isSpatialAudio_(tag) {
    const channels = tag.getAttributeValue('CHANNELS');
    if (!channels) {
      return false;
    }
    const channelsParts = channels.split('/');
    if (channelsParts.length != 2) {
      return false;
    }
    return channelsParts[1] === 'JOC' || channelsParts[1].includes('ATMOS');
  }
Get the spatial audio information for an HLS audio track.
In HLS the channels field indicates the number of audio channels that the
stream has (eg: 2). In the case of Dolby Atmos (EAC-3), the complexity is
expressed with the number of channels followed by the word JOC
(eg: 16/JOC), so 16 would be the number of channels (eg: 7.3.6 layout),
and JOC indicates that the stream has spatial audio. For Dolby AC-4 ATMOS,
it's necessary search ATMOS word.
@see https://developer.apple.com/documentation/http-live-streaming/hls-authoring-specification-for-apple-devices-appendixes
@see https://ott.dolby.com/OnDelKits/AC-4/Dolby_AC-4_Online_Delivery_Kit_1.5/Documentation/Specs/AC4_HLS/help_files/topics/hls_playlist_c_codec_indication_ims.html

@param {!shaka.hls.Tag} tag
@return {boolean}
@private