Wowza Streaming Engine™ (WSE) supports XML-based SMIL files, which describe a set of media entries that can be delivered together as a single adaptive bitrate stream. A SMIL file lists each rendition, along with the audio and video characteristics WSE uses to build the manifest delivered to players.
WSE supports the SMIL standard with additional custom elements, attributes, and parameters not specified by the standard. Renditions appear in the manifest in the same order they're listed in the <switch> container element, and players select the first stream in the manifest first. Arrange streams from highest to lowest bitrate so the player selects the highest bitrate stream that current network conditions and available CPU resources allow.
Note: Not all attributes and parameters described below are supported by every streaming protocol. For example, roles apply only to MPEG-DASH streams.
Contents
Example SMIL file
The following example shows the WSE SMIL file format.
<smil> <head></head> <body> <switch> <video src="[source-name]" [attribute-name]="[value]" [attribute-name]="[value]"> <param name="[param-name]" value="[value]" valuetype="data"/> <param name="[param-name]" value="[value]" valuetype="data"/> </video> <video src="[source-name]" [attribute-name]="[value]" [attribute-name]="[value]"> <param name="[param-name]" value="[value]" valuetype="data"/> <param name="[param-name]" value="[value]" valuetype="data"/> </video> <video src="[source-name]" [attribute-name]="[value]" [attribute-name]="[value]"> <param name="[param-name]" value="[value]" valuetype="data"/> <param name="[param-name]" value="[value]" valuetype="data"/> </video><!-- Use to add caption data --><textstream src="[source-name]" system-language="[value1, value2]"> <param name="[param-name]" value="[value]" valuetype="data"></param> </textstream> </switch> </body> </smil>
Switch element
The <switch> element contains the children listed in the table below. Every <video> element must contain at least one bitrate attribute or parameter in order to make the SMIL file compatible with all HTTP streaming protocols.
| Element | Type | Description |
|---|---|---|
<video> |
Container | Attributes that customize the audio and video characteristics of a media entry. Each rendition in the adaptive bitrate stream is defined in its own <video> element. See the Video attributes table for available attributes. Required. |
<param><param> |
Container | A name and value pair that customizes the audio and video characteristics of a media entry. See the Video parameters table for available parameters. Optional. |
<textstream> |
Container | Caption data for the streams in the <switch> element. A SMIL file supports a single <textstream> element. See TextStream element. Optional. |
Video attributes
The <video> element accepts the attributes listed in the table below.
| Attribute | Type | Description |
|---|---|---|
src |
String | The name of the media file or live source stream, such as sample.mp4. Required.
|
systemLanguage |
String | Three-letter code for the language of the audio or video track in the media. |
system-bitrate |
Integer | Combined bitrate of the audio and video tracks in the media. Also available as the systemBitrate parameter. Ignored for MPEG-DASH streams. |
audio-bitrate |
Integer | Bitrate of the audio tracks in the media entry. Also available as the audioBitrate parameter. |
video-bitrate |
Integer | Bitrate of the video tracks in the media entry. Also available as the videoBitrate parameter. |
width |
Integer | Display width of the video track in the media. |
height |
Integer | Display height of the video track in the media. |
title |
String | Title of the media entry. |
begin |
Integer | Position in the stream, in milliseconds, at which playback begins. Use with dur to play a specific section of the source media. |
dur |
Integer | Duration, in seconds, of the stream interval to play. Use with begin to play a specific section of the source media. |
Param attributes
The <param> element within the <video> container may contain the named attributes listed in the table below.
| Attribute | Type | Description |
|---|---|---|
audioOnly |
Boolean | If true, WSE uses the default audio track and ignores all video tracks in the media. |
videoOnly |
Boolean | If true, WSE uses the default video track and ignores all audio tracks in the media. |
audioCodecId |
String | The codec ID of the default audio track in the media entry. If you're unsure of the correct codec string, leave this unset and WSE determines the ID. |
videoCodecId |
String | The codec ID of the default video track in the media entry. If you're unsure of the correct codec string, leave this unset and WSE determines the ID. |
role |
String | Intended role of all audio and video tracks in the media file. Accepts one of the following values:
|
audioRole |
String | Intended role of the default audio track in the media entry. Accepts one of the following values:
|
videoRole |
String | Intended role of the default video track in the media entry. Accepts one of the following values:
|
keyFrameOnly |
Boolean | If true, WSE delivers only the keyframes in the stream's source media, which reduces CPU load. |
mpegdashTag.adaptationSet |
Data | Adaptation set for MPEG-DASH streams. Each unique value creates a separate adaptation set, and all renditions sharing a value are included in the same adaptation set. |
TextStream element
Add caption data to a SMIL file with a single <textstream> container element. For attribute definitions, parameter descriptions, and example usage, see:
- Play VOD streams with WebVTT subtitles using a SMIL file
- Override live caption ingest behavior using a SMIL file
- Play live streams with WebVTT subtitles using a SMIL file
