feat(offline): improve the speed of offline downloads (#4168)

Add the possibility to configure the number of downloads in parallel per stream. If you put a higher value the download time can decrease.

Related to #4166

Co-authored-by: Joey Parrish <[email protected]>

demo/common/message_ids.js

@@ -223,6 +223,7 @@ shakaDemo.MessageIds = {
   NUMBER_INTEGER_WARNING: 'DEMO_NUMBER_INTEGER_WARNING',
   NUMBER_NONZERO_DECIMAL_WARNING: 'DEMO_NUMBER_NONZERO_DECIMAL_WARNING',
   NUMBER_NONZERO_INTEGER_WARNING: 'DEMO_NUMBER_NONZERO_INTEGER_WARNING',
+  NUMBER_OF_PARALLEL_DOWNLOADS: 'DEMO_NUMBER_OF_PARALLEL_DOWNLOADS',
   OFFLINE_SECTION_HEADER: 'DEMO_OFFLINE_SECTION_HEADER',
   PREFER_FORCED_SUBS: 'DEMO_PREFER_FORCED_SUBS',
   PREFER_NATIVE_HLS: 'DEMO_PREFER_NATIVE_HLS',

demo/config.js

@@ -341,7 +341,9 @@ shakaDemo.Config = class {
     const docLink = this.resolveExternLink_('.OfflineConfiguration');
     this.addSection_(MessageIds.OFFLINE_SECTION_HEADER, docLink)
         .addBoolInput_(MessageIds.USE_PERSISTENT_LICENSES,
-            'offline.usePersistentLicense');
+            'offline.usePersistentLicense')
+        .addNumberInput_(MessageIds.NUMBER_OF_PARALLEL_DOWNLOADS,
+            'offline.numberOfParallelDownloads');
   }
 
   /** @private */

demo/locales/en.json

@@ -159,6 +159,7 @@
   "DEMO_NUMBER_INTEGER_WARNING": "Must be a positive integer.",
   "DEMO_NUMBER_NONZERO_DECIMAL_WARNING": "Must be a positive, nonzero number.",
   "DEMO_NUMBER_NONZERO_INTEGER_WARNING": "Must be a positive, nonzero integer.",
+  "DEMO_NUMBER_OF_PARALLEL_DOWNLOADS": "Number of parallel downloads",
   "DEMO_OBSERVE_QUALITY_CHANGES": "Observe media quality changes",
   "DEMO_OFFLINE": "Downloadable",
   "DEMO_OFFLINE_SEARCH": "Filters for assets that can be stored offline.",

demo/locales/source.json

@@ -639,6 +639,10 @@
     "description": "A warning on number inputs, telling the user what the expected input format is.",
     "message": "Must be a positive, nonzero integer."
   },
+  "DEMO_NUMBER_OF_PARALLEL_DOWNLOADS": {
+    "description": "The name of a configuration value.",
+    "message": "Number of parallel downloads."
+  },
   "DEMO_OBSERVE_QUALITY_CHANGES": {
     "description": "The name of a configuration value.",
     "message": "Observe media quality changes"

demo/main.js

@@ -582,7 +582,10 @@ shakaDemo.Main = class {
         };
         asset.storedProgress = 0;
         this.dispatchEventWithName_('shaka-main-offline-progress');
+        const start = Date.now();
         const stored = await storage.store(asset.manifestUri, metadata).promise;
+        const end = Date.now();
+        console.log('Download time:', end - start);
         asset.storedContent = stored;
       } catch (error) {
         this.onError_(/** @type {!shaka.util.Error} */ (error));

externs/shaka/player.js

@@ -1075,7 +1075,8 @@ shaka.extern.CmcdConfiguration;
  *       function(shaka.extern.TrackList):!Promise<shaka.extern.TrackList>,
  *   downloadSizeCallback: function(number):!Promise<boolean>,
  *   progressCallback: function(shaka.extern.StoredContent,number),
- *   usePersistentLicense: boolean
+ *   usePersistentLicense: boolean,
+ *   numberOfParallelDownloads: number
  * }}
  *
  * @property {function(shaka.extern.TrackList):!Promise<shaka.extern.TrackList>}
@@ -1098,6 +1099,11 @@ shaka.extern.CmcdConfiguration;
  *   license.  A network will be required to retrieve a temporary license to
  *   view.
  *   Defaults to <code>true</code>.
+ * @property {number} numberOfParallelDownloads
+ *   Number of parallel downloads.
+ *   Note: normally browsers limit to 5 request in parallel, so putting a
+ *   number higher than this will not help it download faster.
+ *   Defaults to <code>5</code>.
  * @exportDoc
  */
 shaka.extern.OfflineConfiguration;

lib/offline/storage.js

@@ -1324,6 +1324,9 @@ shaka.offline.Storage = class {
     const startTime =
         manifest.presentationTimeline.getSegmentAvailabilityStart();
 
+    const numberOfParallelDownloads = config.offline.numberOfParallelDownloads;
+    let groupId = 0;
+
     shaka.offline.Storage.forEachSegment_(stream, startTime, (segment) => {
       const pendingSegmentRefId =
           shaka.offline.DownloadInfo.idForSegmentRef(segment);
@@ -1337,7 +1340,7 @@ shaka.offline.Storage = class {
         const segmentDownload = new shaka.offline.DownloadInfo(
             segment,
             estimateId,
-            stream.id,
+            groupId,
             /* isInitSegment= */ false);
         toDownload.set(pendingSegmentRefId, segmentDownload);
       }
@@ -1352,7 +1355,7 @@ shaka.offline.Storage = class {
           const initDownload = new shaka.offline.DownloadInfo(
               segment.initSegmentReference,
               estimateId,
-              stream.id,
+              groupId,
               /* isInitSegment= */ true);
           toDownload.set(pendingInitSegmentRefId, initDownload);
         }
@@ -1372,6 +1375,7 @@ shaka.offline.Storage = class {
         dataKey: 0,
       };
       streamDb.segments.push(segmentDB);
+      groupId = (groupId + 1) % numberOfParallelDownloads;
     });
 
     return streamDb;

lib/util/player_configuration.js

@@ -222,6 +222,8 @@ shaka.util.PlayerConfiguration = class {
       // unexpected behaviours when someone tries to plays downloaded content
       // without a persistent license.
       usePersistentLicense: true,
+
+      numberOfParallelDownloads: 5,
     };
 
     const abr = {

test/offline/storage_integration.js

@@ -1110,10 +1110,7 @@ filterDescribe('Storage', storageSupport, () => {
           aRequestIsStarted.resolve();
           await promise;
 
-          // All downloads for a given stream are in the same "download group",
-          // and will be downloaded sequentially. Thus, we expect only the first
-          // download to be aborted.
-          expect(abortCheck()).toBe(i == 0 ? true : false);
+          expect(abortCheck()).toBe(true);
 
           return new ArrayBuffer(16);
         });