= Upmpdcli
== Introduction
Upmpdcli is primarily an UPnP Renderer front-end to the MPD music player.
It has a number of additional or alternative functions.
The xref:UPNP[next section] explains the network audio terms (UPnP, Media
Renderer, etc.) if your knowledge needs a little brushing up. Else, you can
jump to the xref:UPMPDCLI-OVERVIEW[upmpdcli overview] section.
Do not scrap your old amp yet, with 100 Euros (a Raspberry Pi and a high
quality DAC I2S daugtherboard) you can transform it into a state of the art
network streamer (my main one is 25 years old).
=== Security
WARNING: The UPnP protocols have no security
provisions. Upmpdcli is not audited for security issues, and, as far as I
know, it is full of exploitable bugs. Do not run it on an Internet-facing
host.
[[UPNP]]
== UPnP and all that
=== UPnP AV
UPnP is a family of network protocols, designed for easily connecting
_stuff_ in home networks (mostly). Its name ("Universal Plug and Play") was
chosen because little or no configuration is needed for the different
elements to discover each other and play together.
The UPnP audio/video section (UPnP AV) implements a way for data stored on
a network host (PC, NAS, etc.) to be displayed on another one (TV, audio
streamer, etc.).
Generally, there are four building blocks in a network audio solution:
- An audio File/Data server stores the (bulky) audio data and makes it
available to clients using an appropriate protocol (NFS, SMB, HTTP,
etc. depending on client).
- The directory/tags manager extracts audio tags from the files (usually
accessing them directly or through a network file sharing protocol), and
builds a database used for searching or browsing the collection.
- Audio players (renderers) take encoded audio data and actually make
sound, using some kind of DAC (Digital Analog Conversion) device, such as
an internal or USB sound card.
- The user interface is a remote control which sits in your hand (or it's
the PC in front of you). You use the application which runs on it to
choose songs from the database and control the playback. It interacts
both with the tags database and player parts (usually not with the file
server, except maybe to fetch cover art).
.Network Audio
image::pics/netaudio.png["Network Audio Elements"]
In the UPnP world:
- The tags manager is named Media Server (more precisely, the Content
Directory service inside the Media Server device). Data is usually
stored on the Media Server, but it could also live elsewhere. Data
access is almost always performed through HTTP.
- The player is named Media Renderer. It usually does not implement much
user interface.
- The remote control is named Control Point
The good people who specified UPnP AV got something wrong: the playlist
is owned by the Control Point, not by the Renderer. This means that the
Renderer will not play the next track if the Control Point goes to sleep,
and that havoc is almost guaranteed if several Control Points try to share
a Renderer. This is the main reason for using OpenHome (see <<OPENHOME,next>>).
[[OPENHOME]]
=== OpenHome
The link:http://wiki.openhome.org/wiki/OhMediaDevelopers[OpenHome] family
of open protocols were designed by link:http://www.linn.co.uk/[Linn] to correct
the weaknesses in UPnP AV. They implement extended services over the base
UPnP mechanisms.
Principally, the OpenHome playlist lives on the Renderer. It will continue
playing if the Control Points goes to sleep, and it can be shared. This is
a compelling advantage and most well-known Control Points (e.g. BubbleUPnP,
Kazoo, PlugPlayer...) support OpenHome.
Beyond this, OpenHome also defines additional services, for example for
accessing Internet radios. The different possible origins of audio data
inside an OpenHome Renderer are named _Sources_, e.g. Radio Source,
Playlist Source. Sources are switchable from any Control Point supporting
OpenHome.
OpenHome Sources are designated by a type and name, and a Renderer can have
any number of them (for example, Upmpdcli uses additional sources to
control its Sender mode).
=== Songcast
link:http://oss.linn.co.uk/trac/wiki/Songcast[Songcast] is an open protocol
designed by Linn for real-time network audio. Its only relationship
with UPnP is that UPnP services are used to control the
connections. Songcast allows playing the same audio on multiple players,
with almost perfect synchronization, or capturing audio on a computer to
play it on another system.
The protocols links two types of entities:
- A Songcast Sender generates an audio stream.
- One or several Songcast Receivers receive and play the stream.
Linn supplies free audio capture drivers functionning as Songcast Senders,
for MS-Windows and Mac OS X. This enables playing the audio of *any*
application (Windows Media Player, Spotify, Tidal, etc.) onto one or
several Songcast Receivers, without any need for the applications to know
about Songcast.
=== Gapless ?
This is a relatively small issue, but people are very sensitive to it, it
is important from some music pieces (Goldberg variations with gaps: not
nice) and you will hear about it all the time if you read forums, so, a
quick explanation follows.
Some music tracks need to flow into each other when played consecutively,
for example tracks on some live albums (the background noise from the
audience never stops), or some classical music pieces.
When playing from separate audio files, it is not trivial for a renderer to
ensure a seamless flow: the audio hardware has an input pipe which must be
kept full at all times, else it will stop, and a period of silence will
ensue: not gapless !
To avoid this, the renderer has to know in advance which file it will
process after the current one, to be able to begin filling the audio pipe
with data from the next track before it empties at the end of the current
one.
There are two ways that this can be achieved: either the renderer is also
in charge of the play queue, so it knows the whole sequence all the time
(e.g. MPD, OpenHome, ���), or the controller indicates the next track to the
renderer before the current track finishes (e.g. UPnP SetNextTransportURI).
[[UPMPDCLI-OVERVIEW]]
== Upmpdcli overview
Upmpdcli is primarily a UPnP Media Renderer frontend, using a slave MPD to
actually process the audio data. It supports UPnP gapless track transitions
and the OpenHome ohMedia services (including a Radio service to listen to
Internet streams).
.The Grand Upmpdcli Scheme of Things
image::pics/upmpdcli.png["The Grand Scheme of Things"]
Additionally:
- Upmpdcli implements control functions for the Linn Songcast protocol,
allowing the local machine to behave as a Songcast Receiver or Sender (with
help from the closely related *sc2mpd* package, for processing the audio
streams).
- Upmpdcli provides a Media Server interface, currently used for accessing
external streaming services (Qobuz, Tidal, Google Music). A local Media
Server is in development, the motivation being that I see none which is
both open-source and really satisfying (MinimServer is great but not
open-source).
Upmpdcli can be installed on most Linux systems. It is frequently used on
small single board computers like the Raspberry Pi. As far as I know, all
audio-oriented distributions currently use it as their UPnP Media Renderer
interface, and it is also present in a number of commercial devices.
