Created by Bill Reid, last modified by Aanchal Gupta on Feb 01, 2018
Table of Contents
Extends: Node
Description
The Audio node class plays streaming audio.
The Audio node class has no built-in visual UI, but you can build your own UI for the node, including trick play, or showing an album cover or similar graphical image for each song selected by a user.
Fields
| Field | Type | Default | Use |
|---|
| content | ContentNode | NULL | The ContentNode node with the Content Meta-Data for the audio or audio playlist (a sequence of audios) to be played. If a audio playlist is to be played, the ContentNode node must include complete child ContentNode nodes for each audio in the playlist, with all attributes required to play that audio. |
| contentIsPlaylist | Boolean | false | If set to true, enables audio playlists (a sequence of audios to be played). To enable audio playlists, the ContentNode node set in the content field must have children ContentNode nodes for each audio in the playlist. When audio playback is started, all of the audios in the playlist will be played in sequence.
Available since firmware version 7.2 |
| nextContentIndex | integer | -1 | If the contentIsPlaylist field is set to true to enable audio playlists, sets the index of the next audio in the playlist to be played. Setting this field does not immediately change the audio being played, but takes effect when the current audio is completed or skipped. By default, this value is -1, which performs the default index increment operation. After the audio specified by the index in this field begins playing, the field is set to the default -1 again, so the next audio played will be set by the default index increment operation, unless the field is set again to a different index.
Available since firmware version 7.2 |
| loop | Boolean | false | If set to true, the audio or audio playlist (if the contentIsPlaylist field is set to true to enable audio playlists) will be restarted from the beginning after the end is reached.
Available since firmware version 7.2 |
| bufferingStatus | associative array | invalid | Read-Only
Contains information about stream buffering progress and status. This field is valid only while buffering is in progress, both at stream startup or when re-buffering is required. Observers will be notified when any element of the array changes, and also when buffering is complete and the field itself becomes invalid. The array contains the following name - value pairs. | Value | Meaning |
|---|
| percentage | Percent buffering complete as an integer. | | isUnderrun | Boolean value indicating if a stream underrun occurred. |
Available since firmware version 7.2 |
| control | option string | "none" | Sets the desired play state for the audio, such as starting or stopping the audio play. Getting the value of this field returns the most recent value set, or none if no value has been set. In order to dynamically monitor the actual state of the audio, see the state field. | Option | Effect |
|---|
| none | No play state set | | play | Start audio play | | start | Start audio play | | stop | Stop audio play | | pause | Pause audio play | | resume | Resume audio play after a pause | | replay | Replay audio | | prebuffer | Starts buffering the audio stream before the Audio node actually begins playback. Only one audio stream can be buffering in the application at any time. Setting the control field to prebuffer for another audio stream after setting prebuffer for a previous audio stream stops the buffering of the previous audio stream.
Available since firmware version 7.2 | skipcontent | Skip the currently-playing content, and begin playing the next content in the playlist. If the content is not a playlist, or if the current content is the end of the playlist, this will end playback.
Available since firmware version 7.2 |
|
| notificationInterval | time | 0.5 | The interval between notifications to observers of the position field, specified as the number of seconds. If the value is 0, no notifications are delivered. This value may be read or modified at any time. |
| timedMetaDataSelectionKeys | array of strings | [ ] | If the audio stream contains timed meta data such as ID3 tags, any meta data with a key matching an entry in this array will be set into the timedMetaData field. If any entry in this array is "*", then all timed meta data will be selected.
Available since firmware version 7.2 |
| seek | time | invalid | Write-Only
Sets the current position in the audio. The value is the number seconds from the beginning of the stream, specified as a double. |
| contentIndex | integer | -1 | Read-Only
The index of the audio in the audio playlist that is currently playing. Generally, you would only want to check this field if audio playlists are enabled (by setting the contentIsPlaylist field to true), but it is set to 0 when a single audio is playing and audio playlists are not enabled.
Available since firmware version 7.2 |
| timedMetaData | associative array | { } | Read-Only
The most recent timed meta data that has been decoded from the audio stream. Only meta data with a key that matches an entry in timedMetaDataSelectionKeys will be set into this field. The value of this field is an associative array which contains arbitrary keys and values, as found in the audio stream.
Available since firmware version 7.2 |
| state | value string | "none" | Read-Only
Describes the current audio play state, such as if the audio play has been paused. | Value | Meaning |
|---|
| none | No current play state | | buffering | Audio stream is currently buffering | | playing | Audio is currently playing | | paused | Audio is currently paused | | stopped | Audio is currently stopped | | finished | Audio has completed play | | error | An error has occurred in the audio play. The error code and error message can be found in the errorCode and errorMsg fields respectively. |
|
| position | time | invalid | Read-Only
The current position in the audio play, as the number of seconds. |
| duration | time | 0 | Read-Only
The duration of the audio being played, specified in seconds. This becomes valid when playback begins and may change if the audio is dynamic content, such as a live event. |
| errorCode | integer | 0 | Read-Only
The error code associated with the audio play error set in the state field. |
errorMsg | string | "" | Read-Only
An error message describing the audio play error set in the state field. |
| audioFormat | string | "" | Read-Only
Contains the format of the currently playing audio. | Value | Meaning |
|---|
"" | No stream playing | aac | ISO/IEC 14496-3, Advanced Audio Coding | aac_adif | ISO/IEC 14496-3, Advanced Audio Coding, ADIF container | aac_adts | ISO/IEC 14496-3, Advanced Audio Coding, ADTS container | aac_latm | ISO/IEC 14496-3, Advanced Audio Coding, LATM container | ac3 | Dolby Digital | alac | Apple Lossless | dts | DTS Coherent Acoustics | eac3 | Dolby Digital Plus | flac | Free Lossless Audio Codec | mp2 | ISO/IEC 11172-3, MPEG Audio Layer II | mp3 | ISO/IEC 11172-3, MPEG Audio Layer III | none | Stream contains no playable audio | pcm | linear PCM | unknown | Stream contains unknown audio | vorbis | Ogg Vorbis | wma | Microsoft Windows Media Audio | wmapro | Microsoft Windows Media Pro Audio |
|
| streamingSegment | associative array | { } | Read-Only
Information about the audio segment that is currently streaming. This is only meaningful for segmented audio transports, such as DASH and HLS. The associative array has the following entries: | Key | Type | Value |
|---|
| segBitrateBps | integer | Bitrate of the segment in bits per second | | segSequence | integer | The sequence number of the segment in the audio | | segStartTime | time | The start time of the segment from the start of the audio, specified in seconds | | segUrl | string | URL of the segment |
|
Data Bindings
See Content Meta-Data for the required and optional play parameters, and descriptive information for audio playback. Set these parameters in a ContentNode node, and assign the ContentNode node to the content field of the Audio node to apply the parameters to a particular audio content item.
For HTTPS access, note the following Content Meta-Data attributes:
HttpCertificatesFileHttpCookies HttpHeaders HttpSendClientCertificates
These attributes must be set to handle secure HTTP transfers of audio files. Note that this is a different HTTPS mechanism than used for other SceneGraph nodes as described in roHttpAgent.
Example
Example application: AudioExample.zip
AudioExample.zip uses a LabelList node to select from several spoken audio examples. The Content Meta-Data for the example is found in the pkg:/server/audiocontent.xml file, read into a ContentNode node by the Task node audiocontentreader.xml component file.
