Fall back to MediaSource.isTypeSupported() if cast APIs aren't availa…

…ble. Only throw an error if the entire cast namespace is unavailable.

lib/polyfill/media_capabilities.js

@@ -105,30 +105,22 @@ shaka.polyfill.MediaCapabilities = class {
         return res;
       }
       // Use 'MediaSource.isTypeSupported' to check if the stream is supported.
+      // Cast platforms will additionally check canDisplayType(), which
+      // accepts extended MIME type parameters.
+      // See: https://github.com/shaka-project/shaka-player/issues/4726
       if (videoConfig) {
         const contentType = videoConfig.contentType;
-        let isSupported = MediaSource.isTypeSupported(contentType);
+        let isSupported;
         if (shaka.util.Platform.isChromecast()) {
-          // Cast platforms will additionally check canDisplayType(), which
-          // accepts extended MIME type parameters.
-          // There will be at most 2 calls:
-          // - The first call determines the stability of
-          // the API by validating a contentType input limited only to MIME type
-          // and codecs is identical to MediaSource.isTypeSupported().
-          // - If the same result is observed, a second call will be executed
-          // containing resolution, frame rate, and transfer function support.
-          // See: https://github.com/shaka-project/shaka-player/issues/4726
-          if (isSupported ===
-              shaka.polyfill.MediaCapabilities.canCastDisplayType_({
-                contentType})) {
-            isSupported = shaka.polyfill.MediaCapabilities.canCastDisplayType_({
-              contentType,
-              width: videoConfig.width,
-              height: videoConfig.height,
-              frameRate: videoConfig.framerate,
-              transferFunction: videoConfig.transferFunction,
-            });
-          }
+          isSupported = shaka.polyfill.MediaCapabilities.canCastDisplayType_({
+            contentType,
+            width: videoConfig.width,
+            height: videoConfig.height,
+            frameRate: videoConfig.framerate,
+            transferFunction: videoConfig.transferFunction,
+          });
+        } else {
+          isSupported = MediaSource.isTypeSupported(contentType);
         }
         if (!isSupported) {
           return res;
@@ -269,14 +261,18 @@ shaka.polyfill.MediaCapabilities = class {
     frameRate = undefined,
     transferFunction = undefined,
   }) {
-    if (!(window.cast && cast.__platform__ &&
-          cast.__platform__.canDisplayType)) {
+    if (!(window.cast && cast)) {
       shaka.log.error('Expected cast namespace to be available!');
       throw new shaka.util.Error(
           shaka.util.Error.Severity.CRITICAL,
           shaka.util.Error.Category.CAST,
-          shaka.util.Error.Code.CAST_UNEXPECTED_PLATFORM);
+          shaka.util.Error.Code.CAST_API_UNAVAILABLE);
+    } else if (!(cast.__platform__ && cast.__platform__.canDisplayType)) {
+      shaka.log.warning('Expected cast APIs to be available! Falling back to ' +
+          'MediaSource.isTypeSupported() for type support.');
+      return MediaSource.isTypeSupported(contentType);
     }
+
     let displayType = contentType;
     if (width && height) {
       displayType += `; width=${width}; height=${height}`;

lib/util/error.js

@@ -932,13 +932,6 @@ shaka.util.Error.Code = {
    */
   'CAST_RECEIVER_APP_UNAVAILABLE': 8006,
 
-  /**
-   * The Cast platform namespace was expected to be available, but wasn't.
-   * <br> This may be caused by Shaka failing to identify the correct platform
-   * through the userAgent string.
-   */
-  'CAST_UNEXPECTED_PLATFORM': 8007,
-
 
