--- a/dom/media/mediasource/ContainerParser.cpp
+++ b/dom/media/mediasource/ContainerParser.cpp
@@ -172,16 +172,26 @@ public:
       return true;
     }
     // 0x1c53bb6b // Cues
     if (aData->Length() >= 4 &&
         (*aData)[0] == 0x1c && (*aData)[1] == 0x53 && (*aData)[2] == 0xbb &&
         (*aData)[3] == 0x6b) {
       return true;
     }
+    // 0xa3 // SimpleBlock
+    if (aData->Length() >= 1 &&
+        (*aData)[0] == 0xa3) {
+      return true;
+    }
+    // 0xa1 // Block
+    if (aData->Length() >= 1 &&
+        (*aData)[0] == 0xa1) {
+      return true;
+    }
     return false;
   }
 
   bool ParseStartAndEndTimestamps(MediaByteBuffer* aData,
                                   int64_t& aStart, int64_t& aEnd) override
   {
     bool initSegment = IsInitSegmentPresent(aData);
     if (initSegment) {