Upmpdcli is mostly configured through values set in a configuration file
but, for basic operation without a configuration file, a few of the main
parameters can be set on the
xref:COMMAND-ENVIRON[command line or in the environment].
Most parameters can only be set in the configuration file, which is
designated with the +-c+ command line option. The usual location is
+/etc/upmpdcli.conf+
The configuration file has a simple `name = value` format, and is fully
described in the <<UPMPDCLI-CONFIGURATION,configuration reference section>>.
upmpdcli has many configuration parameters, which may make the
configuration intimidating. However, most parameters only relate to one
function of the program and they are grouped in sections, many of which
are probably not relevant to you. In each section, the most important
parameters are presented first, and you probably will never need to bother
with the bottom of the list.
The <<UPMPDCLI-CONFIG-GUI,upmpdcli-config graphical tool�� can help you edit
the configuration file, it can present the same information as this manual,
directly linked with the controls used to modify the parameters.
[[UPMPDCLI-RENDERER]]
== Upmpdcli Media Renderer
//////////////////////////////////////
// Note about configuration section refs: only the first parameter in a
// subsection can be referenced, and it references the whole
// subsection. Hence refs like <<mpdhost,+mpdport+>>, which are not typos
/////////////////////////////////////
This section goes in a little more detail about miscellaneous aspects of
the Media Renderer, and describe a few of the most used configuration
parameters. See the <<UPMPDCLI-CONFIGURATION,configuration reference section>>
for more details (I would very much like to link each parameter to its
definition but Asciidoc won't let me do it, so they link to the top of the
appropriate section.).
If several instances of *upmpdcli* run on the same network, you will want
to give them distinct names. The name which is displayed by most Control
Points can be set with the <<friendlyname,+friendlyname+>> configuration
parameter. Some Linn Control Points (e.g. Kazoo) use another value, set
with <<ohproductroom,+ohproductroom+>>.
Upmpdcli usually controls the MPD instance running on the same
host. However, there may be reasons to do otherwise, and the host name and
port where mpd should be reached can be set with <<mpdhost,+mpdhost+>>,
and <<mpdhost,+mpdport+>>.
The Upmpdcli Media Renderer has two active interfaces by default: UPnP AV
and OpenHome. Only OpenHome Control Points can share the renderer. If you
use an UPnP AV Control Point, it must be the only one. This is not
enforced, and misuse will result in miscellaneous weirdnesses. In some
special situations, it may be useful to limit the interface to UPnP AV or
OpenHome only (or disable both), which can be done with the
<<friendlyname,+openhome+>> and <<friendlyname,+upnpav+>> parameters.
[[UPMPDCLI-RENDERER-FORMATS]]
=== Audio formats
Upmpdcli can accept most audio formats supported by MPD, meaning about
anything, including DSD.
Upmpdcli normally checks that the format of a resource to be played is
compatible with what it thinks MPD can do. This check is sometimes
pessimistic and can be disabled by setting
<<friendlyname,+checkcontentformat+>> to 0.
You should know that MPD has difficulties with some formats _when accessed
through HTTP_ which is how the Media Server transfers the data.
Specifically, WAV and AIFF files, especially with samples wider than 16
bits are a frequent source of trouble (because they are little used and
little tested for streaming). Support will vary depending on the MPD
versions and exactly what input plugins are configured (among *ffmpeg*,
*libaudiofile* and *libsndfile*). Often, the same files play just fine
locally, it's the combination of HTTP access and file format which causes
problems.
Raw PCM streams are another special case. The reason is that these streams
do not, by definition, carry metadata to define the exact format (sample
rate, bits per sample, number of channels, byte order). *upmpdcli* has no
way to transfer these parameters to *MPD* (this is a limitation of the
client protocol). The parameters can be transferred from the Media Server
to the player along with the MIME type though. In consequence, only recent
versions of Upmpdcli and MPD (0.20 and later) do support audio/L16, but
not with any Media Server (it must output the audio formats
parameters with the MIME type). See this issue for more details:
https://www.lesbonscomptes.com/upmpdcli/github-issues/upmpdcli-html/issue-36.html
In general, there are few reasons to use these linear formats, when FLAC
will produce exactly the same bits, with less network load (which largely
compensates the small additional CPU load).
There are situations where the linear formats are needed though, and where
it may be necessary to use the right MPD and plugins versions.
[[radio-definitions]]
=== Radio station definitions
Upmpdcli versions after 0.13 implement an OpenHome Radio service
which allows selecting and listening to internet radio stations.
This facility uses Python 2.x, which must be available on the system for
the radio links to work.
Radio stations can be defined in the configuration (at the end because of
the use of section indicators), or in in a separate file by setting the
<<ohproductroom,+radiolist+>> parameter in the main configuration.
Radio channels can be accessed by selecting the _Radio_ Source from an
OpenHome Control Point.
Example entry:
----
[radio Radio Teddy]
url = http://opml.radiotime.com/Tune.ashx?id=s80044
artUrl = http://cdn-radiotime-logos.tunein.com/s80044q.png
artScript = /path/to/some/script
metaScript = /path/to/some/other/script
----
The section name must begin with +radio+, the rest will be displayed as the
station name. The section has several possible entries. Only +url+ is
mandatory, it points to the playlist or stream.
If set, +artUrl+ is a link to a static icon for the radio (displayed as
album art).
If set, +artScript+ is the path to an executable script which can retrieve
the image URL for the currently playing title.
Some radios (e.g. link:https://www.radioparadise.com/rp_2.php?#[Radio
Paradise]) publish the album art for the currently playing title. The
details vary. The +artScript+ parameter, if set, should point to an
executable script which prints this dynamic art Uri to stdout. The image
will supercede the radio logo, to be displayed by control points. Beware
that the path to the script must be accessible by the _upmpdcli_ user,
which may not be the case for your home. +/usr/local/bin+ is your
friend. As a very rough example here follows a command which would retrieve
the Radio Paradise URI (as long as they don't change their format, a proper
approach would use an XML parser of course):
curl --max-time 5 -s http://radioparadise.com/xml/now.xml | \
grep '<coverart>' | sed -e 's/<coverart>//' -e 's!</coverart>!!'
Also note that upmpdcli does not set a timeout for the +artScript+
execution. A reasonable value should be used inside the script, to avoid
freezing upmpdcli forever.
If set, +metaScript+ is the path to an executable script which can retrieve
the metadata (possibly including art Url) for the currently playing title.
