diff --git a/isoparser/src/main/java/org/mp4parser/RewindableReadableByteChannel.java b/isoparser/src/main/java/org/mp4parser/RewindableReadableByteChannel.java
index 10d10da4d..1bf7945de 100644
--- a/isoparser/src/main/java/org/mp4parser/RewindableReadableByteChannel.java
+++ b/isoparser/src/main/java/org/mp4parser/RewindableReadableByteChannel.java
@@ -78,6 +78,12 @@ public void rewind() {
         nextBufferReadPosition = 0;
     }
 
+    // for isoviewer
+    public ReadableByteChannel underlyingChannel()
+    {
+        return readableByteChannel;
+    }
+
     /**
      * @see ReadableByteChannel#isOpen()
      */