Hello there, I need to move through video loaded in an AVPlayer one frame at a time back or forth. For that I tried to use AVPlayerItem's method step(byCount:) and it works just fine. However I need to know when stepping happened and as far as I observed it is not immediate using the method. If I check the currentTime() just after calling the method it's the same and if I do it slightly later (depending of the video itself) it shows the correct "jumped" time. To achieve my goal I tried subclassing AVPlayerItem and implement my own async method utilizing NotificationCenter and the timeJumpedNotification assuming it would deliver it as the time actually jumps but it's not the case. Here is my "stripped" and simplified version of the custom Player Item: import AVFoundation final class PlayerItem: AVPlayerItem { private var jumpCompletion: ( (CMTime) -> () )? override init(asset: AVAsset, automaticallyLoadedAssetKeys: [String]?) { super .init(asset: asset, automaticallyLoadedAssetKeys: automaticallyLoadedAssetKeys) NotificationCenter.default.addObserver(self, selector: #selector(timeDidChange(_:)), name: AVPlayerItem.timeJumpedNotification, object: self) } deinit { NotificationCenter.default.removeObserver(self, name: AVPlayerItem.timeJumpedNotification, object: self) jumpCompletion = nil } @discardableResult func step(by count: Int) async -> CMTime { await withCheckedContinuation { continuation in step(by: count) { time in continuation.resume(returning: time) } } } func step(by count: Int, completion: @escaping ( (CMTime) -> () )) { guard jumpCompletion == nil else { completion(currentTime()) return } jumpCompletion = completion step(byCount: count) } @objc private func timeDidChange(_ notification: Notification) { switch notification.name { case AVPlayerItem.timeJumpedNotification where notification.object as? AVPlayerItem [==](https://www.example.com/) self: jumpCompletion?(currentTime()) jumpCompletion = nil default: return } } } In short the notification never gets called thus the above is not working. I guess the key there is that in the docs about the timeJumpedNotification: is said: "A notification the system posts when a player item’s time changes discontinuously." so the step(byCount:) is not considered as discontinuous operation and doesn't trigger it. I'd be really helpful if somebody can help as I don't want to use seek(to:toleranceBefore:toleranceAfter:) mainly cause it's not accurate in terms of the exact next/previous frame as the video might have VFR and that causes repeating frames sometimes or even skipping one or another. Thanks a lot

