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theodab
73 lines
2.9 KiB
Markdown
73 lines
2.9 KiB
Markdown
# Preload API
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In some situations, you may wish to begin loading an asset before Shaka Player
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has been attached to a video, or before you have fully committed to playing it.
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Perhaps you have a menu in which users select multiple assets, and you want to
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preload the assets they mouse over to reduce load latency when those assets are
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selected.
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In situations like that, the Shaka Player preload API can be useful.
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#### Basic Usage
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To preload an asset, call the preload method on a player instance.
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```js
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async function initPlayer() {
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const player = new shaka.Player();
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const preloadManager = await player.preload(
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'https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd');
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if (preloadManager) {
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// The asset is something that can be preloaded. Once you have this manager,
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// you can load it later by passing it to the load method:
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await player.load(preloadManager);
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// If you decide to not play the preloaded asset, you can instead destroy
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// the preload manager:
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await preloadManager.destroy();
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} else {
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// This asset is something that cannot be preloaded (for instance, a raw
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// media file, or browser-based HLS on Safari), so the promise of the
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// preload method yielded null.
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}
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}
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```
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You need a player instance to preload an asset, and you must use the returned
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preloadManager on the same player instance.
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The preloading process loads the manifest and first segments of the asset. It
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will not load the whole asset ahead of time.
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If you need to define any response or request filters for your assets to be
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downloaded, remember to do it before calling `player.preload`.
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The preload method can be provided an optional startTime and mimeType parameter,
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much the same as the load method.
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```js
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const preloadManager = await player.preload(
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'https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd',
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15, 'application/dash+xml');
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```
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In order to cancel a preload in process, you can call the `destroy` method on
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the preloadManager.
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If you want to configure how many segments are preloaded by the preloadManager,
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set the `streaming.segmentPrefetchLimit` configuration value before calling
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`player.preload`.
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#### Saving Preloaders
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The preload API can also be used to unload the player while saving some data
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from the playback session, to allow for playback to resume in the future
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without having to download as much.
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To do this, instead of calling unload on the player, call the
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unloadAndSavePreload method:
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```js
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// This both unloads the player, and creates a preload manager for the currently
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// playing asset.
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const preloadManager = await player.unloadAndSavePreload();
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```
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The resulting preload manager can be used just like one created via the preload
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method. Much like a normal preload manager, it must be used on the same player
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instance that created it. It contains the loaded manifest, and stores the time of the video and last abr estimates. |