   // RETIRED: CAST_RECEIVER_APP_ID_MISSING': 8007,
 

test/polyfill/media_capabilities_unit.js

@@ -6,12 +6,12 @@
 
 describe('MediaCapabilities', () => {
   const Util = shaka.test.Util;
+  const originalCast = window['cast'];
   const originalVendor = navigator.vendor;
   const originalUserAgent = navigator.userAgent;
   const originalRequestMediaKeySystemAccess =
     navigator.requestMediaKeySystemAccess;
   const originalMediaCapabilities = navigator.mediaCapabilities;
-  const originalCast = window['cast'];
 
   /** @type {MediaDecodingConfiguration} */
   let mockDecodingConfig;
@@ -182,16 +182,15 @@ describe('MediaCapabilities', () => {
           .toHaveBeenCalledTimes(1);
     });
 
-    it('fails when the cast namespace is not available', async () => {
-      // Mock Shaka throwing an error from identifying an unexpected, non-Cast
-      // platform when performing Cast logic.
+    it('throws when the cast namespace is not available', async () => {
+      // We don't set a mock cast namespace here to signal an error.
       const isChromecastSpy =
           spyOn(shaka['util']['Platform'],
               'isChromecast').and.returnValue(true);
       const expected = Util.jasmineError(new shaka.util.Error(
           shaka.util.Error.Severity.CRITICAL,
           shaka.util.Error.Category.CAST,
-          shaka.util.Error.Code.CAST_UNEXPECTED_PLATFORM));
+          shaka.util.Error.Code.CAST_API_UNAVAILABLE));
       const isTypeSupportedSpy =
           spyOn(window['MediaSource'], 'isTypeSupported').and.returnValue(true);
 
@@ -200,13 +199,33 @@ describe('MediaCapabilities', () => {
           navigator.mediaCapabilities.decodingInfo(mockDecodingConfig))
           .toBeRejectedWith(expected);
 
+      expect(isTypeSupportedSpy).not.toHaveBeenCalled();
       // 1 (during install()) + 1 (for video config check).
       expect(isChromecastSpy).toHaveBeenCalledTimes(2);
-      // Called for decodingConfig.audio. This is never reached because of the
-      // error throw.
-      expect(isTypeSupportedSpy).not.toHaveBeenCalled();
     });
 
+    it('falls back to isTypeSupported() when canDisplayType() missing',
+        async () => {
+          // We only set the cast namespace, but not the canDisplayType() API.
+          window['cast'] = {};
+          const isChromecastSpy =
+              spyOn(shaka['util']['Platform'],
+                  'isChromecast').and.returnValue(true);
+          const isTypeSupportedSpy =
+              spyOn(window['MediaSource'], 'isTypeSupported')
+                  .and.returnValue(true);
+
+          shaka.polyfill.MediaCapabilities.install();
+          await navigator.mediaCapabilities.decodingInfo(mockDecodingConfig);
+
+          expect(mockCanDisplayType).not.toHaveBeenCalled();
+          // 1 (during install()) + 1 (for video config check).
+          expect(isChromecastSpy).toHaveBeenCalledTimes(2);
+          // 1 (fallback in canCastDisplayType()) +
+          // 1 (mockDecodingConfig.audio).
+          expect(isTypeSupportedSpy).toHaveBeenCalledTimes(2);
+        });
+
     it('should use cast.__platform__.canDisplayType for "supported" field ' +
         'when platform is Cast', async () => {
       // We're using quotes to access window.cast because the compiler
@@ -241,10 +260,9 @@ describe('MediaCapabilities', () => {
 
       // 1 (during install()) + 1 (for video config check).
       expect(isChromecastSpy).toHaveBeenCalledTimes(2);
-      // Called once for mockDecodingConfig.audio. Resolution, frame rate, and
-      // EOTF aren't applicable for audio, so isTypeSupported() is sufficient.
+      // 1 (mockDecodingConfig.audio).
       expect(isTypeSupportedSpy).toHaveBeenCalledTimes(1);
-      // Called once for mockDecodingConfig.video.
+      // Called once in canCastDisplayType.
       expect(mockCanDisplayType).toHaveBeenCalledTimes(1);
     });
   });