several new settings to the graphical user interface (GUI) as well as to [[#Advanced settings|advancedsettings.xml]].


;<big>{{highlight|Settings -> System -> Audio output|bordered=yes}}</big>
{| class="prettytable" style="text-align: center; color: black;"
|-
!rowspan="3" style="color:#000000; background-color:#DBDBDB;" | '''Audio Codec'''
!colspan="12" style="color:#000000; background-color:#DBDBDB;" | '''Audio Source'''
!rowspan="3" style="color:#000000; background-color:#DBDBDB;" | '''XBMC Passthrough Setting'''
|-
!colspan="3" style="color:#000000; background-color:#DBDBDB;" | '''HD DVD'''
!colspan="3" style="color:#000000; background-color:#DBDBDB;" | '''Blu-ray Disc'''
!colspan="3" style="color:#000000; background-color:#DBDBDB;" | '''DVD-Video'''
!colspan="3" style="color:#000000; background-color:#DBDBDB;" | '''DVD-Audio'''
|-
! style="color:#000000; background-color:#DBDBDB;"| Channels (max)
! style="color:#000000; background-color:#DBDBDB;"| Max bit rate
! style="color:#000000; background-color:#DBDBDB;"| Sample rate (max)
! style="color:#000000; background-color:#DBDBDB;"| Channels (max)
! style="color:#000000; background-color:#DBDBDB;"| Max bit rate
! style="color:#000000; background-color:#DBDBDB;"| Sample rate (max)
! style="color:#000000; background-color:#DBDBDB;"| Channels (max)
! style="color:#000000; background-color:#DBDBDB;"| Max bit rate
! style="color:#000000; background-color:#DBDBDB;"| Sample rate (max)
! style="color:#000000; background-color:#DBDBDB;"| Channels (max)
! style="color:#000000; background-color:#DBDBDB;"| Max bit rate
! style="color:#000000; background-color:#DBDBDB;"| Sample rate (max)
|-
| align="left"|'''Dolby Digital (AC-3)'''
| 5.1
| 504 kbit/s
| 48 kHz / 16 bit
| 5.1
| 640 kbit/s
| 48 kHz / 16 bit
| 5.1
| 448 kbit/s
| 48 kHz / 16 bit
| 5.1
| 448 kbit/s
| 48 kHz / 16 bit
| rowspan="2"| Dolby Digital (AC3) capable receiver
|-
| align="left"|'''Dolby Digital Plus (E-AC-3)'''
| 7.1
| 3 Mbit/s
| 48 kHz / 24 bit
| 7.1
| 1.7 Mbit/s
| 48 kHz / 24 bit
| colspan="6" {{NA}}
|-
| align="left"|'''DTS'''
| 5.1 (Core)
| 1536 kbit/s
| 48 kHz / 24 bit
| 5.1 (Core)
| 1536 kbit/s
| 48 kHz / 24 bit
| 6.1
| 768 kbit/s
| 48 kHz / 16 bit
| colspan="3" {{NA}}
| rowspan="2"| DTS capable receiver
|-
| align="left"|'''DTS 24/96'''
| colspan="6" {{NA}}
| 5.1
| 1536 kbit/s
| 96 kHz / 24-bit
| 5.1
| 1536 kbit/s
| 96 kHz / 24-bit
|-
| align="left"|'''Linear PCM (LPCM)'''
| 7.1
| 27 Mbit/s
| 192 kHz / 24 bit
| 8.1
| 27 Mbit/s
| 192 kHz / 24 bit
| 5.1
| 6.1 Mbit/s
| 48 kHz / 16 bit
| 5.1
| 6.1 Mbit/s
| 96 kHz / 24 bit
| MultiChannel LPCM capable receiver
|-
| align="left"|'''Dolby TrueHD'''
| 7.1
| 18 Mbit/s
|192 kHz / 24 bit
| 7.1
| 18 Mbit/s
| 192 kHz / 24 bit
| colspan="6" {{NA}}
| TrueHD capable receiver
|-
| align="left"|'''DTS-HD High Resolution Audio (HRA)'''
| 7.1
| 6 Mbit/s
| 96 kHz / 24 bit
| 7.1
| 6 Mbit/s
| 96 kHz / 24 bit
| colspan="6" style=background:#FFC890 | N/A
| rowspan="3"| DTS-HD capable receiver
|-
| align="left" rowspan="2"|'''DTS-HD Master Audio (MA)'''
| 5.1
| 18 Mbit/s
| 192 kHz / 24 bit
| | 5.1
| 18 Mbit/s
| 192 kHz / 24 bit
| colspan="6" {{NA}}
|-
| 7.1
| 18 Mbit/s
| 96 kHz / 24 bit
| 7.1
| 18 Mbit/s
| 96 kHz / 24 bit
| colspan="6" {{NA}}
|}
 
