This section is informative.
SMIL 3.0 Server Playlist Profile is a new profile introduced in SMIL 3.0. It was not part of the SMIL 2.1.
This section is informative.
The SMIL 3.0 Server Playlist Profile is a collection of SMIL 3.0 modules that provide support for the SMIL 3.0 language within the context of the playlist used to manage radio/tv streams in the audio/video servers. Using the playlist specified in SMIL, the server composes a set of audio/video files and/or online input streams to generate an output stream which is transmitted to the final user.
This section is informative.
Server playlists allow companies to generate a live stream from a set of contents. Figure shows the performance schema. Using stored audios and videos and live streams, a computing system can get and combine them in the way specified in a document named playlist.
Nowadays these systems run as follow:
But, if we have SMIL, why do not we use it into these systems?
We could have a standard format to define the playlist. Thus, we can use an editor from one company and a server from another one, the playlist can be reused for different services, even these tasks can be done by different companies (production studio/content provider, TV channel/service provider). In only one word, we could have "interoperability". Moreover, we can introduce new functionality and build more powerful systems.
So the focus here is having a SERVER-ORIENTED SMIL format.
In this section we will try to define how the server playlists can be used, and thus, to clarify what the main purpose of this profile is.
The figure depicts how a live service works. Live audio/video services may use either stored or live contents.
When live contents are used a tool called encoder or producer captures audio and video contents from an external source (e.g., a camera and a microphone), and then generates and sends a continuous stream of data packets to a streaming server. The server delivers then some of these data packets to the users who have requested the information, after applying the necessary changes (by changing sequence numbers, removing or adding specific fields in the header of the data packets, etc.).
On the other hand, when stored contents are used, most software providers have different solutions to generate live streams using a set of previously-encoded files. We may call these solutions "oepostencoders" and the main providers have the solutions which follow.
The live stream is after that, delivered to the final user through the Internet or broadcasted using common radio/TV channel.
RealNetworks is one of the companies which implements this type of systems. To generate its live streams, it mainly uses a program called slta. This program uses a plain-text file where the path and names of the files to be used are provided. When the program starts, it opens the playlist file and starts to deliver data packets to the server by putting the files into a sequence. When the program reaches the end of the playlist or a certain length of this playlist, it may stop or it may read it and start again (the slta can loop the list of pre-recorded files either a specified number of times or indefinitely) Also, it is possible to add meta-data. As far as we know, it is impossible to play with the layout of the files. For instance, if we are a content provider working for several broadcasters we need to generate different versions of the same contents even if small variations are needed (like the insertion of a logo image). Also, timing functionality is very limited and only stored contents can be used. An example of a slta playlist follows:
losberrones_10anos_ladelatele-a.rm?title="La de la
Asturies.Com"&author="Asturies.Com Canal UN"
elpresi_laxatapinta-a.rm?title="La xata pinta"&author="El
In the example, the playlist uses 7 files in rm format and each of the files has two associated meta-data items: a title and the name of the author. The slta will open these files in a sequence or in random order depending on an available input parameter.
Other developers are Microsoft (Windows Media Services) and Apple (Darwin/Quicktime Streaming Server). These companies provide what they call Server playlists. They have included a management tool to create and manage these lists of contents. A module in the server uses these playlists and performs actions similar to those exposed in the case of RealNetworks solutions. A reduced set of SMIL 2.0 is available in Microsoft solutions. As far as we know, it is impossible to play with layout (the elements available in Microsoft Server playlists are those in http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmsrvsdk/htm/playlistelements.asp).
An example of a Microsoft Server Playlist follows:
<media src="c:\wmpub\wmroot\audio1.wma" clipBegin="2:42"
<media src="c:\wmpub\wmroot\audio2.wma" clipBegin="0:00"
<media src="c:\wmpub\wmroot\audio3.wma" clipBegin="2min"
<media src="c:\wmpub\wmroot\audio4.wma" clipBegin="0h"
In the example, the playlist uses 4 files in wma format which will be opened sequentially with different starting points along their internal timeline.
So the basic idea behind the Server Playlist Profile is to:
As mentioned before, the most popular multimedia platforms permit the usage of server playlists in different ways. A good point to start would be to use SMIL in all of these server playlists. The migration to SMIL has three levels of complexity for these platforms:
To allow either audio or video media objects
To allow metadata associated to the SMIL file or to each of the media items in the document
To allow sequences
To avoid the usage of any layout functionality
|All this functionality is currently supported by Microsoft, and RealNetworks only needs to update the parser of the slta.|
|To support clipBegin, clipEnd, dur, begin, end, repeatCount and
To consider excl
To consider switch (to define alternative sources for redundancy purposes)
|Supported by Microsoft, but RealNetworks requires considerable changes in the slta.|
|Changes in layout||Not supported, requires deep changes in all platforms|
Most server playlist technologies (at least RealNetworks) only allow the usage of stored contents. It could be possible to have more complex services where two types of companies are involved: Content providers and Broadcasters.
