From 006de0ccbb2237ad240058bbe35300452c49e2ce Mon Sep 17 00:00:00 2001
From: stefangehrer <125955242+stefangehrer@users.noreply.github.com>
Date: Wed, 29 Jan 2025 09:42:20 +0100
Subject: [PATCH] fix: Fix AC-3 playback on Tizen 3.0 devices (#7969)

Fixes https://github.com/shaka-project/shaka-player/issues/7955
---
 lib/media/content_workarounds.js       | 78 ++++++++++++++++++++++++++
 lib/media/media_source_engine.js       | 13 +++++
 lib/util/platform.js                   | 13 +++++
 lib/util/stream_utils.js               |  5 ++
 test/media/media_source_engine_unit.js |  6 ++
 5 files changed, 115 insertions(+)

diff --git a/lib/media/content_workarounds.js b/lib/media/content_workarounds.js
index 6f4b1f7d70..424b04e0cd 100644
--- a/lib/media/content_workarounds.js
+++ b/lib/media/content_workarounds.js
@@ -347,6 +347,52 @@ 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;
+  }
 };
 
 /**
@@ -482,3 +528,35 @@ 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;
diff --git a/lib/media/media_source_engine.js b/lib/media/media_source_engine.js
index ff1747e07d..632ee5a1b6 100644
--- a/lib/media/media_source_engine.js
+++ b/lib/media/media_source_engine.js
@@ -614,6 +614,11 @@ 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) {
@@ -2096,6 +2101,14 @@ 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;
   }
 
diff --git a/lib/util/platform.js b/lib/util/platform.js
index 1039a057ac..ce35ff7cb9 100644
--- a/lib/util/platform.js
+++ b/lib/util/platform.js
@@ -636,6 +636,19 @@ 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".
    *
diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
index 252f9fca32..9243fb0065 100644
--- a/lib/util/stream_utils.js
+++ b/lib/util/stream_utils.js
@@ -1051,6 +1051,11 @@ shaka.util.StreamUtils = class {
       }
     }
 
+    if (codecs.toLowerCase() == 'ac-3' &&
+        shaka.util.Platform.requiresEC3InitSegments()) {
+      return 'ec-3';
+    }
+
     return codecs;
   }
 
diff --git a/test/media/media_source_engine_unit.js b/test/media/media_source_engine_unit.js
index 67c4c81313..562f554c2d 100644
--- a/test/media/media_source_engine_unit.js
+++ b/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);
 
@@ -544,6 +549,7 @@ describe('MediaSourceEngine', () => {
 
   describe('appendBuffer', () => {
     beforeEach(async () => {
+      requiresEC3InitSegments.and.returnValue(false);
       captureEvents(audioSourceBuffer, ['updateend', 'error']);
       captureEvents(videoSourceBuffer, ['updateend', 'error']);
       const initObject = new Map();