Alternate audio

Alternate, or late-binding, audio allows you to switch among available audio tracks for a video track. This way, users can select a language track when the video is played.

When TVSDK creates the MediaPlayerItem instance for the current video, it creates an AudioTrack item for each available audio track. The item contains a name property, a string that typically contains a user-recognizable description of the language of that track. The item also contains information about whether to use that track by default.

When it is time to play the video, you can ask for a list of available audio tracks, optionally let the user choose one, and set the video to play with the selected track.

Although rare, if an additional audio track becomes available after it creates the MediaPlayerItem, TVSDK fires a MediaPlayerItem.AUDIO_UPDATED event.

Added APIs

The following APIs have been added to support alternate audio:

hasAlternateAudio

If the specified media has an alternate audio track, other than default track, this boolean function returns true. If there is no alternate audio track, the function returns false.

bool MediaPlayerItemImpl::hasAlternateAudio() const {
    return _hasAlternateAudio;
}

** getAudioTracks**

This function returns list of all the current available audio tracks in a specified media.

virtual PSDKErrorCode getAudioTracks(PSDKImmutableArray<AudioTrack>*& out) const {
if (_audioTracks) {
    out = _audioTracks;
    out->addRef();
    return kECSuccess;
    }
    return kECDataNotAvailable;
}

getSelectedAudioTrack

This function that returns the currently selected alternate audio track and properties such as language. The auto-selection of track can also be extracted.

PSDKErrorCode MediaPlayerItemImpl::getSelectedAudioTrack(AudioTrack &out) const {
    out = _currentAudioTrack;
    return kECSuccess;
}

selectAudioTrack

This function selects an alternate audio track to play.

PSDKErrorCode MediaPlayerItemImpl::selectAudioTrack(const AudioTrack &audioTrack) {
    _lastPlayedAudioTrack = _currentAudioTrack;
    if(_mediaPlayer && _mediaPlayer->_trickPlay)
        return kECUnsupportedOperation;
    _currentAudioTrack = audioTrack;
    PSDKErrorCode result = kECSuccess;
    if (_currentAudioTrack) {
        media::TimeLine* timeline = NULL;
        if (_mediaPlayer->_fragHttpStreamer)
            _mediaPlayer->_fragHttpStreamer->GetTimeLine(&timeline);
        if (timeline) {
            for (int32_t i = timeline->GetFirstPeriodIndex(); i <= timeline->GetLastPeriodIndex(); i++){
                media::ErrorCode error = selectTrack(timeline,_mediaPlayer->_fragHttpStreamer, i, audioTrack.getName(), media::kSTTAudioIndex);
                return _mediaPlayer->convertToPSDKError(error);
            }
        }
    }
    return result;
}

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