=== Test audio files ===
Below You can find a excellent range of flac test audio files stereo/multichannel and varied sample/bit rates and quality.


[[File:Settings - Audio Output.png|800px]]
Click [http://www.2l.no/hires/ here] to download flac test files


; Audio output
Click [http://download.wavetlan.com/SVV/Media/HTTP/http-wma.html here] to download wma test files
: Allows you to tell xbmc about the type of connection to the audio equipment. Optical/Coax and HDMI enable the passthrough of Dolby Digital and DTS to capable receivers.
; Speaker Configuration
: select your physical speaker layout
; Boost volume level on downmix
: Boosts AC3 streams that have been mixed-down to 2 channels
{| width="90%" align="center"
|
----
|}
; - Dolby Digital (AC3) capable receiver
: Select this option if your receiver is capable of decoding AC3 streams.
; - DTS capable receiver
: Select this option if your receiver is capable of decoding DTS streams.
; - AAC capable receiver
: Select this option if your receiver is capable of decoding AAC streams.
; - MultiChannel LPCM capable receiver
: Select this option if your receiver is capable of decoding LPCM streams.
{| width="90%" align="center"
|
----
|}
; - TrueHD capable receiver
: Select this option if your receiver is capable of decoding TrueHD streams.
; - DTS-HD capable receiver
: Select this option if your receiver is capable of decoding DTS-HD streams.
{| width="90%" align="center"
|
----
|}
; Audio output device
: device you use to play PCM or decoded audio such as mp3's and FLAC.
; Passthrough output device
: device you use to play encoded formats (those checked in "xyz capable receiver" above).
{| width="90%" align="center"
|
----
|}
; Play GUI sounds
: Interface sounds. Select from never, only when playback stopped, or always.


Click [http://www.testsounds.com/ here] to download various audio system test files


----


== History and Team ==
AudioEngine, AE for short was two-year project spear-headed by [[User:Gnif|Gnif]] which was released in v12 (Frodo), and was first merged with master for user testing as of May 15th, 2012.


;<big>{{highlight|Settings -> Music -> Playback|bordered=yes}}</big>
=== Why write a new audio subsystem? ===


:''Here you can find the settings for [[w:ReplayGain|ReplayGain]] and Cross-Fading music (gapless playback).''
It's been an accepted fact that the existing audio code was little-touched since the early days of XBMC, and was limited by the 16-bit architecture of the original Xbox and codecs available at the time. Dolby AC3 and mp3 (or earlier formats!) ruled the media codec world. Over time HTPC's became more mainstream, more powerful and better connected. Analog connections gave way to optical SPDIF connections, which in turn were replaced with HDMI. Processors, GPU's and media formats evolved at a steady pace.


