如何解决你如何只将某些 CMSampleBuffer 帧写入 AVFoundation 中的新电影文件?
我想对用户导入的视频执行姿势分析,自动生成 AVFoundation
视频输出,其中只有带有 a detected pose 的帧是结果的一部分。在 Building a Feature-Rich App for Sports Analysis 示例代码中,通过实现 func cameraViewController(_ controller: CameraViewController,didReceiveBuffer buffer: CMSampleBuffer,orientation: CGImagePropertyOrientation)
委托回调进行分析,例如 GameViewController.swift
的第 326 行。
我遇到的问题是使用此分析来仅保留检测到姿势的特定帧。假设我已经分析了所有 CMSampleBuffer
帧并分类了哪些具有我想要的姿势。我如何只为新视频输出使用那些特定的帧?
Apple 文档档案中的“AVFoundation 编程指南”链接已损坏,因此很难找到概念性解释。首选 Swift 中的答案,但 Objective-C 仍然会有所帮助。
解决方法
如果你想记录 CMSampleBuffer,你可以使用这个代码:
import Foundation
import AVFoundation
class MovieRecorder {
private var assetWriter: AVAssetWriter?
private var assetWriterVideoInput: AVAssetWriterInput?
private var assetWriterAudioInput: AVAssetWriterInput?
private var videoTransform: CGAffineTransform
private var videoSettings: [String: Any]
private var audioSettings: [String: Any]
private(set) var isRecording = false
init(audioSettings: [String: Any],videoSettings: [String: Any],videoTransform: CGAffineTransform) {
self.audioSettings = audioSettings
self.videoSettings = videoSettings
self.videoTransform = videoTransform
}
func startRecording() {
// Create an asset writer that records to a temporary file
let outputFileName = NSUUID().uuidString
let outputFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(outputFileName).appendingPathExtension("MOV")
guard let assetWriter = try? AVAssetWriter(url: outputFileURL,fileType: .mov) else {
return
}
// Add an audio input
let assetWriterAudioInput = AVAssetWriterInput(mediaType: .audio,outputSettings: audioSettings)
assetWriterAudioInput.expectsMediaDataInRealTime = true
assetWriter.add(assetWriterAudioInput)
// Add a video input
let assetWriterVideoInput = AVAssetWriterInput(mediaType: .video,outputSettings: videoSettings)
assetWriterVideoInput.expectsMediaDataInRealTime = true
assetWriterVideoInput.transform = videoTransform
assetWriter.add(assetWriterVideoInput)
self.assetWriter = assetWriter
self.assetWriterAudioInput = assetWriterAudioInput
self.assetWriterVideoInput = assetWriterVideoInput
isRecording = true
}
func stopRecording(completion: @escaping (URL) -> Void) {
guard let assetWriter = assetWriter else {
return
}
self.isRecording = false
self.assetWriter = nil
assetWriter.finishWriting {
completion(assetWriter.outputURL)
}
}
func recordVideo(sampleBuffer: CMSampleBuffer) {
guard isRecording,let assetWriter = assetWriter else {
return
}
if assetWriter.status == .unknown {
assetWriter.startWriting()
assetWriter.startSession(atSourceTime: CMSampleBufferGetPresentationTimeStamp(sampleBuffer))
} else if assetWriter.status == .writing {
if let input = assetWriterVideoInput,input.isReadyForMoreMediaData {
input.append(sampleBuffer)
}
}
}
func recordAudio(sampleBuffer: CMSampleBuffer) {
guard isRecording,let assetWriter = assetWriter,assetWriter.status == .writing,let input = assetWriterAudioInput,input.isReadyForMoreMediaData else {
return
}
input.append(sampleBuffer)
}
}
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