The script should output the metadata in JSON format. Example output
(the newlines and blank space are just here for readability):
----
{
"title":"The title of the current track",
"artist":"The artist playing",
"artUrl":"https://www.somesite.com/path/to/image.jpg",
"reload":103
}
----
The +reload+ value gives the number of seconds after which the script
should be re-executed (the clever radio sets this to the remaining song
time). By default, the script is executed every 10 S.
Complete exemple with metadata script:
----
[radio FIP (Paris)]
url = http://direct.fipradio.fr/live/fip-midfi.mp3
artUrl = http://www.fipradio.fr/sites/default/files/fip-quadri-filet.png
metaScript = /usr/local/bin/fip-paris-meta.rb
----
And the script (this one in Ruby, thanks to
link:https://github.com/distler[Jacques Distler]):
----
#!/usr/bin/ruby
require 'net/http'
require 'json'
uri = URI('http://www.fipradio.fr/livemeta/7')
response = Net::HTTP.get(uri)
songs = JSON.parse(response)['steps'].values
now = Time.now
songs.each do |song|
song_end = Time.at(song['end'])
if (song['embedType'] == 'song' && song_end >= now && Time.at(song['start']) <= now)
title = song['title'] ? song['title'] : ''
artist = song['performers'] ? song['performers'] : song['authors']
metadata = {'title' => title.split.collect{|s| s.capitalize}.join(' '),
'artist' => artist.split.collect{|s| s.capitalize}.join(' '),
'artUrl' => song['visual'],
'reload' => (song_end - now + 1).to_i}
puts JSON.generate(metadata)
break
end
end
----
[[UPMPDCLI-SONGCAST]]
== Upmpdcli and Songcast
Upmpdcli implements the Receiver UPnP service, and uses an auxiliary
process (*sc2mpd*) for transporting the audio data. *sc2mpd* is based
on the sample program which comes with the Linn Songcast
OpenHome open source implementation
Upmpdcli can also manage a Sender subsystem, which is implemented by using
a separate *mpd* instance sending audio to an *mpd2sc* command (part of the
*sc2mpd* package). The latter is a modified version of the OpenHome
WavSender sample program. This allows playing the usual Upmpdcli playlist
or a a radio channel on several synchronized players, but also doing the
same thing with a captured analog source (e.g. *arecord* output).
NOTE: You should know that it is possible to control the Songcast Sender
from another local network PC to snoop on what you are listening (Radio or
Playlist). This is detectable from the Renderer state, but not obvious. In
any case, the playlist itself is public (there are no privacy provisions in
UPnP), so this is probably not a major additional issue. The system will
not capture anything besides what *mpd*, or an explicitely setup additional
source are playing (e.g. Skype phone conversations are out of reach).
[[UPMPDCLI-SONGCAST-COMPAT]]
=== Upmpdcli Songcast Control Point compatibility
Upmpdcli Senders and Receivers can be mixed with Linn ones and controlled
from Upplay or Bubble DS (an maybe other control points).
Neither Linn nor upmpdcli receivers can be linked to an upmpdcli Sender using
Linn Kazoo (tested with release 4.11.226), the reason is unknown.
Upmpdcli Receivers before release 1.2.14 are not visible in Linn
Kazoo. Later versions can be linked, and stream, from a Linn Sender.
Linn Kazoo can control the playlist in an upmpdcli instance which has been
put in Sender mode by another CP (i.e. currently using the PL-To-Sender
source). The Lumin IOS app will reset the Source to Playlist when
connecting, so it is unusable in this context.
[[UPMPDCLI-RECEIVER]]
=== Upmpdcli Songcast Receiver
*sc2mpd* can play the *Songcast* audio stream in two modes:
- By directly using the *alsa* audio driver.
- By using *mpd* to play the stream offered from a local HTTP interface
(hence the *sc2mpd* name)
.Upmpdcli Receiver in `alsa` and `mpd` modes
[options="header"]
|=============
|`alsa`|`mpd`
|image:pics/upmpdcli-receiver-alsa.png[Upmpdcli Receiver, alsa mode]|image:pics/upmpdcli-receiver-mpd.png[Upmpdcli Receiver, mpd mode]
|=============
What approach is used is decided by the <<sclogfilename,+scplaymethod+>>
configuration parameter, which can be set to _mpd_ or _alsa_.
The _mpd_ mode is the default, because it needs no configuration, but there
are *multiple* problems with it. If you go the _alsa_ route,
you will need to set <<sclogfilename, +scalsadevice+>> in the
configuration, but you probably had to set it in the MPD configuration too,
so this may not be too much of an issue.
NOTE: when using the _alsa_ approach, *sc2mpd* will open the audio driver
directly. The *sc2mpd* process is started by *upmpdcli*, which normally
runs with user id _upmpdcli_. A frequent cause preventing the Receiver from
working is that the driver open fails because _upmpdcli_ user has no
permission to access it. One solution is to create an _audio_ group (if it
does not exist), make the devices writable by _audio_, and add _upmpdcli_
(and others) to the _audio_ group.
When using *mpd*, more bufferisation occurs and there may be a significant
delay (up to around 10 S) between the time when Songcast is activated
and the time sound appears.
NOTE: When using _mpd_, from a Mac (24 bits audio) you need an
appropriately configured and recent MPD version (usually configured with
`--disable-audiofile`), else you risk producing high volume noise. As
Debian and Ubuntu tend to lag quite bit on MPD progresses, I have set up
link:downloads.html#mpd[backport repositories] for appropriately configured
recent mpd versions, for Ubuntu, Debian i386/amd64 and
Raspbian. Unfortunately, not only the MPD version is significant, there are
sometimes also problems in the input plugins libraries.
Given the bufferisation and delay control issues when going through MPD,
only the _alsa_ method is usable in multi-room configurations. Even with a
single player, the _mpd_ method will experience skips from time to
time. The reasons are explained in the xref:UPMPDCLI-MULTIROOM-SYNC[multiroom
synchronization section].
The following steps are taken for establishing a Songcast connection:
- If *upmpdcli* finds an executable *sc2mpd* command in the PATH when
starting up, it advertises a Receiver service.
- The *Songcast* application on the desktop finds out about the
Receiver through the normal UPnP mechanisms and can be instructed to
use it. It then tells the Receiver in *upmpdcli* to start playing.
