对于如何使用AVAssetWriter快速整理视频？感兴趣的读者，本文将提供您所需要的所有信息，我们将详细讲解avistreamwrite，并且为您提供关于asp.net-mvc-2–在MVC2中使用

对于如何使用AVAssetWriter快速整理视频？感兴趣的读者，本文将提供您所需要的所有信息，我们将详细讲解avistreamwrite，并且为您提供关于asp.net-mvc-2 – 在MVC 2中使用自定义TextWriter时,“BinaryWrite异常”OutputStream不可用ASP.NET 4、AVAssetWriter AVVideoExpectedSourceFrameRateKey（帧频）已忽略、AVAssetWriter在iOS 14上的压缩过程中创建工件、AVAssetWriter视频数据编码的宝贵知识。

• 如何使用AVAssetWriter快速整理视频？（avistreamwrite）
• asp.net-mvc-2 – 在MVC 2中使用自定义TextWriter时,“BinaryWrite异常”OutputStream不可用ASP.NET 4
• AVAssetWriter AVVideoExpectedSourceFrameRateKey（帧频）已忽略
• AVAssetWriter在iOS 14上的压缩过程中创建工件
• AVAssetWriter视频数据编码

如何使用AVAssetWriter快速整理视频？（avistreamwrite）

我目前正在制作一个小型应用程序，该程序可以使Mac上的网络摄像头延时播放，将捕获的帧保存为png，并且正在考虑将捕获的帧导出为单个视频。

我使用CGImage处理原始图像，并将它们设置在数组中，但是我不确定从那里开始。根据我自己的研究，我不得不以某种方式使用AVAssetWriter和AVAssetWriterInput。

我在这里浏览了一下，阅读了苹果文档并搜索了谷歌。但是所有指南等都在obj-c中，而不是快捷的，这使得它真的很难理解（因为我没有Obj-C的经验）。

任何帮助将不胜感激。

非常感谢，卢克。

答案1

我在Swift中解决了同样的问题。从UIImage数组开始，尝试一下（有点长：-），但是可以）：

var choosenPhotos: [UIImage] = [] *** your array of UIImages ***var outputSize = CGSizeMake(1280, 720)func build(outputSize outputSize: CGSize) {    let fileManager = NSFileManager.defaultManager()    let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)    guard let documentDirectory: NSURL = urls.first else {        fatalError("documentDir Error")    }    let videoOutputURL = documentDirectory.URLByAppendingPathComponent("OutputVideo.mp4")    if NSFileManager.defaultManager().fileExistsAtPath(videoOutputURL.path!) {        do {            try NSFileManager.defaultManager().removeItemAtPath(videoOutputURL.path!)        } catch {            fatalError("Unable to delete file: \(error) : \(__FUNCTION__).")        }    }    guard let videoWriter = try? AVAssetWriter(URL: videoOutputURL, fileType: AVFileTypeMPEG4) else {        fatalError("AVAssetWriter error")    }    let outputSettings = [AVVideoCodecKey : AVVideoCodecH264, AVVideoWidthKey : NSNumber(float: Float(outputSize.width)), AVVideoHeightKey : NSNumber(float: Float(outputSize.height))]    guard videoWriter.canApplyOutputSettings(outputSettings, forMediaType: AVMediaTypeVideo) else {        fatalError("Negative : Can''t apply the Output settings...")    }    let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: outputSettings)    let sourcePixelBufferAttributesDictionary = [kCVPixelBufferPixelFormatTypeKey as String : NSNumber(unsignedInt: kCVPixelFormatType_32ARGB), kCVPixelBufferWidthKey as String: NSNumber(float: Float(outputSize.width)), kCVPixelBufferHeightKey as String: NSNumber(float: Float(outputSize.height))]    let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput, sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)    if videoWriter.canAddInput(videoWriterInput) {        videoWriter.addInput(videoWriterInput)    }    if videoWriter.startWriting() {        videoWriter.startSessionAtSourceTime(kCMTimeZero)        assert(pixelBufferAdaptor.pixelBufferPool != nil)        let media_queue = dispatch_queue_create("mediaInputQueue", nil)        videoWriterInput.requestMediaDataWhenReadyOnQueue(media_queue, usingBlock: { () -> Void in            let fps: Int32 = 1            let frameDuration = CMTimeMake(1, fps)            var frameCount: Int64 = 0            var appendSucceeded = true            while (!self.choosenPhotos.isEmpty) {                if (videoWriterInput.readyForMoreMediaData) {                    let nextPhoto = self.choosenPhotos.removeAtIndex(0)                    let lastFrameTime = CMTimeMake(frameCount, fps)                    let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)                    var pixelBuffer: CVPixelBuffer? = nil                    let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pixelBufferAdaptor.pixelBufferPool!, &pixelBuffer)                    if let pixelBuffer = pixelBuffer where status == 0 {                        let managedPixelBuffer = pixelBuffer                        CVPixelBufferLockBaseAddress(managedPixelBuffer, 0)                        let data = CVPixelBufferGetBaseAddress(managedPixelBuffer)                        let rgbColorSpace = CGColorSpaceCreateDeviceRGB()                        let context = CGBitmapContextCreate(data, Int(self.outputSize.width), Int(self.outputSize.height), 8, CVPixelBufferGetBytesPerRow(managedPixelBuffer), rgbColorSpace, CGImageAlphaInfo.PremultipliedFirst.rawValue)                        CGContextClearRect(context, CGRectMake(0, 0, CGFloat(self.outputSize.width), CGFloat(self.outputSize.height)))                        let horizontalRatio = CGFloat(self.outputSize.width) / nextPhoto.size.width                        let verticalRatio = CGFloat(self.outputSize.height) / nextPhoto.size.height                        //aspectRatio = max(horizontalRatio, verticalRatio) // ScaleAspectFill                        let aspectRatio = min(horizontalRatio, verticalRatio) // ScaleAspectFit                        let newSize:CGSize = CGSizeMake(nextPhoto.size.width * aspectRatio, nextPhoto.size.height * aspectRatio)                        let x = newSize.width < self.outputSize.width ? (self.outputSize.width - newSize.width) / 2 : 0                        let y = newSize.height < self.outputSize.height ? (self.outputSize.height - newSize.height) / 2 : 0                        CGContextDrawImage(context, CGRectMake(x, y, newSize.width, newSize.height), nextPhoto.CGImage)                        CVPixelBufferUnlockBaseAddress(managedPixelBuffer, 0)                        appendSucceeded = pixelBufferAdaptor.appendPixelBuffer(pixelBuffer, withPresentationTime: presentationTime)                    } else {                        print("Failed to allocate pixel buffer")                        appendSucceeded = false                    }                }                if !appendSucceeded {                    break                }                frameCount++            }            videoWriterInput.markAsFinished()            videoWriter.finishWritingWithCompletionHandler { () -> Void in                print("FINISHED!!!!!")            }        })    }}