Content providers may generate the contents and sell these contents to broadcasters. On the other hand, broadcasters may combine the contents of different providers in order to have a continuous stream of contents (24/7)
For example, TVE, BBC and CNN (broadcasters) buy a football match to AudioVisual Sport (Sport Content Provider). This match is transmitted from the AudioVisual Sport server and each of the broadcasters would like to broadcast the match, combined with other contents depending on their scheduled program. One example is showed in the table. In it, the broadcaster combines the contents provided by different content providers with their own contents (either stored or live).
|21:00||12:00||Coronation Avenue||Equirrel Productions||Stored|
|22:00||22:30||Who wants to be poor?||Funny Productions Inc.||Stored|
|22:30||00:30||Football: Barcelona C.F vs Manchester United||AudioVisual Sport||Live|
|01:00||02:15||International Cinema: Xicu'l Toperu||Producciones Esbardu||Stored|
Another example are broadcasters which have a common set of contents and then certain slots where specific contents are broadcasted depending on the region (in local languages, reporting about local news, etc.). Each local transmission may retrieve the general contents as stated on their playlists and combine them with other contents designed for that particular region.
|9:00||14:00||National programs||National TV||Live|
|15:00||16:00||Daily report: The salmon||Own||Stored|
|16:00||00:30||National programs||National TV||Live|
This section is informative.
The SMIL 3.0 Server Playlist Profile is defined as a markup language. The syntax of this language is formally described with a document type definition (DTD) or an XML Schema which is based on the SMIL modules as defined in "The SMIL 3.0 Modules".
In the text in this profile specification, the term Server Playlist Profile will be considered to refer exclusively to the SMIL 3.0 Server Playlist Profile as defined in this document.
The Mobile Profile design requirements are:
This section is normative.
This version of SMIL provides a definition of strictly conforming Server Playlist Profile documents, which are restricted to tags and attributes from the SMIL 3.0 namespace. In the future, the language described in this profile may be extended by other W3C Recommendations, or by private extensions. For these extensions, the following rules must be obeyed:
Conformant Server Playlist Profile user agents are expected to handle documents containing extensions that obey these two rules.
The Server Playlist Profile is a conforming SMIL 3.0 specification. The rules for defining conformant documents are provided in the SMIL in the SMIL document. Note that while the section is written for the SMIL 3.0 Language profile, all of the rules apply to the Server Playlist Profile as well, with the exception that the Server Playlist Profile's namespace should be used instead of the SMIL 3.0 Language Profile's namespace and the Server Playlist Profile's DOCTYPE declaration should be used instead of the SMIL 3.0 Language Profile DOCTYPE declaration.
<smil xmlns="http://www.w3.org/2006/SMIL30/WD/ServerPlaylist"> ... </smil>
The default namespace declaration must be
Language designers and implementors wishing to extend the Server Playlist Profile must consider the implications of the use of namespace extension syntax. Please consult the section on Scalable Profiles for restrictions and recommendations for best practice when extending SMIL.
Server Playlist Profile DOCTYPE declaration
A SMIL 3.0 document can contain the following DOCTYPE declaration:
The SMIL 3.0 Mobile Profile DOCTYPE is:
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 3.0 Mobile//EN" "http://www.w3.org/2006/SMIL30/WD/SMIL30Mobile.dtd">
If a document contains this declaration, it must be a valid XML
Note that this implies that extensions to the syntax defined in the DTD are not allowed. If the document is invalid, the user agent should issue an error.
Since the Server Playlist Profile defines a conforming SMIL document, the rules for defining conformant user agents are the same as provided in the Conforming SMIL 3.0 Language User Agents in the SMIL 3.0 Language Profile document, with the exception that the conforming user agent must support the Server Playlist Profile's namespace instead of the SMIL Language Profile's namespace.