- *upmdpcli* starts the *sc2mpd* process, which gets ready to receive data
through Songcast, and either play it directly or make it available
through HTTP.
- If the _`mpd`_ method is in use, *upmpdcli* instructs *mpd* to play the
URL for the *sc2mpd* output.
WARNING: There is *no software volume control* for the *upmpdcli* Songcast
Receivers for now: use either a local mixer or the little round things on
the pre-amps. Set the volume low when experimenting !
NOTE: Songcast can use IP multicast for lower load on the network when
playing on several hosts. Unfortunately, multicast and WIFI don't mix well
in many cases. If you have wireless Receivers experiencing sound drop
issues, try selecting unicast in the Songcast advanced configuration panel
on the desktop.
[[UPMPDCLI-SENDER]]
=== Upmpdcli Songcast Sender
Upmpdcli Sender mode allows you to broadcast the Playlist or Radio source
(or the output of any process which can write to a Fifo, e.g. *arecord*) to
other Songcast Receivers. The local *upmpdcli* plays through its Receiver
too, in order to achieve good synchronisation. Unlike the Songcast
applications on Windows or Mac, the audio is not captured from the driver,
so that you won't be able to cast other applications transparently (but
there are specific workarounds).
You can set *umpdcli* in Sender mode from an OpenHome Control Point, by
selecting the Source of type `Playlist`, name `PL-to-Songcast` or type
`Radio`, name `RD-to-Songcast` (and others if using the extension
mechanism). With
link:http://www.lesbonscomptes.com/upplay/index.html[upplay], for example,
you can select the source from the `File`->`Select Source` menu entry.
The *sc2mpd* configuration *must* be set with +scplaymethod = alsa+ for the
`XX-to-Songcast` sources to appear. See the
xref:sclogfilename[configuration section], and the
xref:UPMPDCLI-MULTIROOM-SYNC[section about synchronisation].
When entering Sender mode, *upmpdcli* will start an auxiliary MPD process
(after stopping the main one), configured to send audio to the *mpd2sc*
OpenHome Sender process. It will then also start its own Songcast
Receiver mode, transfer the playlist, stop the main MPD and start the
auxiliary one...
The resulting state is that the *upmpdcli* instance can be managed in
Playlist mode from the Control Point. The audio is played locally through
the Songcast Receiver. Other Receivers can be connected and will play in
good synchronization.
image::pics/upmpdcli-sender-receiver.png["Sender/Receiver mode"]
This looks complicated, but in practise, starting the mode and connecting
other Receivers from the *upplay* control panel is quite straightforward.
[[UPMPDCLI-SENDER-EXTSOURCES]]
==== Managing external sources
In the Sender modes described above, *upmpdcli* (or rather its slave *mpd*
process) is the source of the audio stream. The *mpd2sc* program (which is
just a slight modification of a Linn sample) reads the *mpd* output from
a FIFO and sends it to Songcast Receivers (including the local one).
There is nothing special with the *mpd* output (it is just PCM audio), and
it is also possible to set things up for *mpd2sc* to read from another
source.
This is made reasonably easy because the pipe is actually built by
a script (the default one is named 'scmakempdsender'), and *upmpdcli* has
built-in functionality for choosing different ones (creating OpenHome
sources for each script it finds in a specific directory). There is a
sample script in the distribution, which itself is flexible enough to allow
connecting several inputs without programming (anything *arecord* can read).
Still the details are a bit too much involved for the main body of the
manual, so I have moved them to an xref:SENDER-EXTSOURCES[annex].
[[UPMPDCLI-MULTIROOM]]
=== Songcast multiroom configurations and synchronization issues
Multiple Songcast Receivers can connect to the same Sender, for
synchronized playing of a the same audio stream.
The Mac and Windows Songcast applications only let you activate one Receiver.
The easiest way to manage multiple connections is to use an appropriate
control point, such as Upplay on Linux and Windows, BubbleDS on Android, or
Linn Kazoo (multiple platforms).
For the record, the *upmpdcli* package also includes the *scctl* command
line utility, which can list the state of the local Songcast Receivers,
make a Receiver play from the same URI as another one (for building
multi-room groups), or return a Media Renderer from Receiver to normal
operation. There is also a xref:SCWEB[small Web application] which can be
accessed from a desktop web browser to control the groups. This has only
be tested with *upmpdcli* as Receiver implementation, but I'd guess that
there is a good chance it would work with others. Quite frankly, I think
that you'd better use the Control Point approaches if at all possible.
[[UPMPDCLI-MULTIROOM-SYNC]]
==== Synchronisation issues
The short version is: for good syncrhronization, all *sc2mpd* instances
must be configured to play directly to the audio driver with +scplaymethod
= alsa+. See the xref:sclogfilename[configuration section].
Longer version: *Songcast* is a real-time audio stream. As the Sender and
Receiver sample clocks (the 44.1 or 48 KHz clocks) are independant, audio
reproduction on the two systems will slowly drift. If nothing is done,
after a time, the Receiver will have to skip samples or add a period of
silence (depending if its clock is slower or faster), which is quite
audible and ennoying, and will happen "from time to time", depending of how
much the clocks differ.
The only way to control this is to adjust the rate of reproduction on the
Receiver, which can be done in two ways:
- *Linn* hardware uses timestamps embedded in the audio stream to adjust
their hardware sample clock.
- *sc2mpd* in _alsa_ mode uses sample rate conversion to adjust the stream.
- *sc2mpd* in _mpd_ mode can't do a thing about it.
This is not specific to *Songcast* of course, all real time audio network
transports have to do something similar (e.g. Roon does individual stream
adjustments on the server).
Independantly of the clock issue, all Receivers should use approximately
the same amount of buffering for the audio to be reasonably synchronous
(with no more shifts than moving around would produce anyway). This is
impossible to achieve when going through *mpd*, and the second reason why
*sc2mpd* must be set in _alsa_ mode for multiroom setups. In _mpd_ mode,
the Receivers can be out of sync by several seconds.
[[UPMPDCLI-MS-STR]]
== Support for Streaming Services
=== Streaming Services and UPnP
Streaming services like Qobuz or Tidal give access to a huge catalog of
music through a WEB interface (also usable by programs).
The only thing that they have in common with UPnP is that the actual audio
stream is obtained through HTTP. However, given their importance, they can
be accessed through many UPnP Control Points and Renderers.