[[File:Music - Playback.png|800px]]
With the growth of the HTPC and new formats like those made available with Bluray technology, the audio subsystem was under scrutiny as an area for improvement. Higher definition audio like multichannel FLAC was becoming a preferred standard for those demanding higher quality audio media. It was time for an update, and what an update!
; Play the next song automatically
: XBMC automatically plays the next item in the current folder. For example, in Files View: After a track has been played, XBMC would automatically play the next track in the same folder.
; Queue songs on selection
: When songs are added to a playlist they are queued instead of playback starting immediately.
{| width="90%" align="center"
|
----
|}
; Replaygain volume adjustments
: When enabled, XBMC will read the Replay Gain information encoded in your audio files by a program such as [http://mp3gain.sourceforge.net/ MP3Gain] and normalize the sound levels accordingly. You have the option of either using track levels or album levels.
; PreAmp Level - Replay gained files
: level in dB - default is 89dB per standard
; PreAmp Level - Non replay gained files
: level in dB - default is 89dB per standard
; Avoid clipping on replay gained files
: reduce volume of the file if clipping is likely to occur
{| width="90%" align="center"
|
----
|}
; Crossfade between songs
: Enabling this will cause the player to smoothly fade from one audio track to the next. You can set the amount of overlap of the tracks from 1-10 seconds.
; Crossfade between songs on the same album
: You have the option of only crossfading between songs on the same album or all.
{| width="90%" align="center"
|
----
|}
; Visualization
: Determines which visualization will be displayed while listening to music. For more information, see [[Visualizations]].


== Advanced settings ==
Early efforts at patching fixes and even an initial attempt at a completely new system fell by the wayside. The scope of the required changes and the complexity of the API made it a daunting task, especially for volunteer programmers working in their spare time.  This was compounded by the fact that XBMC runs on a wide range of hardware and operating systems.  Most of the developers focus on specific platforms or subsystems within the whole of XBMC. Any new system had to be platform-agnostic, cohesive and flexible.
Current [[advancedsettings.xml]] [[advancedsettings.xml#<audio>|tags]] for AE:


<syntaxhighlight lang="xml">
In time, it became obvious the project was going to require a full re-write and replacement of the audio engine. Furthermore, XBMC's base of hardware and OS platforms continued to grow. The detailed specifications for the new audio formats were unknown, and of course the master code for XBMC was ever-changing.
<advancedsettings>
  <audio>
    <resample>0</resample>
    <forceDirectSound>0</forceDirectSound>
    <audiophile>0</audiophile>
    <audiosinkbufferdurationmsec>50</audiosinkbufferdurationmsec>
    <allowtranscode44100>0</allowtranscode44100>
    <streamsilence>0</streamsilence>
  </audio>
</advancedsettings>
</syntaxhighlight>


''Default values are shown above in the code box - these values are used if that tag does not exist.''
=== Three years of work ===
In November of 2009 [[User:Gnif|Gnif]] decided to bite the proverbial bullet, and after extensive consultation with the team finalized the API or structure which was to become AE. Drawing in other developers as required, the massive project slowly took shape, and reached the ready-point for user tests a year later. The forum thread for those hardy beta-testers (thank you!) reached over 1,200 posts, and slowly but surely features were added and debugged, and system stability grew.


{| class="wikitable"
Over the next two years, thanks to the determination of [[User:Gnif|Gnif]] the core engines, decoders, encoders and utilities that make up AudioEngine became a reality, and other developers began to contribute to the core and especially the platform-specific sinks or output stages. Among those contributing were [[User:Gimli|Gimli]], [[User:Fneufneu|Fneufneu]], [[User:Memphiz|Memphiz]], [[User:Dddamian|Dddamian]], [[User:Anssi|Anssi]] and others.
| '''resample'''
| force resampling of audio at a given frequency e.g. 48000 = 48khz
|-
| '''forceDirectSound'''
| win-specific - will not use Wasapi API 0 = false, 1 = true
|-
| '''audiophile'''
| forces playback of original format, will not down/upmix next song to match current, not compatible with cross-fading 0 = false, 1 = true
|-
| '''audiosinkbufferdurationmsec'''
| win-specific, buffer time in msec, hard minimum of 50msec
|-
| '''allowtranscode44100'''
| allows 44100hz when trancoding for SPDIF devices 0=false, 1=true
|-
| '''streamsilence'''
| forces original AE behaviour where an audio signal is constantly streamed to the audio device, even if silent. If 1 or true, This prevents some receivers from losing the signal/source, and prevents sinks re-opening and possible receiver switching with each new stream after any silence. If 0 or false, enables Eden-style releasing of the audio device so external players, programs and the system can access the audio device, i.e. prevents XBMC from hogging the audio device.
|}