asp.net-mvc-2 – 在MVC 2中使用自定义TextWriter时,“BinaryWrite异常”OutputStream不可用ASP.NET 4

<%@ Page Title="" Language="C#" Inherits="System.Web.Mvc.ViewPage" %>
<%@ Import Namespace="System.IO" %>
<script runat="server">
protected void  Page_Load(object sender,EventArgs e)
{
    if (ViewData["Error"] == null)
    {

        Response.Buffer = true;
        Response.Clear();
        Response.ContentType = ViewData["DocType"] as string;
        response.addheader("content-disposition",ViewData["disposition"] as string);
        Response.CacheControl = "No-cache";
        MemoryStream stream = ViewData["DocAsstream"] as MemoryStream;
        Response.BinaryWrite(stream.ToArray());
        Response.Flush();
        Response.Close();
    }
}   
</script>


</script>

AVAssetWriter AVVideoExpectedSourceFrameRateKey（帧频）已忽略

我和我的团队正在尝试通过更改视频帧频来对视频文件进行重新编码，以使其更具“格调”感。我们将以下属性用于AVAssetWriterInput：

let videoSettings:[String:Any] = [            AVVideoCodecKey: AVVideoCodecH264,            AVVideoHeightKey: videoTrack.naturalSize.height,            AVVideoWidthKey: videoTrack.naturalSize.width,            AVVideoCompressionPropertiesKey: [AVVideoExpectedSourceFrameRateKey: NSNumber(value: 12)]                                                 ]

但是输出视频仍以正常帧频播放（使用播放AVPlayer）。

降低视频帧速率的正确方法是什么？ （例如12）。

朝着正确方向的任何帮助都将受到高度重视。 我们卡住了。此致Roi

答案1

您可以控制附加到每个样品的时间AVAssetWriterInput直接CMSampleBufferCreateCopyWithNewTiming。

您需要在CMSampleTimingInfo提供的时间中调整时间。使用CMSampleBufferGetOutputSampleTimingInfoArray和检索当前的时间信息，然后遍历每个样本的持续时间，并计算正确的持续时间以每秒获取12帧，并调整演示和解码时间戳以匹配此新的持续时间。然后，您制作副本并将其提供给作者的输入。

假设您有existingSampleBuffer：

CMSampleBufferRef sampleBufferToWrite = NULL;CMSampleTimingInfo sampleTimingInfo = {0};CMSampleBufferGetSampleTimingInfo(existingSampleBuffer, 0, &sampleTimingInfo);// modify duration & presentationTimeStampsampleTimingInfo.duration = CMTimeMake(1, 12) // or whatever frame rate you desiresampleTimingInfo.presentationTimeStamp = CMTimeAdd(previousPresentationTimeStamp, sampleTimingInfo.duration);previousPresentationTimeStamp = sampleTimingInfo.presentationTimeStamp; // should be initialised before passing here the first timeOSStatus status = CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault, existingSampleBuffer, 1, &sampleTimingInfo, &sampleBufferToWrite);if (status == noErr) {    // you can write sampleBufferToWrite}

我在这段代码中做一些假设：

• SampleBuffer仅包含一个样本
• SampleBuffer包含未压缩的视频（否则，您还需要处理decodeTimeStamp）

AVAssetWriter在iOS 14上的压缩过程中创建工件

AVAssetWriter

 NSError * error;
_mAssetWriter = [[AVAssetWriter alloc] initWithURL:videoUrl fileType:AVFileTypeAppleM4V error:&error];