There are three main ways to integrate the streaming services in an UPnP
framework, and knowing which way you are using will avoid confusion:
- The first approach is to have a UPnP Media Server act as a proxy for the
service: the catalog is browsed through a standard UPnP interface (the
Media Server translates this to the service API behind the scenes), and
the audio URIs are also accessed in an almost standard way (after a bit
of magic inside the Media Server). The one inconvenient of this approach
is that the special functions of the service (like managing the user
favourites lists) are mostly inaccessible. The advantage is that any
naive UPnP Control Point can access the streaming service. The Media
Server inside upmpdcli xref:UPMPDCLI-MS-STR-MS[implements this method].
- The second approach is to do everything inside the Control Point. The CP
uses the service API for browsing (and possibly do things like managing
favourites). The CP also mediates the HTTP access to the audio streams
(the URIs the CP sends to the Renderer point to itself, and it arranges
to forward the data from the service). This is implemented, for example,
by Bubble UPnP. The drawback of this approach is that the CP can't go to
sleep or out of reach, else the music will stop (maybe at the next track).
- The third approach is to distribute the function between CP and
Renderer. The Control Point performs the browsing and access to special
functions, and the Renderer knows how to access the service streams. This
is the OpenHome approach and can be considered the best of both worlds,
at the price of complexity and compatibility issues. This method is
implemented by the Kazoo and Lumin Control Points, and a number of
Renderers, the Linn and Lumin ones of course, but also,
xref:UPMPDCLI-MS-STR-CRED[lately by upmpdcli].
[[UPMPDCLI-MS-STR-MS]]
=== Accessing Streaming Services through the upmpdcli Media Server
The Media Server function in Upmpdcli (1.2.0 and later) gives access to
external streaming services: Qobuz, Tidal, and Google Music at the moment.
You will need a valid account on any service that you want to use.
When the function is activated, *upmpdcli* creates a separate auxiliary Media
Server, with the sole purpose of presenting the streaming server
catalog. You will see it appear on the network if streaming service
parameters are present in the configuration file. The Media Server name is
the +friendlyname+ for the Upmpdcli instance, with _-mediaserver_ appended.
Streaming is not limited to the local Upmpdcli Renderer, and the Media
Server will happily send music to other Renderers.
Two conditions must be true for the Media Server to appear with an entry
for a streaming service:
- The code for the service plugin must be installed. This comes generally
in a separate package (e.g _upmpdcli-qobuz_).
- The user variable for the service must be present in the configuration
file (e.g +qobuzuser+).
Some other parameters (e.g. a password) may be needed for the access to
work.
NOTE: The streaming services passwords are stored in the upmpdcli
configuration file ('/etc/upmpdcli.conf'). The installer does not
make this file r/w by owner only. This will be fixed, but for now, you
should probably do it after setting the password:
+chmod 600 /etc/upmpdcli.conf+ Actually, it would quite probably
be a good idea not to use the same account for your mail and music uses.
NOTE: I have no reason to believe that upmpdcli is technically mis-using
the streaming services in any way, but it is definitely not approved by any
of them, and you are using it under your own responsibility.
==== Notes on the Tidal interface
[NOTE]
===================================
There seems to be problems when streaming Tidal lossless/FLAC streams,
with the default MPD configuration. A preliminary and rather superficial
enquiry seems to indicate that this is caused by too much buffering by
MPD. Adding the following parameters to the MPD configuration file
(/etc/mpd.conf) reduces the pre-fetch period from 20 S to 10 S and seems to
fix the issues for me:
audio_buffer_size "2048"
buffer_before_play "20%"
====================================
The Tidal module code is is based on the
link:https://github.com/tamland/kodi-tidal[Kodi Tidal add-on] and the
link:https://github.com/tamland/python-tidal[Tidal API], by Thomas Amland
(also using other useful modules by Thomas). I was able to reuse most of
the Kodi code. The Tidal api module was recently updated and the login code
comes from link:https://github.com/arnesongit/kodi-tidal[this Git
repository]. The software is not officially supported by Tidal, and may
just stop to work one day...
It only works with a valid Tidal subscription.
The configuration parameters are described in the
<<tidaluser,configuration section>>
==== Notes on the Qobuz interface
This is based on the service API from the
link:https://github.com/tidalf/plugin.audio.qobuz[Kodi add-on], by Joachim
Basmaison and Cyril Leclerc, with the upper-level code adapted from the
Tidal add-on. The WEB API is not officially supported by Qobuz, and may
just stop to work one day.
NOTE: the Qobuz search does not allow searching a specific field (like the
artist name or song title). All objects matching a query in any field are
returned. This means that, e.g., the field choice of upplay search is
ignored.
You need a valid Qobuz subscription.
The configuration parameters are described in the
<<qobuzuser,configuration section>>
[[upmpdcli.googlemusicnotes]]
==== Notes on the Google Music interface
This is based on the
link:https://github.com/simon-weber/gmusicapi[gmusicapi] Python package by
Simon Weber, with upper-level code from the Tidal Kodi add-on. As for the
other services, the API used is not officially supported and may stop to
work one day.
This requires the installation of the external *gmusicapi* Python
package.
link:http://unofficial-google-music-api.readthedocs.io/en/latest/usage.html#usage[See the installation notes here].
NOTE: gmusicapi needs Python 2.7.9 or better (e.g. the standard Python
version on Ubuntu Trusty is too old). Older Python versions *will* crash.
You will need a valid subscription for most functions.
I'm a little lost in the different google authentication/sign-in methods,
but if you are using two way authentication, there is apparently
link:https://www.lesbonscomptes.com/upmpdcli/github-issues/upmpdcli-html/issue-87.html[a
way to make things work, using an app password].
The configuration parameters are described in the
<<gmusicuser,configuration section>>
[[UPMPDCLI-MS-STR-CRED]]
=== Accessing the streaming services with OpenHome from Kazoo or Lumin
This only works for Qobuz and Tidal. The corresponding media server module
must be installed, but no other configuration should be needed on the
renderer. The media service icons will appear in the CP interface, and the
service will be accessible after entering the login and password.
NOTE: the user name and password will be stored on the renderer in an
insecure way, meaning that if someone steals the machine or obtains root
access, there is nothing to prevent them from getting the credentials.
Of course Kazoo or Lumin can also access the services through the media
server interface (after configuring upmpdcli, see the
xref:UPMPDCLI-MS-STR-MS[previous section]).
[[UPRCL]]
== Upmpdcli local Media Server: uprcl
The current (2017-04) upmpdcli code base includes a Media Server function
for local music files, analog to MinimServer or ReadyMedia/MiniDLNA. The
plugin module is named uprcl.