The Server Playlist Profile supports the SMIL features for basic multimedia presentations. It uses only modules from the SMIL 3.0 Recommendation. As the language profile includes the mandatory modules, it is a SMIL Host Language conforming language profile. This language profile includes the following SMIL 3.0 modules:
The collection names contained in the following table define the Server Playlist Profile vocabulary.
|SMIL 3.0 Server Playlist Profile|
|Collection Name||Elements in Collection|
|Layout||region, root-layout, layout, regPoint|
|MediaContent||text, img, audio, video, ref, textstream|
|Structure||smil, head, body|
In the following sections, we define the set of elements and attributes used in each of the modules included in the Server Playlist Profile. The content model for each element is described. The content model of an element is a description of elements which can appear as its direct children. The special content model "EMPTY" means that a given element may not have children.
|Collection Name||Attributes in Collection|
|Core||id (ID), class (NMTOKEN), title (CDATA), alt (CDATA), longdesc (CDATA), xml:base (CDATA)|
The id, class and title attributes in the collection Core are defined for all the elements of the Server Playlist Profile. The id attribute is used in the Server Playlist Profile to assign a unique XML identifier to every element in a SMIL document.
A conforming Server Playlist Profile document should not use the SMIL 1.0 attributes that have been depreciated in SMIL 2.0. Server Playlist Profile implementations are not required to support these attributes. This would be considered an unjustified burden for the targeted constraint devices. The unsupported depreciated SMIL 1.0 attributes are the following: anchor, background-color, clip-begin, clip-end, repeat; and the additional depreciated test attributes of Content Control: system-bitrate, system-captions, system-language, system-required, system-screen-size, and, system-screen-depth.
The Layout Modules provide a framework for spatial layout of visual components. The Layout Modules define semantics for the region, root-layout, layout and the regPoint elements. The Server Playlist Profile includes the Layout functionality of the BasicLayout, AudioLayout, BackgroundTilingLayout, and AlignmentLayout modules.
In the Server Playlist Profile, Layout elements can have the following
attributes and content model :
|region||Core, I18n, Test, backgroundColor, showBackground (always | whenActive), , fit (fill | hidden | meet | scroll | slice), width, height, left, right, top, soundLevel, z-index, skip-content, regionName||EMPTY|
|root-layout||Core, I18n, Test, backgroundColor , width, height, skip-content||EMPTY|
|layout||Core, I18n, Test, type||(root-layout | region | regPoint)*|
|regPoint||Core, I18n, Test, top, , left, right, regAlign ( topLeft|topMid | topRight | midLeft | center | midRight | bottomLeft | bottomMid | bottomRight ), skip-content||EMPTY|
The Media Object Modules provide a framework for declaring media. The Media Object Modules define semantics for the ref, audio, img, video, text, and textstream elements. The Server Playlist Profile includes the Media Object functionality of the BasicMedia and MediaClipping modules.
In the Mobile Profile, media elements can have the following attributes and content model:
|Media Object Module|
|text, img, audio, video, ref, textstream||Core, I18n, Timing, Test, region, fill (freeze | remove | hold | transition | auto | default), , copyright, abstract, src, type, erase, mediaRepeat, paramGroup, sensitivity, transIn, transOut, clipBegin, clipEnd, endsync, mediaAlign, regPoint, regAlign, soundAlign, soundLevel.||(param | area | switch)*|
The Metainformation Module provides a framework for describing a document, either to inform the human user or to assist in automation. The Metainformation Module defines semantics for the and elements. The Server Playlist Profile includes the Metainformation functionality of the Metainformation module.
In the Server Playlist Profile, Metainformation elements can have the following attributes and content model :
|Core, I18n, skip-content, content (CDATA), name (CDATA)||EMPTY|
|Core, I18n, skip-content||EMPTY|
The content model of metadata is empty. Profiles that extend the Server Playlist Profile may define their own content model of the metadata element.
The Structure Module provides a framework for structuring a SMIL document. The Structure Module defines semantics for the smil, head, and body elements. The Server Playlist Profile includes the Structure functionality of the Structure module.
In the Server Playlist Profile, the Structure elements can have the following attributes and content model :
|smil||Core, I18n, Test, xmlns||(head?,body?)|
|head||Core, I18n||(*,(,*)?,((layout|switch),*)?, (transition+,*)?, (paramGroup+,*)?)|
|body||Core, I18n, Timing, fill, abstract, , copyright||(Schedule | MediaContent | ContentControl | a )*|
The body element acts as the root element to span the timing tree. The body element has the behavior of a seq element. Timing on the body element is supported. The syncbase of the body element is the application begin time, which is implementation dependent, as is the application end time. Note that the effect of fill on the body element is between the end of the presentation and the application end time, and therefore the effect of fill is implementation dependent.
