fix: Fix AC-3 playback on Tizen 3.0 devices (#7969)

Fixes #7955

Author: stefangehrer

lib/media/content_workarounds.js

@@ -335,6 +335,52 @@ shaka.media.ContentWorkarounds = class {
       boxView.setUint32(ContentWorkarounds.BOX_SIZE_OFFSET_, newBoxSize);
     }
   }
+
+  /**
+   * Transform the init segment into a new init segment buffer that indicates
+   * EC-3 as audio codec instead of AC-3. Even though any EC-3 decoder should
+   * be able to decode AC-3 streams, there are platforms that do not accept
+   * AC-3 as codec.
+   *
+   * Should only be called for MP4 init segments, and only on platforms that
+   * need this workaround. Returns a new buffer containing the modified init
+   * segment.
+   *
+   * @param {!BufferSource} initSegmentBuffer
+   * @return {!Uint8Array}
+   */
+  static fakeEC3(initSegmentBuffer) {
+    const ContentWorkarounds = shaka.media.ContentWorkarounds;
+    const initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
+    const ancestorBoxes = [];
+
+    const onSimpleAncestorBox = (box) => {
+      ancestorBoxes.push({start: box.start, size: box.size});
+      shaka.util.Mp4Parser.children(box);
+    };
+
+    new shaka.util.Mp4Parser()
+        .box('moov', onSimpleAncestorBox)
+        .box('trak', onSimpleAncestorBox)
+        .box('mdia', onSimpleAncestorBox)
+        .box('minf', onSimpleAncestorBox)
+        .box('stbl', onSimpleAncestorBox)
+        .box('stsd', (box) => {
+          ancestorBoxes.push({start: box.start, size: box.size});
+          const stsdBoxView = shaka.util.BufferUtils.toDataView(
+              initSegment, box.start);
+          for (let i=0; i<box.size; i++) {
+            const codecTag = stsdBoxView.getUint32(i);
+            if (codecTag == ContentWorkarounds.BOX_TYPE_AC_3_) {
+              stsdBoxView.setUint32(i, ContentWorkarounds.BOX_TYPE_EC_3_);
+            } else if (codecTag == ContentWorkarounds.BOX_TYPE_DAC3_) {
+              stsdBoxView.setUint32(i, ContentWorkarounds.BOX_TYPE_DEC3_);
+            }
+          }
+        }).parse(initSegment);
+
+    return initSegment;
+  }
 };
 
 /**
@@ -470,3 +516,35 @@ shaka.media.ContentWorkarounds.BOX_TYPE_ENCV_ = 0x656e6376;
  * @private
  */
 shaka.media.ContentWorkarounds.BOX_TYPE_ENCA_ = 0x656e6361;
+
+/**
+ * Box type for "ac-3".
+ *
+ * @const {number}
+ * @private
+ */
+shaka.media.ContentWorkarounds.BOX_TYPE_AC_3_ = 0x61632d33;
+
+/**
+ * Box type for "dac3".
+ *
+ * @const {number}
+ * @private
+ */
+shaka.media.ContentWorkarounds.BOX_TYPE_DAC3_ = 0x64616333;
+
+/**
+ * Box type for "ec-3".
+ *
+ * @const {number}
+ * @private
+ */
+shaka.media.ContentWorkarounds.BOX_TYPE_EC_3_ = 0x65632d33;
+
+/**
+ * Box type for "dec3".
+ *
+ * @const {number}
+ * @private
+ */
+shaka.media.ContentWorkarounds.BOX_TYPE_DEC3_ = 0x64656333;

lib/media/media_source_engine.js

@@ -543,6 +543,11 @@ shaka.media.MediaSourceEngine = class {
             stream, contentType),
         'Type negotiation should happen before MediaSourceEngine.init!');
 
+    if (contentType == ContentType.AUDIO && codecs) {
+      codecs = shaka.util.StreamUtils.getCorrectAudioCodecs(
+          codecs, stream.mimeType);
+    }
+
     let mimeType = shaka.util.MimeUtils.getFullType(
         stream.mimeType, codecs);
     if (contentType == ContentType.TEXT) {
@@ -1845,6 +1850,14 @@ shaka.media.MediaSourceEngine = class {
       segment = shaka.media.ContentWorkarounds.fakeEncryption(segment, uri);
     }
 
+    if (isInitSegment &&
+        Platform.requiresEC3InitSegments() &&
+        shaka.util.MimeUtils.getContainerType(
+            this.sourceBufferTypes_[contentType]) == 'mp4') {
+      shaka.log.debug('Forcing fake EC-3 information in init segment.');
+      segment = shaka.media.ContentWorkarounds.fakeEC3(segment);
+    }
+
     return segment;
   }
 

lib/util/platform.js

@@ -621,6 +621,19 @@ shaka.util.Platform = class {
       (Platform.isEdge() && Platform.isWindows() && isPlayReady);
   }
 
+  /**
+   * Returns true if the platform requires AC-3 signalling in init
+   * segments to be replaced with EC-3 signalling.
+   * For such platforms, MediaSourceEngine will attempt to work
+   * around it by inserting fake EC-3 signalling into
+   * initialization segments.
+   *
+   * @return {boolean}
+   */
+  static requiresEC3InitSegments() {
+    return shaka.util.Platform.isTizen3();
+  }
+
   /**
    * Returns true if the platform supports SourceBuffer "sequence mode".
    *

lib/util/stream_utils.js

@@ -996,6 +996,11 @@ shaka.util.StreamUtils = class {
       }
     }
 
+    if (codecs.toLowerCase() == 'ac-3' &&
+        shaka.util.Platform.requiresEC3InitSegments()) {
+      return 'ec-3';
+    }
+
     return codecs;
   }
 

test/media/media_source_engine_unit.js

@@ -125,6 +125,8 @@ describe('MediaSourceEngine', () => {
   /** @type {!jasmine.Spy} */
   let requiresEncryptionInfoInAllInitSegmentsSpy;
   /** @type {!jasmine.Spy} */
+  let requiresEC3InitSegments;
+  /** @type {!jasmine.Spy} */
   let fakeEncryptionSpy;
 
   /** @type {!shaka.media.MediaSourceEngine} */
@@ -214,6 +216,9 @@ describe('MediaSourceEngine', () => {
     requiresEncryptionInfoInAllInitSegmentsSpy = spyOn(shaka.util.Platform,
         'requiresEncryptionInfoInAllInitSegments').and.returnValue(false);
 
+    requiresEC3InitSegments = spyOn(shaka.util.Platform,
+        'requiresEC3InitSegments').and.returnValue(false);
+
     fakeEncryptionSpy = spyOn(shaka.media.ContentWorkarounds, 'fakeEncryption')
         .and.callFake((data) => data + 100);
 
@@ -540,6 +545,7 @@ describe('MediaSourceEngine', () => {
 
   describe('appendBuffer', () => {
     beforeEach(async () => {
+      requiresEC3InitSegments.and.returnValue(false);
       captureEvents(audioSourceBuffer, ['updateend', 'error']);
       captureEvents(videoSourceBuffer, ['updateend', 'error']);
       const initObject = new Map();