diff --git a/FFmpegKit b/FFmpegKit
index 86afd7287..7340b3242 160000
--- a/FFmpegKit
+++ b/FFmpegKit
@@ -1 +1 @@
-Subproject commit 86afd7287945a1789072439c2ab12be487d1a133
+Subproject commit 7340b3242320d69b13f89e5cf7e771d7369138a6
diff --git a/Sources/KSPlayer/AVPlayer/KSPictureInPictureController.swift b/Sources/KSPlayer/AVPlayer/KSPictureInPictureController.swift
index 2ad783f5b..b54e45854 100644
--- a/Sources/KSPlayer/AVPlayer/KSPictureInPictureController.swift
+++ b/Sources/KSPlayer/AVPlayer/KSPictureInPictureController.swift
@@ -57,6 +57,10 @@ public class KSPictureInPictureController: AVPictureInPictureController {
         startPictureInPicture()
         delegate = view
         guard KSOptions.isPipPopViewController else {
+            #if canImport(UIKit)
+            // 直接退到后台
+            UIControl().sendAction(#selector(URLSessionTask.suspend), to: UIApplication.shared, for: nil)
+            #endif
             return
         }
         self.view = view
diff --git a/Sources/KSPlayer/MEPlayer/FFmpegDecode.swift b/Sources/KSPlayer/MEPlayer/FFmpegDecode.swift
index 03b7f674a..9096940b2 100644
--- a/Sources/KSPlayer/MEPlayer/FFmpegDecode.swift
+++ b/Sources/KSPlayer/MEPlayer/FFmpegDecode.swift
@@ -61,7 +61,6 @@ class FFmpegDecode: DecodeProtocol {
                        let subtitle = closedCaptionsTrack.subtitle
                     {
                         let closedCaptionsPacket = Packet()
-                        closedCaptionsPacket.assetTrack = closedCaptionsTrack
                         if let corePacket = packet.corePacket {
                             closedCaptionsPacket.corePacket?.pointee.pts = corePacket.pointee.pts
                             closedCaptionsPacket.corePacket?.pointee.dts = corePacket.pointee.dts
@@ -74,7 +73,7 @@ class FFmpegDecode: DecodeProtocol {
                         let buffer = av_buffer_ref(sideData.pointee.buf)
                         closedCaptionsPacket.corePacket?.pointee.data = buffer?.pointee.data
                         closedCaptionsPacket.corePacket?.pointee.buf = buffer
-                        closedCaptionsPacket.fill()
+                        closedCaptionsPacket.assetTrack = closedCaptionsTrack
                         subtitle.putPacket(packet: closedCaptionsPacket)
                     }
                     if let sideData = av_frame_get_side_data(avframe, AV_FRAME_DATA_SEI_UNREGISTERED) {
diff --git a/Sources/KSPlayer/MEPlayer/MEPlayerItem.swift b/Sources/KSPlayer/MEPlayer/MEPlayerItem.swift
index 8c442e39b..1005eb086 100644
--- a/Sources/KSPlayer/MEPlayer/MEPlayerItem.swift
+++ b/Sources/KSPlayer/MEPlayer/MEPlayerItem.swift
@@ -544,7 +544,6 @@ extension MEPlayerItem {
             if corePacket.pointee.size <= 0 {
                 return 0
             }
-            packet.fill()
             let first = assetTracks.first { $0.trackID == corePacket.pointee.stream_index }
             if let first, first.isEnabled {
                 packet.assetTrack = first
diff --git a/Sources/KSPlayer/MEPlayer/Model.swift b/Sources/KSPlayer/MEPlayer/Model.swift
index c966c1c8e..2dd24a6ff 100644
--- a/Sources/KSPlayer/MEPlayer/Model.swift
+++ b/Sources/KSPlayer/MEPlayer/Model.swift
@@ -50,6 +50,7 @@ protocol MEPlayerDelegate: AnyObject {
 // MARK: protocol
 
 public protocol ObjectQueueItem {
+    var timebase: Timebase { get }
     var timestamp: Int64 { get set }
     var duration: Int64 { get set }
     // byte position
@@ -57,6 +58,11 @@ public protocol ObjectQueueItem {
     var size: Int32 { get set }
 }
 
+extension ObjectQueueItem {
+    var seconds: TimeInterval { cmtime.seconds }
+    var cmtime: CMTime { timebase.cmtime(for: timestamp) }
+}
+
 public protocol FrameOutput: AnyObject {
     var renderSource: OutputRenderSourceDelegate? { get set }
     func pause()
@@ -67,11 +73,6 @@ protocol MEFrame: ObjectQueueItem {
     var timebase: Timebase { get set }
 }
 
-extension MEFrame {
-    var seconds: TimeInterval { cmtime.seconds }
-    var cmtime: CMTime { timebase.cmtime(for: timestamp) }
-}
-
 // MARK: model
 
 // for MEPlayer
@@ -196,8 +197,11 @@ final class Packet: ObjectQueueItem {
     var timestamp: Int64 = 0
     var position: Int64 = 0
     var size: Int32 = 0
-    var assetTrack: FFmpegAssetTrack!
     private(set) var corePacket = av_packet_alloc()
+    var timebase: Timebase {
+        assetTrack.timebase
+    }
+
     var isKeyFrame: Bool {
         if let corePacket {
             return corePacket.pointee.flags & AV_PKT_FLAG_KEY == AV_PKT_FLAG_KEY
@@ -206,18 +210,16 @@ final class Packet: ObjectQueueItem {
         }
     }
 
-    var seconds: Double {
-        assetTrack.timebase.cmtime(for: position).seconds
-    }
-
-    func fill() {
-        guard let corePacket else {
-            return
+    var assetTrack: FFmpegAssetTrack! {
+        didSet {
+            guard let packet = corePacket?.pointee else {
+                return
+            }
+            timestamp = packet.pts == Int64.min ? packet.dts : packet.pts
+            position = packet.pos
+            duration = packet.duration
+            size = packet.size
         }
-        timestamp = corePacket.pointee.pts == Int64.min ? corePacket.pointee.dts : corePacket.pointee.pts
-        position = corePacket.pointee.pos
-        duration = corePacket.pointee.duration
-        size = corePacket.pointee.size
     }
 
     deinit {
diff --git a/Sources/KSPlayer/Metal/PixelBufferProtocol.swift b/Sources/KSPlayer/Metal/PixelBufferProtocol.swift
index ac5f38844..766daf6cf 100644
--- a/Sources/KSPlayer/Metal/PixelBufferProtocol.swift
+++ b/Sources/KSPlayer/Metal/PixelBufferProtocol.swift
@@ -230,7 +230,7 @@ class PixelBuffer: PixelBufferProtocol {
                 let contents = buffer?.contents()
                 let source = bytes[i]!
                 var j = 0
-                // while 的性能比for in快。
+                // 性能 while > stride(from:to:by:) > for in
                 while j < height {
                     contents?.advanced(by: j * size).copyMemory(from: source.advanced(by: j * byteCount), byteCount: byteCount)
                     j += 1