roAudioPlayer

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Last updated: Aug 07, 2024
4 min read

 

An audio player is used to play back audio files using the generic ifMediaTransport interface. If the message port is set, the object will send events of the type roAudioEvent. All object calls are asynchronous. In other words, audio playback is handled in a different thread from the script. The script may continue to run while audio is playing. The JavaScript equivalent is to use the HTML audio tag.

ifMessagePort

SetPort(port As roMessagePort) As Void

Posts messages of type roAudioEvent to the attached message port.

ifUserData

SetUserData(user_data As Object)

Sets the user data that will be returned when events are raised.

GetUserData() As Object

Returns the user data that has previously been set via SetUserData(). It will return Invalid if no data has been set.

IfIdentity

GetIdentity() As Integer

The ifIdentity interface has been deprecated. We recommend using the ifUserData interface instead.

ifMediaTransport 

See roVideoPlayer for a description of ifMediaTransport methods.

ifAudioControl

SetPcmAudioOutputs(outputs As Dynamic) As Boolean

Specifies which audio connectors should output PCM audio. This method accepts an roAudioOutput instance or an array of roAudioOutput instances.

SetCompressedAudioOutputs(outputs As Dynamic) As Boolean

Specifies which audio connectors should output compressed audio (e.g. Dolby AC3 encoded audio). This method accepts an roAudioOutput instance or an array of roAudioOutput instances. 

When the SetPcmAudioOutputs() or SetCompressedAudioOutputs() method is  called, it will override the settings of the following ifAudioControl methods: SetAudioOutput(), MapStereoOutput(), SetUsbAudioPort(), MapDigitalOutput().

SetMultichannelAudioOutputs(array As Object) As Boolean
SetAudioMode(audio_mode As Integer) As Boolean

Sets the audio mode of the roAudioPlayer object. This method accepts the following values:

  • 0: AC3 Surround 

  • 1: AC3 mixed down to stereo 

  • 2: No audio

  • 3: Left

  • 4: Right 

Options 0 and 1 only apply to video files, while options 2, 3, and 4 apply to all audio sources.

SetVolume(volume As Dynamic) As Boolean

Specifies the volume of the audio output as either a percentage or decibel amount. To use a percentage measurement, pass an integer value between 0 and 100. To use a decibel measurement, pass an roAssociativeArray containing a single {db:<value As Float>} parameter. The decibel measurement is an absolute value: passing 0 specifies no change to the audio output, and the effective range of measurements is from approximately -80 to 20 decibels.

The volume value is clipped prior to use (i.e. SetVoume(101) will set the volume to 100 and return True). The volume is the same for all mapped outputs and USB/SPDIF/analog.

Separate volume levels are stored for roAudioPlayer and roVideoPlayer.

SetChannelVolumes(channel_mask As Integer, volume As Integer) As Boolean

You can control the volume of individual audio channels. This volume command takes a hex channel mask, which determines the channels to apply the volume to, and a level, which is a percentage of the full scale. The volume control works according to audio channel rather than the output. The channel mask is a bit mask with the following bits for MP3 output:

  • &H01: Left

  • &H02: Right

  • &H03: Both left and right

SetPreferredAudio(description As String) As Boolean

Selects which audio track to use if there are multiple audio tracks in the stream. See the Preferred Streams section on the roVideoPlayer page for more details.

ConfigureAudioResources() As Boolean

SetAudioDelay(delay_in_milliseconds As Integer) As Boolean

Adds a presentation time stamp (PTS) offset to the audio. This makes it possible to adjust for file multiplexing differences. Delays are limited to 150ms or less. Currently, the system software only supports positive delays; therefore, if you need to set the audio ahead of the video, you will need to use SetVideoDelay() instead.

SetVideoDelay(delay_in_milliseconds As Integer) As Boolean

Adds a presentation time stamp (PTS) offset to the video. This makes it possible to adjust for file multiplexing differences. Delays are limited to 150ms or less.

StoreEncryptionKey(a As String, b As String) As Boolean
 
StoreObfuscatedEncryptionKey(a As String, b As String) As Boolean

 

Deprecated Methods

SetAudioOutput(audio_output As Integer) As Boolean
MapStereoOutput(mapping As Integer) As Boolean
MapDigitalOutput(mapping As Integer) As Boolean
SetStereoMappingSpan(a As Integer) As Boolean
SetAudioStream(stream_index As Integer) As Boolean
SetSpdifMute(a As Boolean) As Boolean
SetUsbAudioPort(a As Integer) As Boolean
SetAudioOutputAux(audio_output As Integer) As Boolean
SetAudioModeAux(audio_mode As Integer) As Boolean
MapStereoOutputAux(mapping As Integer) As Boolean

SetVolumeAux(volume As Integer) As Boolean
SetChannelVolumesAux(channel_mask As Integer, volume As Integer) As Boolean
SetAudioStreamAux(stream_index As Integer) As Boolean

Configuring Audio Outputs

If a audio/video file is playing or has played, you need to call Stop() before changing the audio output.

The following script shows how to use the SetPcmAudioOutputs() and SetCompressedAudioOutputs() methods in conjunction with roAudioOutput. The audio/video player is configured to output decoded audio to the analog output or compressed audio to the HDMI® and SPDIF outputs.

ao1=CreateObject("roAudioOutput", "Analog") ao2=CreateObject("roAudioOutput", "HDMI") ao3=CreateObject("roAudioOutput", "SPDIF") a1=CreateObject("roAudioPlayer") a1.SetPcmAudioOutputs(ao1)   ar = CreateObject("roArray", 2, true) ar[0] = ao2 ar[1] = ao3 a1.SetCompressedAudioOutputs(ar)

This script sets audio output to the third analog audio port:

analog3 = CreateObject("roAudioOutput", "analog:3") video = CreateObject("roVideoPlayer") video.SetPcmAudioOutputs(analog3)

This script configures multiple outputs for an audio player:

analogOut = CreateObject("roAudioOutput", "analog") hdmiOut = CreateObject("roAudioOutput", "hdmi") audio = CreateObject("roAudioPlayer") audio.SetPcmAudioOutputs([analogOut, hdmiOut])

This script sets the volume level for individual channels:

Playing Multiple Audio Files Simultaneously

Multiple MP3 files, as well as the audio track of a video file, can be played to any combination of the following:

  • Analog outputs

  • SPDIF / HDMI

  • USB

Only a single file can be sent to an output at any given time. For example, two roAudioPlayers cannot simultaneously play to the SPDIF output. The second one to attempt a PlayFile will get an error. To free an output, the audio or video stream must be stopped (using the ifMediaTransport Stop or StopClear calls).

Note the following about multiple audio-file functionality:

  • The onboard analog audio output and HDMI output are clocked by the same sample-rate clock. Therefore, if different content is being played out of each, the content must have the same sample rate.

  • Currently, only a single set of USB speakers is supported.

  • Each audio and video stream played consumes some of the finite CPU resources. The amount consumed depends on the bitrates of the streams. Testing is the only way to determine whether a given set of audio files can be played at the same time as a video. The maximum recommended usage is a 16Mbps video file with three simultaneous MP3 160kbps streams.

This script plays a video with audio over HDMI and an MP3 file to the onboard analog port:

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