diff --git a/Examples/iOS/Preference.swift b/Examples/iOS/Preference.swift
index dc513191e..bdf723fb9 100644
--- a/Examples/iOS/Preference.swift
+++ b/Examples/iOS/Preference.swift
@@ -2,6 +2,6 @@ struct Preference: Sendable {
     // Temp
     static nonisolated(unsafe) var `default` = Preference()
 
-    var uri: String? = "rtmp://192.168.1.6/live"
+    var uri: String? = "rtmp://192.168.1.4/live"
     var streamName: String? = "live"
 }
diff --git a/HaishinKit.xcodeproj/project.pbxproj b/HaishinKit.xcodeproj/project.pbxproj
index de968c906..c1150c499 100644
--- a/HaishinKit.xcodeproj/project.pbxproj
+++ b/HaishinKit.xcodeproj/project.pbxproj
@@ -191,6 +191,7 @@
 		BC558268240BB40E00011AC0 /* RTMPStreamInfo.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC558267240BB40E00011AC0 /* RTMPStreamInfo.swift */; };
 		BC562DC7295767860048D89A /* AVCaptureDevice+Extension.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC562DC6295767860048D89A /* AVCaptureDevice+Extension.swift */; };
 		BC562DCB29576D220048D89A /* AVCaptureSession.Preset+Extension.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC562DCA29576D220048D89A /* AVCaptureSession.Preset+Extension.swift */; };
+		BC56452C2C4972BD00CC79C5 /* CMSampleBuffer+ExtensionTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC56452B2C4972BD00CC79C5 /* CMSampleBuffer+ExtensionTests.swift */; };
 		BC56765B2AD2AED800524F7E /* AudioCapture.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC56765A2AD2AED800524F7E /* AudioCapture.swift */; };
 		BC570B4828E9ACC10098A12C /* IOUnit.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC570B4728E9ACC10098A12C /* IOUnit.swift */; };
 		BC5A945C2BC2A8D80006F722 /* FLVFoundation.swift in Sources */ = {isa = PBXBuildFile; fileRef = BC5A945B2BC2A8D80006F722 /* FLVFoundation.swift */; };
@@ -669,6 +670,7 @@
 		BC558267240BB40E00011AC0 /* RTMPStreamInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RTMPStreamInfo.swift; sourceTree = "<group>"; };
 		BC562DC6295767860048D89A /* AVCaptureDevice+Extension.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "AVCaptureDevice+Extension.swift"; sourceTree = "<group>"; };
 		BC562DCA29576D220048D89A /* AVCaptureSession.Preset+Extension.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "AVCaptureSession.Preset+Extension.swift"; sourceTree = "<group>"; };
+		BC56452B2C4972BD00CC79C5 /* CMSampleBuffer+ExtensionTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "CMSampleBuffer+ExtensionTests.swift"; sourceTree = "<group>"; };
 		BC56765A2AD2AED800524F7E /* AudioCapture.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AudioCapture.swift; sourceTree = "<group>"; };
 		BC570B4728E9ACC10098A12C /* IOUnit.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IOUnit.swift; sourceTree = "<group>"; };
 		BC5A945B2BC2A8D80006F722 /* FLVFoundation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FLVFoundation.swift; sourceTree = "<group>"; };
@@ -1247,6 +1249,7 @@
 		BC03945D2AA8AFDD006EDE38 /* Extension */ = {
 			isa = PBXGroup;
 			children = (
+				BC56452B2C4972BD00CC79C5 /* CMSampleBuffer+ExtensionTests.swift */,
 				BC03945E2AA8AFF5006EDE38 /* ExpressibleByIntegerLiteral+ExtensionTests.swift */,
 			);
 			path = Extension;
@@ -1980,6 +1983,7 @@
 				290EA8A91DFB61E700053022 /* ByteArrayTests.swift in Sources */,
 				BC0587C12BD2A123006751C8 /* IOAudioMixerBySingleTrackTests.swift in Sources */,
 				295018221FFA1C9D00358E10 /* CMAudioSampleBufferFactory.swift in Sources */,
+				BC56452C2C4972BD00CC79C5 /* CMSampleBuffer+ExtensionTests.swift in Sources */,
 				BC7C56C329A1F28700C41A9B /* TSReaderTests.swift in Sources */,
 				BC7C56D129A78D4F00C41A9B /* ADTSHeaderTests.swift in Sources */,
 				BC3E384429C216BB007CD972 /* ADTSReaderTests.swift in Sources */,
diff --git a/Sources/Extension/CMSampleBuffer+Extension.swift b/Sources/Extension/CMSampleBuffer+Extension.swift
index 322efdaed..0a4c2f923 100644
--- a/Sources/Extension/CMSampleBuffer+Extension.swift
+++ b/Sources/Extension/CMSampleBuffer+Extension.swift
@@ -5,13 +5,13 @@ import CoreMedia
 extension CMSampleBuffer {
     @inlinable @inline(__always) var isNotSync: Bool {
         get {
-            guard sampleAttachments.isEmpty else {
+            guard !sampleAttachments.isEmpty else {
                 return false
             }
             return sampleAttachments[0][.notSync] != nil
         }
         set {
-            guard sampleAttachments.isEmpty else {
+            guard !sampleAttachments.isEmpty else {
                 return
             }
             sampleAttachments[0][.notSync] = newValue ? 1 : nil
diff --git a/Tests/Extension/CMSampleBuffer+ExtensionTests.swift b/Tests/Extension/CMSampleBuffer+ExtensionTests.swift
new file mode 100644
index 000000000..c41df464c
--- /dev/null
+++ b/Tests/Extension/CMSampleBuffer+ExtensionTests.swift
@@ -0,0 +1,21 @@
+import Foundation
+import XCTest
+import CoreMedia
+
+@testable import HaishinKit
+
+final class CMSampleBufferExtensionTests: XCTestCase {
+    func testIsNotSync() {
+        if let video1 = CMVideoSampleBufferFactory.makeSampleBuffer(width: 100, height: 100) {
+            video1.sampleAttachments[0][.notSync] = 1
+        } else {
+            XCTFail()
+        }
+
+        if let video2 = CMVideoSampleBufferFactory.makeSampleBuffer(width: 100, height: 100) {
+            XCTAssertFalse(video2.isNotSync)
+        } else {
+            XCTFail()
+        }
+    }
+}