== Hardware reported to work (please add your experience)==
There was a goal to have the new audio system ready for Eden 11.0, but there was just too much left to do. Many users were eagerly looking forward to it's inclusion, but stable releases must continue, and AE wasn't ready when the Eden feature-freeze went into effect. During this time the AE code-base was solidified, bugs tracked and squashed, features added and testing increased.
{| class="wikitable"
| '''Model Name'''
| '''GPU Name'''
| '''GPU Code Name'''
| '''DTS-MA'''
| '''Dolby True HD'''
| '''Dolby Digital Plus'''
| '''Video Driver Version'''
| '''Operating System'''
|-
| Asus EN210
| Nvidia G210
| GT218
| Yes
| Yes
| No
| 302.17
| Ubuntu 11.10
|-
| Asus EN210
| Nvidia G210
| GT218
| Yes
| Yes
| -
| 290.10
| Ubuntu 12.04 LTS
|-
| Asus ENGT430 DC SL DI 1GD3
| Nvidia GT 430
| GF108
| Yes
| Yes
| -
| 295.59
| Ubuntu 12.04 LTS
|-
| Palit GT640 1GB
| Nvidia GT 640
| GK107
| Yes
| Yes
| -
| 304.43
| Ubuntu 12.04 LTS
|-
| AMD A4-3400 APU
| Radeon HD 6410D
| -
| Yes
| Yes
| testing
| 5.12.0.13
| Windows 8 RTM
|}


== Support ==
Finally, on May 15th 2012, AudioEngine was merged to master. Weighing in at over 22,000 lines of code, it represents one of the single biggest code-merges ever for XBMC. Now for the first time it is readily accessible for all the development team (and users!) to see, test and improve within the greater context of XBMC's master branch.
The best place to get support for AE-related issues is the XBMC forum. Several threads exist - reading them will often answer any issues, and of course you can receive assistance there:


*[[forum:78289|Main AE forum thread]]
=== ActiveAE ===
*[[forum:124600|Windows AE forum thread]]
ActiveAE was a large rewrite of SoftAE and combined all platforms to one engine. Sinks are available for all platforms.
*[[forum:128298|Linux AE forum thread]]
ActiveAE uses an active state machine pattern, with a separate high priority sink thread, that cares for underruns. ActiveAE is completely build upon ffmpeg, which is used for resampling, channel mapping and decoding. High performance SSE algorithms - already existent in the AEUtils - were fixed up and are used to do the final conversion into formats the sinks can accept. ActiveAE uses the ''float'' format internally and it is working bit-exact.
*[https://github.com/gnif/xbmc/tree/AE GitHub Development Branch (outside master)]


==See also==
A new feature is the upmix via AC3 transcoding support. On optical devices where only 2 pcm channels are available, we can now upmix to 5.1 by transcoding to ac3.
*[[Windows audio APIs]]
Another new feature is the PulseAudio sink for ActiveAE, which was merged into XBMC mainline on January 9th 2014 and enables Linux desktop users to use the PulseAudio system instead of ALSA, which was an often requested feature. See [[PulseAudio]]


ActiveAE has three build-in profiles: Best Match, Optimized and Fixed.
* ''Fixed'' takes care that all audio you will play is play in the very same data format. Your receiver does not need to switch modes.
* ''Best Match'' is what previously existed as the "audiophile" mode. Whenever a new video or music playback starts, the audio engine will select the best sink for that stream. By design ''Best Match'' and ''gapless'' playback are not compatible. If you rely on ''gapless'' playback, consider using ''Optimized'' instead.
* ''Optimized'' is something special, as it tries to reduce the reopening of sinks a lot. One example is live-TV where it switches between 5.1 to 2.0 during commercials. In order to  not open the device anew and loosing some (milliseconds of) audio, the 2.0 commercials are played with the already open 5.1 sink by muting the non existent channels.
The main developers of ActiveAE are [[User:Fernetmenta|Fernetmenta]] and [[User:Fritsch|Fritsch]].
{{frodo updated}}


[[Category:XBMC Manual]]
[[Category:Audio]]
[[Category:Development]]
[[Category:Development]]

Latest revision as of 05:10, 4 August 2020

Home icon grey.png   ▶ Development
▶ Audio		 ▶ AudioEngine

AudioEngine or (AE) refers to XBMC's new audio system.