I have AVPlayer with AVPictureInPictureController. Play video in app and picture In Picture works except one situation. Issue is: I pause video in application and during switch to background is not PiP activate. What do I wrong? import UIKit import AVKit import AVFoundation class ViewControllerSec: UIViewController,AVPictureInPictureControllerDelegate { var pipPlayer: AVPlayer! var avCanvas : UIView! var pipCanvas: AVPlayerLayer? var pipController: AVPictureInPictureController! var mainViewControler : UIViewController! var playerItem : AVPlayerItem! var videoAvasset : AVAsset! public func link(to parentViewController : UIViewController) { mainViewControler = parentViewController setup() } @objc func appWillResignActiveNotification(application: UIApplication) { guard let pipController = pipController else { print("PiP not supported") return } print("PIP isSuspend: \(pipController.isPictureInPictureSuspended)") print("PIP isPossible: \(pipController.isPictureInPicturePossible)" if playerItem.status == .readyToPlay { if pipPlayer.rate == 0 { pipPlayer.play() } pipController.startPictureInPicture(). ---> Errorin log: Failed to start picture in picture. } else { print("Player not ready for PiP.") } } private func setupAudio() { do { let session = AVAudioSession.sharedInstance() try session.setCategory(.playback, mode: .moviePlayback) try session.setActive(true) } catch { print("Audio session setup failed: \(error.localizedDescription)") } } @objc func playerItemDidFailToPlayToEnd(_ notification: Notification) { if let error = notification.userInfo?[AVPlayerItemFailedToPlayToEndTimeErrorKey] as? Error { print("Failed to play to end: \(error.localizedDescription)") } } func setup() { setupAudio() guard let videoURL = URL(string: "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.mp4/.m3u8") else { return } videoAvasset = AVAsset(url: videoURL) playerItem = AVPlayerItem(asset: videoAvasset) addPlayerObservers() pipPlayer = AVPlayer(playerItem: playerItem) avCanvas = UIView(frame: view.bounds) pipCanvas = AVPlayerLayer(player: pipPlayer) guard let pipCanvas else { return } pipCanvas.frame = avCanvas.bounds //pipCanvas.videoGravity = .resizeAspectFill mainViewControler.view.addSubview(avCanvas) avCanvas.layer.addSublayer(pipCanvas) if AVPictureInPictureController.isPictureInPictureSupported() { pipController = AVPictureInPictureController(playerLayer: pipCanvas) pipController?.delegate = self pipController?.canStartPictureInPictureAutomaticallyFromInline = true } let playButton = UIButton(frame: CGRect(x: 20, y: 50, width: 100, height: 50)) playButton.setTitle("Play", for: .normal) playButton.backgroundColor = .blue playButton.addTarget(self, action: #selector(playTapped), for: .touchUpInside) mainViewControler.view.addSubview(playButton) let pauseButton = UIButton(frame: CGRect(x: 140, y: 50, width: 100, height: 50)) pauseButton.setTitle("Pause", for: .normal) pauseButton.backgroundColor = .red pauseButton.addTarget(self, action: #selector(pauseTapped), for: .touchUpInside) mainViewControler.view.addSubview(pauseButton) let pipButton = UIButton(frame: CGRect(x: 260, y: 50, width: 150, height: 50)) pipButton.setTitle("Start PiP", for: .normal) pipButton.backgroundColor = .green pipButton.addTarget(self, action: #selector(startPictureInPicture), for: .touchUpInside) mainViewControler.view.addSubview(pipButton) print("Error:\(String(describing: pipPlayer.error?.localizedDescription))") NotificationCenter.default.addObserver(forName: UIApplication.didEnterBackgroundNotification, object: nil, queue: nil) { [weak self] _ in guard let self = self else { return } if self.pipPlayer.rate == 0 { self.pipPlayer.play() pipController?.startPictureInPicture() } } func addPlayerObservers() { playerItem?.addObserver(self, forKeyPath: "status", options: [.old, .new], context: nil) NotificationCenter.default.addObserver(self, selector: #selector(playerDidFinishPlaying(_:)), name: .AVPlayerItemDidPlayToEndTime, object: playerItem) } override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { if keyPath == "status" { if let statusNumber = change?[.newKey] as? NSNumber { let status = AVPlayer.Status(rawValue: statusNumber.intValue)! switch status { case .readyToPlay: print("Player is ready to play") case .failed: print("Player failed: \(String(describing: playerItem?.error))") case .unknown: print("Player status is unknown") @unknown default: fatalError() } } } } @objc func playerDidFinishPlaying(_ notification: Notification) { print("Video finished playing.") } deinit { playerItem?.removeObserver(self, forKeyPath: "status") NotificationCenter.default.removeObserver(self) } @objc func playTapped() { pipPlayer.play() } @objc func pauseTapped() { pipPlayer.pause() } @objc func startPictureInPicture() { if let pipController = pipController, !pipController.isPictureInPictureActive { pipController.startPictureInPicture() } } @objc func stopPictureInPicture() { if let pipController = pipController, pipController.isPictureInPictureActive { pipController.stopPictureInPicture() } } func pictureInPictureController(_ pictureInPictureController: AVPictureInPictureController, failedToStartPictureInPictureWithError error: Error) { print("Failed to start PiP: \(error.localizedDescription)") if let underlyingError = (error as NSError).userInfo[NSUnderlyingErrorKey] { print("Underlying error: \(underlyingError)") } } }

Hello, I’m experiencing an issue with video playback in my Javascript (SvelteKit) application using Capacitor. The video plays and loops correctly on Android and web browsers (including Safari) but stops unexpectedly after a few iterations on iOS native App. <video src={videoPath} autoplay muted loop playsinline class="h-auto w-full max-w-full object-cover"></video> Has anyone encountered a similar issue or have insights into what might be causing this behavior on iOS? Any suggestions or workarounds would be greatly appreciated. Maybe it has something to do with the iOS power saving policy? Thank you in advance for your help!