Why yet another Media Server ? MinimServer is great, and free, but not
open-source. ReadyMedia is nice too, but audio file format support is
incomplete (there was a patch for DSD but it was never merged apparently),
I've always found it a bit clunky (for example: no incremental updates),
and development does not seem very active.
The new upmpdcli Media Server is at most beta quality. It probably has even
less format support than MiniDLNA... But it's written in Python, and I have
good hope that it can evolve faster.
Some features:
- Mostly written in Python, except for the pieces shared with the streaming
plugins: UPnP interface proper, and plugin management, which are C++, but
should not need a lot of changes.
- Tries to mimick the MinimServer tree view, which I find quite nice. We're
not quite there yet, many functions and niceties, and the customization
capability are missing.
- Uses Recoll and python-recoll (hence the uprcl name) for harvesting the
metadata and searching. Recoll already had almost everything needed in
this area, no development needed. It can perform incremental updates and
file system monitoring.
- Uses Python sqlite3 (on a memory DB) for the tags tree.
Installation and configuration: have a look at the
xref:uprcluser[configuration variables]
NOTE: 'python-mutagen' which is optional for default Recoll installations is
required for uprcl (this is for the case where you install by hand, the
package takes care of it).
[[UPRCL-SEARCH]]
=== Upmpdcli/Uprcl searches
The UPnP Media Server search function is based on a specific query
language. This language is quite verbose, and most control points will not
let you access it directly. Instead, they will usually provide a generic
entry field in which you enter search terms. Behind the scenes, they
generate an UPnP search language string. This could be for example
something like: `upnp:class = "object.item.audioItem" and dc:title
contains "heaven"`
If it supports search at all, the Media Server will then interpret the
query string and return the results.
If the Media Server is Upmpdcli/Uprcl, there is another step: the UPnP
query string is translated into a Recoll one and Recoll is called to
perform the actual search. There is no way to directly enter a Recoll
search through the control point. However, two important Recoll
capabilities should still be visible through the layers:
.Stemming
Stemming is the capability to expand a search to the common derivatives of
a word. For example, a search for `floor` would be expanded to also look
for `floors`, `flooring`, `floored`, etc. By default, stemming is enabled
for Uprcl search. It can be turned off for any term by capitalizing the
term (Entering `Stones` will only search for `stones`, not `stone` or
`stoned`). Uprcl/Recoll searches are case-insensitive apart from this usage
of capitalization.
.Phrase searches
By default, Uprcl/Recoll searches do not observe the order
of terms: `red house` will be matched by a search for `house red` (or
`houses red`). You can change this behaviour by quoting a sequence of
words. A search for `"red house"` will only look for a text containing the
words in order. This supposes that the Control Point does not change the
user entry, but this is the case for at least some of them. Stemming
expansion does not occur within phrase searches.
Other Recoll capabilities, such as proximity searches should also be
accessible, but probably less useful when searching music titles or artist
names.
[[UPMPDCLI-CONFIGURATION]]
== Upmpdcli configuration file reference
include::upmpdcli-config.txt[]
[[UPMPDCLI-PACKAGES]]
== Installation from packages
The link:https://www.lesbonscomptes.com/upmpdcli/downloads.html[upmpdcli
downloads page] has a number of pointers to binary packages for a number of
common distributions (Debian, Raspbian, Ubuntu, Fedora) and architectures
(ARM and x86).
[[UPMPDCLI-BUILDING]]
== Building from source
=== Building libupnpp and upmpdcli on Linux
For building from source, you will need a C\++ compiler with full
C++11 support, and the development packages for *libupnp* version 1.6,
*libcurl*, *libmpdclient*, and *libexpat*.
Also the Python modules for streaming service support use the
*python-requests* package, so you may need to install it (it is only needed
at run time). Also *gmusicapi* for Google Music.
If you are using the source from the git repository, you will also need the
*autoconf*, *automake*, *libtool* trio. Use the +autogen.sh+ script to set
things up.
The *libupnpp* library, which used to be part of *upmpdcli*, has been
separated, and you need to build it first.
So you need to either clone two git repositories:
https://opensourceprojects.eu/p/libupnpp/code and
https://opensourceprojects.eu/p/upmpdcli/code
or download the release tar files from the the
link:https://www.lesbonscomptes.com/upmpdcli/downloads.html[upmpdcli
download page]
Once the source is extracted, the procedure is standard and there are
currently no specific configure options:
# Only for git source
sh autogen.sh
./configure --prefix=/usr --sysconfdir=/etc
make
sudo make install
Which you should apply first to the *libupnpp* source, then to *upmpdcli*.
If you omit the `--sysconfdir=/etc` part, `upmpdcli.conf` will end up in
`/usr/etc/`, which is ok, but confusing, as package installers put it in
`/etc/`
==== Boot time startup
*upmpdcli* will try to change its `uid` to user `upmpdcli` if it is
started by root. It will refuse to run if the user does not exist.
If started by `root`, *upmpdcli* will also write its process id to
`/var/run/upmpdcli.pid`.
There are boot-time startup scripts in the `debian/` directory inside the
source tree (for Debian/Ubuntu/Mint/Raspbian etc.). There is also a systemd
service file under `systemd/` (for Fedora et al.).
The boot scripts are installed by the pre-built packages, so will just have
to edit the configuration file after installing them, all the rest should
just work.
=== Building libupnpp and upmpdcli on Mac OS X
I don't run Mac OS X and I can't support this directly. However a kind user
has provided a
link:https://opensourceprojects.eu/p/upmpdcli/tickets/3/[build recipe]
based on homebrew.
You will first need to apply the patches from
link:https://www.lesbonscomptes.com/upmpdcli/files/2017-12-upmpdcli-macos-build-patches.tgz[this
file].
Then:
----
brew install mpd
brew install autoconf
brew install automake
brew install libtool
brew install libupnp libmpdclient expat jsoncpp libmicrohttpd expat curl
brew install pkg-config
brew install expat
export PKG_CONFIG_PATH=/usr/local/opt/expat/lib/pkgconfig
configure --prefix=/usr
make
----
=== Building OpenHome and sc2mpd
There are two parts in building *sc2mpd*:
- Building the Openhome libraries
- Building *sc2mpd* proper
First download a
link:http://www.lesbonscomptes.com/upmpdcli/downloads.html[*sc2mpd*
release] or clone the *sc2mpd*
https://opensourceprojects.eu/p/sc2mpd/[Git repository].
