Selecting the download stream

As described in Starting the download, in options you can set the:

Download bitrate with the AVAssetDownloadTaskMinimumRequiredMediaBitrateKey key.
Download resolution with the AVAssetDownloadTaskMinimumRequiredPresentationSizeKey key. (Only available on iOS 14 and above.)

However, this cannot guarantee the actual download bitrate or resolution will equal the expected value; see the Apple documents AVAssetDownloadTaskMinimumRequiredMediaBitrateKey and AVAssetDownloadTaskMinimumRequiredPresentationSizeKey. To address this issue, the Player SDK provides the prepareDownload API to return a preparing OTVPersistenceAsset instance, from which the available bitrates and resolutions can be retrieved when the state changes to prepared.

You will need to select one bitrate or resolution from the available bitrates array returned from OTVPersistenceAsset.mediaInfo.availableStreamInfo, and set the chosen value back to OTVPersistenceAsset.mediaInfo. selectedStreamInfo.

To set up DRM, an OTVLicenseDelegate licenseDelegate must be set by calling OTVPersistenceAsset.setupFPS(with: licenseDelegate); ignore this for download of clear content.

When the OTVPersistenceAsset instance has bitrate or resolution selected, and its DRM is set up, it can be passed to startDownload to start the downloading.

Preparing for a download

CODE

// Observe the OTVAssetDownloadStateChanged before calling `prepareDownload`
NotificationCenter.default.addObserver(
      self,
      selector: #selector(self.stateChanged),
      name: .OTVAssetDownloadStateChanged,
      object: nil)

let assetURL = "https://d3bqrzf9w11pn3.cloudfront.net/basic_hls_bbb_encrypted/index.m3u8"
let assetName = "Big Buck Bunny"

// prepare for a download
// opyPersistenceAsset must be retained for later downloading
let opyPersistenceAsset = OTVPersistenceManager.shared.prepareDownload(url: assetURL, title: assetName)

// setup DRM for download
let licenseDelegate = OTVSSPLicenseDelegate(certificateURL: certificateURL, licenseURL: licenseURL)
licenseDelegate .setStream(token: token, with: assetURL)
opyPersistenceAsset.setupFPS(with: licenseDelegate )

// Handle state changed event
@objc func stateChanged(notification: NSNotification) {
    let title = notification.userInfo![OTVPersistenceAsset.Keys.name] as! String
    let stateString = notification.userInfo![OTVPersistenceAsset.Keys.downloadState] as! String
	guard let state = OTVDownloadState(rawValue: stateString) else {
		return
	}
	swicth(state) {
	case .prepared:
		handlePreparedDownload()
	...
	}
}

Selecting a stream to download

CODE

func handlePreparedDownload() {
	let allStreamInfo = opyPersistenceAsset?.mediaInfo?.availableStreamInfo
	var selectedStreamInfo: OTVStreamInfo?
	for streamInfo in allStreamInfo  {
		let bitrate = streamInfo.bitrate
		let resolution = streamInfo.resolution
		// find the bitrate or resolution you want to download
		selectedStreamInfo = streamInfo
		break
	}
	opyPersistenceAsset?.mediaInfo?.selectedStreamInfo = selectedStreamInfo
	//Download all available tracks (audio/subtitle) for the asset to be downloaded. Use option .preferred to download only the preferred tracks. 
	opyPersistenceAsset?.mediaSelections = .all
	OTVPersistenceManager.shared.startDownload(asset: persistanceAsset, artwork: nil, options: nil)
}