I have a SwiftUI app that needs to be able to receive photos and videos from the Photos app. When the user shares an item from the Photos app they can choose to share to a destination app. When doing so from the Files app, my app appears as a share destination and the .onOpenURL successfully handles the incoming content. The CFBundleTypeName and CFBundleTypeRole have been configured accordingly. What I don't understand is why I can share from the Files app and select my app as the destination, while not being able to select my app when sharing from the Photos app. What does the Photos app require to allow a given app to available as a share destination? I'd also like to be able to do this from other apps such as the YouTube app.

Hi I'm working on a project that require video frame PTS to be consistent between original video and a transcoded one. It's working fairly well on regular mp4, however if I set preferredOutputSegmentInterval to have generate a fMP4 output, even I specified the initialSegmentStartTime as 0, it always add one frame pts offset to all frames. For example: if I use the code sample provided by Apple: https://developer.apple.com/videos/play/wwdc2020/10011/?time=406, useffprobe -select_streams v:0 -show_entries packet=pts_time -of csv ~/Downloads/fmp4/prog_index.m3u8 to display the pts of the output, it doesn't start from 0, but has some one frame pts offset. I also tried open with MP4Box, it also shows the first frames dts and cts are not start from 0. However, if I use AVAssetReader to read the same output video, and get the PTS from 1st frame, it's returning 0. So I can't use it to calculate the pts difference between 2 videos neither. Can I get some help to understand why there is difference between AVAssetWriter/Reader fMP4's pts and others like ffprobe?

