feat: Add callback for apps to pre-process DASH manifests (shaka-proj…

…ect#3480)

Added support for efficient preprocessing of DASH manifest after they have been parsed into an XMLDocument

This is configured with the new manifest.dash.manifestPreprocessor setting.

This is need to efficiently repair manifests that are not compatible with Shaka Player.

Closes shaka-project#3339

externs/shaka/player.js

@@ -634,7 +634,8 @@ shaka.extern.DrmConfiguration;
  *   ignoreSuggestedPresentationDelay: boolean,
  *   ignoreEmptyAdaptationSet: boolean,
  *   ignoreMaxSegmentDuration: boolean,
- *   keySystemsByURI: !Object.<string, string>
+ *   keySystemsByURI: !Object.<string, string>,
+ *   manifestPreprocessor: function(!Element)
  * }}
  *
  * @property {string} clockSyncUri
@@ -684,6 +685,10 @@ shaka.extern.DrmConfiguration;
  * @property {Object.<string, string>} keySystemsByURI
  *   A map of scheme URI to key system name. Defaults to default key systems
  *   mapping handled by Shaka.
+ * @property {function(!Element)} manifestPreprocessor
+ *   Called immediately after the DASH manifest has been parsed into an
+ *   XMLDocument. Provides a way for applications to perform efficient
+ *   preprocessing of the manifest.
  * @exportDoc
  */
 shaka.extern.DashManifestConfiguration;

lib/dash/dash_parser.js

@@ -289,6 +289,11 @@ shaka.dash.DashParser = class {
     const Functional = shaka.util.Functional;
     const XmlUtils = shaka.util.XmlUtils;
 
+    const manifestPreprocessor = this.config_.dash.manifestPreprocessor;
+    if (manifestPreprocessor) {
+      manifestPreprocessor(mpd);
+    }
+
     // Get any Location elements.  This will update the manifest location and
     // the base URI.
     /** @type {!Array.<string>} */

lib/util/player_configuration.js

@@ -109,6 +109,12 @@ shaka.util.PlayerConfiguration = class {
           'urn:uuid:f239e769-efa3-4850-9c16-a903c6932efb':
             'com.adobe.primetime',
         },
+        // Need some operation in the callback or else closure may remove calls
+        // to the function as it would be a no-op.  The operation can't just be
+        // a log message, because those are stripped in the compiled build.
+        manifestPreprocessor: (element) => {
+          return element;
+        },
       },
       hls: {
         ignoreTextStreamFailures: false,

test/dash/dash_parser_manifest_unit.js

@@ -1790,6 +1790,48 @@ describe('DashParser Manifest', () => {
     expect(manifest.presentationTimeline).toBeTruthy();
   });
 
+  it('Invokes manifestPreprocessor in config', async () => {
+    const manifestText = [
+      '<MPD minBufferTime="PT75S">',
+      '  <Period id="1" duration="PT30S">',
+      '    <AdaptationSet id="2" mimeType="video/mp4">',
+      '      <Representation id="video-sd" width="640" height="480">',
+      '        <BaseURL>v-sd.mp4</BaseURL>',
+      '        <SegmentBase indexRange="100-200" />',
+      '      </Representation>',
+      '    </AdaptationSet>',
+      '    <AdaptationSet id="3" mimeType="audio/mp4">',
+      '      <Representation id="audio-en">',
+      '        <BaseURL>a-en.mp4</BaseURL>',
+      '        <SegmentBase indexRange="100-200" />',
+      '      </Representation>',
+      '    </AdaptationSet>',
+      '    <AdaptationSet mimeType="text/vtt" lang="de">',
+      '      <Representation>',
+      '        <BaseURL>http://example.com/de.vtt</BaseURL>',
+      '      </Representation>',
+      '    </AdaptationSet>',
+      '  </Period>',
+      '</MPD>',
+    ].join('\n');
+
+    fakeNetEngine.setResponseText('dummy://foo', manifestText);
+    const config = shaka.util.PlayerConfiguration.createDefault().manifest;
+    config.dash.manifestPreprocessor = (mpd) => {
+      const selector = 'AdaptationSet[mimeType="text/vtt"';
+      const vttElements = mpd.querySelectorAll(selector);
+      for (const element of vttElements) {
+        element.parentNode.removeChild(element);
+      }
+    };
+    parser.configure(config);
+
+    /** @type {shaka.extern.Manifest} */
+    const manifest = await parser.start('dummy://foo', playerInterface);
+    const stream = manifest.textStreams[0];
+    expect(stream).toBeUndefined();
+  });
+
   it('converts Accessibility element to "kind"', async () => {
     const manifestText = [
       '<MPD minBufferTime="PT75S">',