The Timing and Synchronization Modules provide a framework for describing timing structure, timing control properties and temporal relationships between elements. The Timing and Synchronization Modules define semantics for par and seq elements. In addition, these modules define semantics for attributes including begin, dur, end, repeatCount, repeatDur, min, max. The Server Playlist Profile includes the Timing and Synchronization functionality of the BasicInlineTiming, EventTiming, MinMaxTiming, RepeatTiming, BasicTimeContainers modules.
In the Server Playlist Profile, Timing and Synchronization elements can have the following attributes and content model :
|Timing and Synchronization Module|
|par||Core, I18n, Timing, Test, endsync, fill (freeze | remove | hold | auto | default), abstract, , copyright, region||(Schedule | MediaContent | ContentControl | a)*|
|seq||Core, I18n, Timing, Test, fill (freeze | remove | hold | auto | default), abstract, , copyright, region||(Schedule | MediaContent | ContentControl | a) *|
The Attribute collection Timing is defined as follows:
|Collection Name||Attributes in Collection|
|Timing||begin, dur, end, repeatCount, repeatDur, min, max|
Elements of the Media Object Modules have the attributes describing timing and properties of contents.
The Mobile Profile specifies which types of events can be used as part of the begin and end attribute values. The supported events are described as Event-symbols according to the syntax introduced in the SMIL Timing and Synchronization module.
The supported event symbols in the Mobile Profile are:
|focusInEvent (In DOM Level 2: "DOMFocusIn")||end="foo.focusInEvent"|
|focusOutEvent (In DOM Level 2: "DOMFocusOut")||begin="foo.focusOutEvent"|
|activateEvent (In DOM Level 2: "DOMActivate")||begin="foo.activateEvent"|
As defined by the SMIL syncbase timing semantics, any event timing attributes that reference an invalid time-value description will be treated as if "indefinite" were specified.
<ref id="x" end="30s" src="15s.mpg" /> <ref id="y" end="10s" src="20s.mpg" /> <ref id="z" repeatCount="4" src="5s.mpg" />
x.endEvent occurs at roughly 30s when the active duration is reached, y.endEvent occurs at roughly 10s when the playback of the continuous media is ended early by the active duration being reached, and z.endEvent occurs at roughly 20s when the fourth and final repeat has completed, thus reaching the end of its active duration. The endEvent is delivered to elements which support timing, such as media elements and time containers, and does not bubble.
A media element's bounds are restrained by the bounds of the region in which it is contained., i.e., a media element's bounds do not extend beyond its region's bounds. The inBoundsEvent is delivered to media elements only, and does not bubble.
Note that, unlike with keyboard focus which can only be active on one object at a time, the state of being within an object's bounds can be true for multiple objects simultaneously. For instance, if one object is on top of another and the cursor is placed on top of both objects, both would have raised an inBoundsEvent more recently than the raising of any respective outOfBoundsEvent. If a player does not support a pointer cursor, then these players will typically not generate the inBoundsEvent and outOfBoundEvent events.
A media element's bounds are restrained by its region's bounds, i.e., a media element's bounds do not extend beyond its region's bounds. The outOfBoundsEvent is delivered to media elements only, and does not bubble.
There will be cases where events occur simultaneously. To ensure that each Mobile implementation handles them in the same order, the following order must be used to resolve ties:
Events are listed in order of precedence, e.g., if event #6 in this list occurs at the same time as event #7, then #6 must be raised prior to #7.
The InBoundsEvent, focusInEvent, OutOfBoundsEvent, activateEvent, and focusOutEvent events do not bubble and are delivered to the target media element.
The beginEvent, endEvent and repeatEvent events do not bubble and are delivered to the timed element on which the event occurs.
The Mobile Profile supports an extensible set of events. In order to resolve possible name conflicts with the events that are supported in this profile qualified event names are supported. Namespace prefixes are used to qualify the event names. As a result, the colon is reserved in begin and end attributes for qualifying event names.
<smil ... xmlns:example="http://www.example.com"> <img id="foo" .../> <audio begin="foo.example:focusInEvent".../> ... </smil>
A SMIL document's begin time is defined as the moment a user agent begins the timeline for the overall document. A SMIL document's end time is defined as equal to the end time of the body element.
The Transition Effects Modules provide a framework for describing transitions such as fades and wipes. The Transition Modules define semantics for the transition element. The Server Playlist Profile includes the functionality of the BasicTransitions and FullScreenTransitions modules.
In the Server Playlist Profile, Transition Effects elements have the following attributes and content model :
|Transition Effects Module|
|transition||Core, I18n, Test, dur, type, subtype, startProgress, endProgress, direction, fadeColor, scope, skip-content||EMPTY|
This section is normative.
The Server Playlist Profile Document Type Definition is defined as a set of SMIL