Hi, I'm trying to decode a HLS livestream with VideoToolbox. The CMSampleBuffer is successfully created (OSStatus == noErr). When I enqueue the CMSampleBuffer to a AVSampleBufferDisplayLayer the view isn't displaying anything and the status of the AVSampleBufferDisplayLayer is 1 (rendering). When I use a VTDecompressionSession to convert the CMSampleBuffer to a CVPixelBuffer the VTDecompressionOutputCallback returns a -8969 (bad data error). What do I need to fix in my code? Do I incorrectly parse the data from the segment for the CMSampleBuffer? let segmentData = try await downloadSegment(from: segment.url) let (sps, pps, idr) = try parseH264FromTSSegment(tsData: segmentData) if self.formatDescription == nil { self.formatDescription = try CMFormatDescription(h264ParameterSets: [sps, pps]) } if let sampleBuffer = try createSampleBuffer(from: idr, segment: segment) { try self.decodeSampleBuffer(sampleBuffer) } func parseH264FromTSSegment(tsData: Data) throws -> (sps: Data, pps: Data, idr: Data) { let tsSize = 188 var pesData = Data() for i in stride(from: 0, to: tsData.count, by: tsSize) { let tsPacket = tsData.subdata(in: i..<min(i + tsSize, tsData.count)) guard let payload = extractPayloadFromTSPacket(tsPacket) else { continue } pesData.append(payload) } let nalUnits = parseNalUnits(from: pesData) var sps: Data? var pps: Data? var idr: Data? for nalUnit in nalUnits { guard let firstByte = nalUnit.first else { continue } let nalType = firstByte & 0x1F switch nalType { case 7: // SPS sps = nalUnit case 8: // PPS pps = nalUnit case 5: // IDR idr = nalUnit default: break } if sps != nil, pps != nil, idr != nil { break } } guard let validSPS = sps, let validPPS = pps, let validIDR = idr else { throw NSError() } return (validSPS, validPPS, validIDR) } func extractPayloadFromTSPacket(_ tsPacket: Data) -> Data? { let syncByte: UInt8 = 0x47 guard tsPacket.count == 188, tsPacket[0] == syncByte else { return nil } let payloadStart = (tsPacket[1] & 0x40) != 0 let adaptationFieldControl = (tsPacket[3] & 0x30) >> 4 var payloadOffset = 4 if adaptationFieldControl == 2 || adaptationFieldControl == 3 { let adaptationFieldLength = Int(tsPacket[4]) payloadOffset += 1 + adaptationFieldLength } guard adaptationFieldControl == 1 || adaptationFieldControl == 3 else { return nil } let payload = tsPacket.subdata(in: payloadOffset..<tsPacket.count) return payloadStart ? payload : nil } func parseNalUnits(from h264Data: Data) -> [Data] { let startCode = Data([0x00, 0x00, 0x00, 0x01]) var nalUnits: [Data] = [] var searchRange = h264Data.startIndex..<h264Data.endIndex while let range = h264Data.range(of: startCode, options: [], in: searchRange) { let nextStart = h264Data.range(of: startCode, options: [], in: range.upperBound..<h264Data.endIndex)?.lowerBound ?? h264Data.endIndex let nalUnit = h264Data.subdata(in: range.upperBound..<nextStart) nalUnits.append(nalUnit) searchRange = nextStart..<h264Data.endIndex } return nalUnits } private func createSampleBuffer(from data: Data, segment: HLSSegment) throws -> CMSampleBuffer? { var blockBuffer: CMBlockBuffer? let alignedData = UnsafeMutableRawPointer.allocate(byteCount: data.count, alignment: MemoryLayout<UInt8>.alignment) data.copyBytes(to: alignedData.assumingMemoryBound(to: UInt8.self), count: data.count) let blockStatus = CMBlockBufferCreateWithMemoryBlock( allocator: kCFAllocatorDefault, memoryBlock: alignedData, blockLength: data.count, blockAllocator: nil, customBlockSource: nil, offsetToData: 0, dataLength: data.count, flags: 0, blockBufferOut: &blockBuffer ) guard blockStatus == kCMBlockBufferNoErr, let validBlockBuffer = blockBuffer else { alignedData.deallocate() throw NSError() } var sampleBuffer: CMSampleBuffer? var timing = [calculateTiming(for: segment)] var sampleSizes = [data.count] let sampleStatus = CMSampleBufferCreate( allocator: kCFAllocatorDefault, dataBuffer: validBlockBuffer, dataReady: true, makeDataReadyCallback: nil, refcon: nil, formatDescription: formatDescription, sampleCount: 1, sampleTimingEntryCount: 1, sampleTimingArray: &timing, sampleSizeEntryCount: sampleSizes.count, sampleSizeArray: &sampleSizes, sampleBufferOut: &sampleBuffer ) guard sampleStatus == noErr else { alignedData.deallocate() throw NSError() } return sampleBuffer } private func decodeSampleBuffer(_ sampleBuffer: CMSampleBuffer) throws { guard let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer) else { throw NSError() } if decompressionSession == nil { try setupDecompressionSession(formatDescription: formatDescription) } guard let session = decompressionSession else { throw NSError() } let flags: VTDecodeFrameFlags = [._EnableAsynchronousDecompression, ._EnableTemporalProcessing] var flagOut = VTDecodeInfoFlags() let status = VTDecompressionSessionDecodeFrame( session, sampleBuffer: sampleBuffer, flags: flags, frameRefcon: nil, infoFlagsOut: nil) if status != noErr { throw NSError() } } private func setupDecompressionSession(formatDescription: CMFormatDescription) throws { self.formatDescription = formatDescription if let session = decompressionSession { VTDecompressionSessionInvalidate(session) self.decompressionSession = nil } var decompressionSession: VTDecompressionSession? var callback = VTDecompressionOutputCallbackRecord( decompressionOutputCallback: decompressionOutputCallback, decompressionOutputRefCon: Unmanaged.passUnretained(self).toOpaque()) let status = VTDecompressionSessionCreate( allocator: kCFAllocatorDefault, formatDescription: formatDescription, decoderSpecification: nil, imageBufferAttributes: nil, outputCallback: &callback, decompressionSessionOut: &decompressionSession ) if status != noErr { throw NSError() } self.decompressionSession = decompressionSession } let decompressionOutputCallback: VTDecompressionOutputCallback = { ( decompressionOutputRefCon, sourceFrameRefCon, status, infoFlags, imageBuffer, presentationTimeStamp, presentationDuration ) in guard status == noErr else { print("Callback: \(status)") return } if let imageBuffer = imageBuffer { } }

Hi everyone, I'm developing a customization tool in which our customer can upload a mp3 or mp4 file that will be scannable through our AR application. On desktop and Android, this is working perfectly. For some reason however, on iPhone we're unable to load most of the video files. I've checked the clips, and they are .mov/h.264 files which are supported by iPhone. We're currently not sure how we can fix this issue to allow customers that own an iPhone to upload clips to our website. Any tips in the right direction are more than welcome. thanks in advance!

we are using angular and Html5 to develop our application, in our application we play videos that are placed on s3. Video when played on desktop borwser are adequatley audible but when played on iPad their volume is too low to be audible. I have tried video.volume =1 but it does not work for iPad because this property is only readable for ios devices. I have tried using javascript audioContext. It worked for my local machine. But when code is deployed on some hosted environments, it just does not work. Did anyone face the same issue? Any help regarding it will be appreciated.