==== Building the OpenHome libraries
Building the Openhome libraries is a bit of a black art for a number of
understandable reasons:
- There are no released distributions for the OpenHome libraries, but
only a number of git repositories for the different components. The state
of the repositories is not completely consistent at all times (there will
be moments when a component will not build with another).
- The OpenHome build system is very complicated because it works on
multiple platforms and multiple language bindings.
The *sc2mpd* source comes with a shell script named _ohbuild.sh_ to help
with this. It has several functions:
- Cloning the OpenHome and checking out verified revisions
- Applying a few minor patches to ensure that the build will work in a
simplified environment (e.g. without a c# compiler).
- Creating a tar file of a compact trimmed tree.
- Running the build either from the cloned tree or the tar file.
The tar functions are mostly useful to help with building packages. For a
normal build, the procedure would be as follows:
cd sc2mpd
mkdir /my/place/for/openhome
sh ohbuild.sh -b /my/place/for/openhome
==== Building sc2mpd
*sc2mpd* depends on a number of libraries:
- The link:http://www.gnu.org/software/libmicrohttpd/[microhttpd]
library. Install the development and runtime packages which are currently
named _libmicrohttpd-dev_ and _libmicrohttpd10_ on Debian-derived systems
(use _libmicrohttpd_ and _libmicrohttpd-devel_ for Fedora).
- The link:http://www.mega-nerd.com/SRC/[libsamplerate]
library (_libsamplerate0_ on Debian, _libsamplerate-devel_ for Fedora).
- The *libasound* Alsa interface library (_libasound2-dev_ on Debian,
_alsa-lib-devel_ for Fedora).
Once OpenHome is built and the auxiliary library development packages are
installed, build *sc2mpd*, using the following commands inside the
_sc2mpd_ directory:
sh autogen.sh
./configure --prefix=/usr --with-openhome=/my/place/for/openhome
make
sudo make install
The build uses static Openhome libraries, so you can move the executable to
another machine without needing the Openhome directory (don't forget to
install the _libmicrohttpd_, _libsamplerate_ and _libasound_ runtimes
though).
After restarting *upmpdcli*, it should advertise the _Receiver_ service and
appear in the Songcast Sender menus.
==== Building a Debian package from an sc2mpd tar distribution
Here follows a synopsis of building a debian package for an sc2mpd tar
distribution. You'll need to replace the 1.1.1 and 20151223 versions with
whatever you are building. Note that the 1.1.1 value must match what you
have in the Debian changelog (or update the changelog).
The $distdir and $sc2mpd_src values stand for places where you store the tar
files and the sc2mpd (git) source tree.
mkdir sc2mpd_build
cd sc2mpd_build
cp $distdir/sc2mpd-1.1.1.tar.gz sc2mpd_1.1.1.orig.tar.gz
cp $distdir/openhome-sc2-20151223.tar.gz sc2mpd_1.1.1.orig-openhome.tar.gz
tar xzf sc2mpd_1.1.1.orig.tar.gz
cp -rp $sc2mpd_src/debian sc2mpd-1.1.1/
cd sc2mpd-1.1.1
mkdir openhome
cd openhome
tar xzf ../../sc2mpd_1.1.1.orig-openhome.tar.gz
cd ..
debuild
[[SC2MPD-INSTALL]]
== Annex: Songcast installation walkthrough
If you want to play from a Mac or Windows machine, install the
link:http://www.linn.co.uk/software#songcast[Songcast application]
NOTE: Not all http://oss.linn.co.uk/Releases/Songcast/Davaar/[Songcast
capture application versions] work well with upmpdcli. Lately (03-2017),
the latest version (4.8.535) seems to work fine. In the past, I've had good
luck with 4.4.190 but not with the 4.5 ones (it is possible to get them to
work with *upmpdcli* from the *upplay* control panel, but the Windows app
claims that the *upmpdcli* receiver is unavailable.).
I could not get IP multicast to work with WIFI Receivers (the sound drops
constantly).
There are well-known problems with multicast and WIFI (see for example
http://superuser.com/questions/730288/why-do-some-wifi-routers-block-multicast-packets-going-from-wired-to-wireless[this
superuser.com question]
for detailed explanations). This seems to be dependant on the WIFI hardware
(router/access points) used, so maybe you will have more luck than me.
If some of your Receivers use WIFI, and you experience sound issues, check
that "Unicast" is selected in the Songcast configuration "advanced" panel
on the desktop.
Under most conditions, WIFI data rates should be more than sufficient to
transport Songcast streams (a bit over 1 Mbit/S for 48k/24bits, 700 Kbits/S
for 44.1k/16 bits).
However, Songcast is probably best transported over a wired connection. If
you are doing this over WIFI and experiencing glitches, the wireless is the
first suspect.
If the Sender is a *upmpdcli* host, you should probably also install the
link:http://www.lesbonscomptes.com/upplay/[upplay] Control Point
somewhere. Recent upplay versions include a tool to control Sender and
Receiver instances. This is less necessary if the Sender is on Windows or
Mac, as the Songcast application on these platforms includes a limited
connection tool (no multiroom).
Download and install the *upmpdcli* and *sc2mpd* packages for your Linux
system. See
link:http://www.lesbonscomptes.com/upmpdcli/downloads.html#packages[the
download page here].
When using a single Receiver, things should just work, the _UpMpd_
Receiver should appear in the Songcast app on the host (or in the *upplay*
control panel).
WARNING: There is *no software volume control* for the *upmpdcli* Songcast
Receivers for now: use either a local mixer or the little round things on
the pre-amps. Set the volume low when experimenting !
NOTE: The receiver side does not work too well on Raspberry Pis using an
USB DAC (as far as I could see). The reason may be that the data rate of
the uncompressed stream is just too much for the poor Pi Ethernet/USB
chip. Things work just fine with an I2S DAC (or on HDMI probably). When on
WIFI, the results are sometimes irregular too, depending on the quality of
the connection. If you have no Ethernet cabling, Ethernet over power lines
may work better than WIFI. The best combination of network and DAC link is
definitely Wired and I2S (or HDMI).
When using multiple Receiver instances, you need to at least customize
their names, and you want to take care of synchronization issues. You will
need to take a look at a bit more documentation:
- xref:friendlyname[+friendlyname+]
- xref:UPMPDCLI-MULTIROOM-SYNC[audio synchronization issues and *sc2mpd*
configuration].