Features

AudioEngine replaces SDL and brings some of the external dependencies into XBMC, and wraps up all the different media types for mixing, samplerate conversion, format conversion, encoding, upmix, downmix, etc.

Features of AE include
  • Support for DTS-HD MA / Dolby TrueHD Bluray formats
  • Support for 24-bit and floating-point audio at up to 384,000hz
  • Mixing of all streams including GUI sounds even when transcoding audio
  • Start-up enumeration of hardware audio devices and their capabilities with log output
  • Bitstreaming support in PAPlayer (XBMC's music player)
  • Upmixing of stereo to full channel layout
  • Tighter syncing of A/V streams
  • Floating-point processing of audio
  • 24-bit and floating-point decoding/handling of mp3
  • Full support for ReplayGain
  • Built-in sample-rate conversion and transcoding

It's still early days for AE. Bugs will be found, and new and exciting features added.

Settings

Audio settings can be found in the GUI at

Settings -> System -> Audio output


Supported Audio Formats for Passthrough

A summary of some of the supported formats within the AudioEngine

Audio Codec Audio Source XBMC Passthrough Setting
HD DVD Blu-ray Disc DVD-Video DVD-Audio
Channels (max) Max bit rate Sample rate (max) Channels (max) Max bit rate Sample rate (max) Channels (max) Max bit rate Sample rate (max) Channels (max) Max bit rate Sample rate (max)
Dolby Digital (AC-3) 5.1 504 kbit/s 48 kHz / 16 bit 5.1 640 kbit/s 48 kHz / 16 bit 5.1 448 kbit/s 48 kHz / 16 bit 5.1 448 kbit/s 48 kHz / 16 bit Dolby Digital (AC3) capable receiver
Dolby Digital Plus (E-AC-3) 7.1 3 Mbit/s 48 kHz / 24 bit 7.1 1.7 Mbit/s 48 kHz / 24 bit N/A
DTS 5.1 (Core) 1536 kbit/s 48 kHz / 24 bit 5.1 (Core) 1536 kbit/s 48 kHz / 24 bit 6.1 768 kbit/s 48 kHz / 16 bit N/A DTS capable receiver
DTS 24/96 N/A 5.1 1536 kbit/s 96 kHz / 24-bit 5.1 1536 kbit/s 96 kHz / 24-bit
Linear PCM (LPCM) 7.1 27 Mbit/s 192 kHz / 24 bit 8.1 27 Mbit/s 192 kHz / 24 bit 5.1 6.1 Mbit/s 48 kHz / 16 bit 5.1 6.1 Mbit/s 96 kHz / 24 bit MultiChannel LPCM capable receiver
Dolby TrueHD 7.1 18 Mbit/s 192 kHz / 24 bit 7.1 18 Mbit/s 192 kHz / 24 bit N/A TrueHD capable receiver
DTS-HD High Resolution Audio (HRA) 7.1 6 Mbit/s 96 kHz / 24 bit 7.1 6 Mbit/s 96 kHz / 24 bit N/A DTS-HD capable receiver
DTS-HD Master Audio (MA) 5.1 18 Mbit/s 192 kHz / 24 bit 5.1 18 Mbit/s 192 kHz / 24 bit N/A
7.1 18 Mbit/s 96 kHz / 24 bit 7.1 18 Mbit/s 96 kHz / 24 bit N/A

Test audio files

Below You can find a excellent range of flac test audio files stereo/multichannel and varied sample/bit rates and quality.

Click here to download flac test files

Click here to download wma test files

Click here to download various audio system test files


History and Team

AudioEngine, AE for short was two-year project spear-headed by Gnif which was released in v12 (Frodo), and was first merged with master for user testing as of May 15th, 2012.

Why write a new audio subsystem?