We have developed a simple video player Swift application for macOS, which uses the AVFoundation Framework. A special feature of this app is the ability to play the video backward with speeds like -0.25x, -0.5x, and -1.0x. MP4 video file is played directly from the local file system, video codec is h.264, and audio AAC. Video files are huge, like 10 GB, and a length of 3 hours. Playing video in reverse direction works well on a Macbook Air with M1 or M2 chip. When we run the same app with the same video on a Macbook Air with M3 chip the reverse playback is much worse. Playback might stutter badly, especially in the latter part of the video. This same behavior also happens in Apple's Quicktime video player when playing in the reverse direction with -1x speed. What's even more strange is that at one point of a time, the video playback is totally smooth, but again, after a while, the playback is stuttering. For example, this morning reverse playback worked 100 % smoothly, then I rebooted the Mac and tried again: the result was stuttering. After this the Mac stayed idle for several hours and I tried to reverse play video again: smooth performance! My conclusion: M3 playback works fine if the stars in the sky are aligned correctly. :-) So it's not only our app, but also Quicktime player is having exactly the same behavior. And only with the M3 chip. The same symptom appears with another similar M3 Mac, so it can't be a single fault. At the same time, open-source video player iina can reverse play the video well on the same Mac. All Macs have otherwise identical configuration: 16 GB RAM and macOS 15.1.1. Have you experienced the same problem? Any chance to solve this problem? I really hope that the M4 chip Mac is behaving better here.

i use navigator.mediaDevices.getUserMedia to wake up camera, when i use constraint with '{video:{facingMode: {exact: 'user'}}}'，occur a error"invalid constraint"

My app is not a VOIP application. I use devices that support character centering, such as iPad 10 or iPad 13.18. The system is iOS 18.0, 18.1, or 18.1.1. When entering live classes, the "Character Centering" button does not appear in the control center, as shown in the following picture. However, if Voice over IP is selected for Background Modes in the project and the app is run again, it will not be reproduced, even if it is uninstalled or reinstalled. Could you please help me investigate the reason? thank you!

我的app不是VOIP应用，使用iPad10或者iPad13.18等支持人物居中的设备，系统是iOS18.0，18.1或者18.1.1，进入直播课中，控制中心不显示"人物居中"按钮，必现的，如下图。但是项目中Background Modes勾选Voice over IP，再次运行app，就不会再复现，即便是卸载重装也不会再复现。麻烦帮忙看看什么原因？谢谢

I don’t know what you felt was wrong with video scrubbing that you needed to **** it up this badly. I can’t scrub within the video, only within several seconds of the pause or worse it restarts the whole damn video. used to be an Easy and enjoyable process to harvest photos from a video and you’ve turned it into the most frustrating part of operating my phone. release me a patch to optionally enable the old scrubbing behavior.

We are processing videos with Core Image filters in our apps, using an AVMutableVideoComposition (for playback/preview and export). For older devices, we want to limit the resolution at which the video frames are processed for performance and memory reasons. Ideally, we would tell AVFoundation to give us video frames with a defined maximum size into our composition. We thought setting the renderSize property of the composition to the desired size would do that. However, this only changes the size of output frames, not the size of the source frames that come into the composition's handler block. For example: let composition = AVMutableVideoComposition(asset: asset, applyingCIFiltersWithHandler: { request in let input = request.sourceImage // <- this still has the video's original size // ... }) composition.renderSize = CGSize(width: 1280, heigth: 720) // for example So if the user selects a 4K video, our filter chain gets 4K input frames. Sure, we can scale them down inside our pipeline, but this costs resources and especially a lot of memory. It would be way better if AVFoundation could decode the video frames in the desired size already before passing it into the composition handler. Is there a way to tell AVFoundation to load smaller video frames?