[[SENDER-EXTSOURCES]]
== Annex: Setting up external audio sources for the Songcast Sender
The *upmpdcli* Sender modes are controlled by switching OpenHome
Sources. By default, and if the *sc2mpd* package is installed, *upmpdcli*
will create 'PL-to-Songcast' and 'RD-to-Songcast' sources for broadcasting
its playlist or radio streams to Songcast.
As explained in the main body, there is nothing magical with this: *mpd*
just streams to a FIFO which is read by the *mpd2sc* command, which then
broadcasts it. This pipe is set up by a script (_scmakempdsender_).
Under certain conditions, if *upmpdcli* finds other scripts in a designated
directory, it will create more sources, and start them when the
corresponding source is selected (of course, it expects the script to
create a Songcast Sender pipe).
The *upmpdcli* source comes with a sample script which sets things up for
*mpd2sc* to read *arecord* output, allowing multiroom playing of an
external analog source (line-in). The sample script is flexible enough to
manage different inputs without code changes, and there are comments at the
top which give detailed explanations. The parts of more general interest
will be a bit expanded here (see below). If you want to use the script
itself, you need to look at the comments. You will find the script under
'samplescripts/Analog-Input' in the source tree.
Based on the same mechanism (but quite different code inside the script)
there is also a nice
link:https://www.lesbonscomptes.com/upmpdcli/github-issues/upmpdcli-html/issue-71.html[HOWTO]
explaining how to link a Bluetooth device to Songcast.
The general idea is that upmpdcli will create an Openhome Source for each
script it finds inside a designated directory. By default, the directory is
+/usr/share/upmpdcli/src_scripts+, but it can be changed by setting the
+ohsrc_scripts_dir+ configuration variable inside +/etc/upmpdcli.conf+
For managing analog sources, entries inside the directory will typically
be created as symbolic links to the sample script, which is installed as
+/usr/share/upmpdcli/Analog-Input+. For doing other things, the scripts
will not be links, but they must still be named a bit specially.
The scripts (or links) must be named like _SourceType_-_SourceName_, where
_SourceType_ MUST BE one of +Analog+, +Digital+, or +Hdmi+, (which are all
the same, and for display purpose only), and you can choose _SourceName_ as
you wish, but it should contain no space characters.
The Source will appear with type +Analog+, +Digital+ or +Hdmi+ and name
_SourceName_ in an OpenHome Source select dialog (e.g from *upplay*).
The +Analog-Input+ sample script has provisions for reading the device name
and setup/teardown instructions from external files, so that it does not
need to be modified. This is only relevant for the sample, please have a
look at the comments for details.
[[COMMAND-ENVIRON]]
== Annex: command line and environment
In most situations, *upmpdcli* will be run as follows:
upmpdcli -D -c /etc/upmpdcli.conf
The `-D` option tells *upmpdcli* to fork and run in background. The `-c`
option specifies a configuration file.
See the upmpdcli(1) manual page for more information about the command
line.
Some of the essential configuration parameters can be set from the command
line, a configuration file, or the environment in this order of
priority. It would be rather confusing to use a mix of methods, so you
should probably chose one.
All parameters have defaults, and a minimal installation will need no
customisation at all.
|========================
|What|Command line|Environment|Config variable
|Configuration file name|-c config|$UPMPD_CONFIG|
|Host name or IP address where *MPD* runs|-h mpdhost|$UPMPD_HOST|mpdhost
|TCP port for *MPD*|-p mpdport|$UPMPD_PORT|mpdport
|UPnP "friendly name" for the device. This gets displayed in network search
results.|-f friendlyname|$UPMPD_FRIENDLYNAME|friendlyname
|Log file name. Leave empty for stderr|-d logfilename||logfilename
|Verbosity level (0-4)|-l loglevel||loglevel
|UPnP network interface|-i iface|$UPMPD_UPNPIFACE|upnpiface
|UPnP port|-P port|$UPMPD_UPNPPORT|upnpport
|===========================
[[UPMPDCLI-CONFIG-GUI]]
== Annex: the upmpdcli-config GUI configuration editor.
The upmdpcli-config tool presents a graphical interface for creating an
upmpdcli configuration file. It presents different tabs with controls,
directly matching the organisation of the parameters in the documentation.
Both the tool and the manual are generated from data in the reference
configuration distributed with the package (typically
'/usr/share/upmpdcli/upmpdcli.conf-dist').
You can use the tool to create a configuration from scratch (just tweak
what you want, then save the file), or for editing an existing
configuration. The latter can be done either by passing the configuration
file name on the command line, or by using the 'Open' menu entry. If you
use the command line, the parameter automatically becomes the target of a
future 'Save' command (you can change it by using 'Save as'). When using
'Open', you will be asked to choose an output destination when saving.
Each control has a label, and an longer explanation in a tooltip, which you
can see by leaving the cursor on the label.
Once you are satisfied with the changes, you can save the file, and move it
to its normal location if needed (e.g. '/etc/upmpdcli.conf').
Only the parameters which were changed in the configuration you edit (if
not starting from scratched), and those which you change through the
interface, will be saved to the output. Parameters unchanged from the
defaults will not appear at all, allowing for a less cluttered file.
[[SCWEB]]
== Annex: the scweb Songcast control interface.
This is only useful if you have no machine on which to run *upplay*, or
*Bubble DS Next*. Either are easier to use than the web
tool.
To avoid having to access the command line interface to control the
*Songcast* groups, *upmpdcli* comes with a small Web server which uses
*scctl* to actually do the work. This is found inside the `web/`
subdirectory inside the *upmpdcli* source tree.
The server is based on the
link:http://bottlepy.org/docs/dev/index.html[Bottle Python Web Framework]
and it only depends on Python (version 2 and 3 are supported by *Bottle*,
but the current app only works with Python 2).
You can use the `scweb-standalone.py` script to manually start the
interface:
python2 ./scweb-standalone.py
This will start a server on localhost, on port 8680 by default which is
good for testing, but not very useful. Use the -a 0.0.0.0 option to let the
server answer on all local addresses (or specify the address to use a
specific interface):
python2 ./scweb-standalone.py -a 0.0.0.0
-p can be used to specify a port.
Once started, connecting to the server from any browser should hopefully
display a reasonably self-explanatory interface.
Recent *upmpdcli* packages install the web app as a service named
*scweb*. The service is not started by default though, you need to edit
`/etc/default/scweb`.