It's been an accepted fact that the existing audio code was little-touched since the early days of XBMC, and was limited by the 16-bit architecture of the original Xbox and codecs available at the time. Dolby AC3 and mp3 (or earlier formats!) ruled the media codec world. Over time HTPC's became more mainstream, more powerful and better connected. Analog connections gave way to optical SPDIF connections, which in turn were replaced with HDMI. Processors, GPU's and media formats evolved at a steady pace.

With the growth of the HTPC and new formats like those made available with Bluray technology, the audio subsystem was under scrutiny as an area for improvement. Higher definition audio like multichannel FLAC was becoming a preferred standard for those demanding higher quality audio media. It was time for an update, and what an update!

Early efforts at patching fixes and even an initial attempt at a completely new system fell by the wayside. The scope of the required changes and the complexity of the API made it a daunting task, especially for volunteer programmers working in their spare time. This was compounded by the fact that XBMC runs on a wide range of hardware and operating systems. Most of the developers focus on specific platforms or subsystems within the whole of XBMC. Any new system had to be platform-agnostic, cohesive and flexible.

In time, it became obvious the project was going to require a full re-write and replacement of the audio engine. Furthermore, XBMC's base of hardware and OS platforms continued to grow. The detailed specifications for the new audio formats were unknown, and of course the master code for XBMC was ever-changing.

Three years of work

In November of 2009 Gnif decided to bite the proverbial bullet, and after extensive consultation with the team finalized the API or structure which was to become AE. Drawing in other developers as required, the massive project slowly took shape, and reached the ready-point for user tests a year later. The forum thread for those hardy beta-testers (thank you!) reached over 1,200 posts, and slowly but surely features were added and debugged, and system stability grew.

Over the next two years, thanks to the determination of Gnif the core engines, decoders, encoders and utilities that make up AudioEngine became a reality, and other developers began to contribute to the core and especially the platform-specific sinks or output stages. Among those contributing were Gimli, Fneufneu, Memphiz, Dddamian, Anssi and others.

There was a goal to have the new audio system ready for Eden 11.0, but there was just too much left to do. Many users were eagerly looking forward to it's inclusion, but stable releases must continue, and AE wasn't ready when the Eden feature-freeze went into effect. During this time the AE code-base was solidified, bugs tracked and squashed, features added and testing increased.

Finally, on May 15th 2012, AudioEngine was merged to master. Weighing in at over 22,000 lines of code, it represents one of the single biggest code-merges ever for XBMC. Now for the first time it is readily accessible for all the development team (and users!) to see, test and improve within the greater context of XBMC's master branch.

ActiveAE

ActiveAE was a large rewrite of SoftAE and combined all platforms to one engine. Sinks are available for all platforms. ActiveAE uses an active state machine pattern, with a separate high priority sink thread, that cares for underruns. ActiveAE is completely build upon ffmpeg, which is used for resampling, channel mapping and decoding. High performance SSE algorithms - already existent in the AEUtils - were fixed up and are used to do the final conversion into formats the sinks can accept. ActiveAE uses the float format internally and it is working bit-exact.

A new feature is the upmix via AC3 transcoding support. On optical devices where only 2 pcm channels are available, we can now upmix to 5.1 by transcoding to ac3. Another new feature is the PulseAudio sink for ActiveAE, which was merged into XBMC mainline on January 9th 2014 and enables Linux desktop users to use the PulseAudio system instead of ALSA, which was an often requested feature. See PulseAudio

ActiveAE has three build-in profiles: Best Match, Optimized and Fixed.

  • Fixed takes care that all audio you will play is play in the very same data format. Your receiver does not need to switch modes.
  • Best Match is what previously existed as the "audiophile" mode. Whenever a new video or music playback starts, the audio engine will select the best sink for that stream. By design Best Match and gapless playback are not compatible. If you rely on gapless playback, consider using Optimized instead.
  • Optimized is something special, as it tries to reduce the reopening of sinks a lot. One example is live-TV where it switches between 5.1 to 2.0 during commercials. In order to not open the device anew and loosing some (milliseconds of) audio, the 2.0 commercials are played with the already open 5.1 sink by muting the non existent channels.

The main developers of ActiveAE are Fernetmenta and Fritsch.

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