I would like to take YCbCr CVPixelBuffers from AVCaptureVideoDataOutput, apply some processing in RGB space, render to an MTKView, and pass to AVAssetWriter for recording. Right now, I'm doing this all manually – deswing the incoming data if necessary, choose the right matrix to convert to RGB, apply processing, etc. I also have to convert back to YCbCr before feeding the frames to AVAssetWriter because encoding performs much better if I do. Is there any efficient, built-in way to achieve the same? I can't use AVCaptureVideoPreviewLayer, since I need to do some further processing before display. I can't use AVCaptureVideoDataOutput's videoSettings to get automatic BGRA conversion because that would lose bit depth for 10 bit video formats (and isn't available on all formats anyway). I see these Accelerate functions, but they seemingly don't use the GPU, nor do they support all the formats and bit depths I'd need. I found reference to some undocumented MTLPixelFormats that seem to do exactly what I want, but I don't want to rely on something like this unless it's explicitly endorsed. This would also incur an RGB/YCbCr conversion on every texture read and write, right? Is there anything I'm missing here?

I have an webview that loads videos in it, we would like to be able to fullscreen our videos, so we use the fullscreen preference in the documentation however when it is set to true, upon fullscreening a video then pausing it, the entire video player will disappear. You can exit fullscreen and attempt to fullscreen the video player once again, however upon doing this the entire app view will now disappear and you'll see your desktop background (or whatever is currently behind your app). This behavior seems consistent across multiple websites with the current app. I have setup a sample project you can test here The Main error that seems to trigger to the console is this. I have not been able to find a solution to, maybe I am simply missing something here. I am on Sequoia 15.2 for Mac. Attempting to update all DD element frames, but the bounds or contentsRect are invalid. Bounds: X: 0.00 Y: 0.00, W: 0.00 H: 0.00, contentsRect: X: 0.00 Y: 0.00, W: 1.00 H: 1.00 , skipping

We have had the same video player in our app for at least 5 years with few issues but the iOS 18 updated has now resulted in video playback for our users who have downloaded the video for offline viewing is now played at 2x speed.

The strange_behaviour.mp4 video attached shows how when running a list of statements to open (startCamera) and close (closeCamera) the camera against a MacBook Pro 2019 using the FaceTime camera, these return their value almost immediately, when in reality the camera is still opening and closing. We believe that there might be a queue for statements to run against the camera and it finishes the awaits when all the statements are inserted in the queue instead of when they are actually solved. We also attached the expected_behaviour.mp4 video where we replicate the same flow but using an external camera instead of the FaceTime camera. In this video, the promises take a bit longer to return but they do once the camera has already been opened and closed the requested amount of times. The project used in the videos is attached as project.tar.xz. We would like to know if the behaviour in strange_behaviour.mp4 is replicable on your side and if there is a way to access the cameras to make it behave like when using an external camera (expected_behaviour.mp4). Attachments: https://drive.google.com/drive/folders/1cOeFb5GMbh4mPOeZiZyyevk3N778Kn1M?usp=sharing

I'm experiencing a persistent issue with transparent WebM videos rendered via WKWebView in an iOS Capacitor app. The videos play normal, however, they display a black background frame, which does not occur in the web version of the app. I've tried: Playing with the css setting, Enabling experimental WKWebView features, Adjusting meta tags for inline video playback and hardware acceleration. That my code: showThumbs={false} showStatus={false} showIndicators={true} showArrows={false} infiniteLoop={true} autoPlay={true} interval={5000} // Change slide every 5 seconds onChange={(index) => { if (playerRefs.current[index]) { playerRefs.current[index]?.seekTo(0); playerRefs.current[index]?.getInternalPlayer()?.play(); } }} > {videos.map((video, index) => ( <div key={index} className="video-slide"> <ReactPlayer ref={(player) => (playerRefs.current[index] = player)} url={video.src} playing={isLoaded[index]} // Play only when video is loaded loop muted width="100%" onReady={() => handleVideoReady(index)} // Set loaded state when video is ready style={{ backgroundColor: 'transparent' }} config={{ file: { attributes: { playsInline: true, }, }, }} /> <p className="description">{video.description}</p> </div> ))} </Carousel> Working with React, capacitor. The videos work perfect when I test it on the web app, the problem occurs just on my ios app

在webview全屏打开Video视频前后获取设备的宽高结果不同 [UIScreen mainScreen].bounds对应的设备逻辑分辨率发生变化，导致根据分辨率显示的页面显示错误