使用框架：AVFoundation
实现步骤：
1、设置FPS：采集的视频有要求的话，这一步是必须的；FPS默认30。这里采用最大FPS：240。
captureSession.beginConfiguration()
captureSession.sessionPreset = .hd1280x720
var bestFormat: AVCaptureDevice.Format?
var maxRate: AVFrameRateRange?
for format in device.formats {
for range in format.videoSupportedFrameRateRanges {
if maxRate?.maxFrameRate ?? 0 < range.maxFrameRate {
maxRate = range
bestFormat = format
}
}
}
if let bestFormat = bestFormat, let maxRange = maxRate {
do {
try device.lockForConfiguration()
device.activeFormat = bestFormat
let duration = maxRange.minFrameDuration
device.activeVideoMaxFrameDuration = duration
device.activeVideoMinFrameDuration = duration
device.unlockForConfiguration()
} catch {
print(error.localizedDescription)
}
}
captureSession.commitConfiguration()
注意：
修改activeFormat需要使用方法device.lockForConfiguration()，否则会crash；
不同FPS，支持的分辨率也不同，240的FPS只有分辨率1280x720支持：sessionPreset = .hd1280x720 ；
修改device参数，需要更新session，否则修改无效：captureSession.commitConfiguration()。
2、视频录制：使用系统类AVCaptureMovieFileOutput，当然，也可以自己写writer。
// 添加output，如果自己写writer，或者实时处理buffer，需要用AVCaptureVideoDataOutput
let movieFileOutput = AVCaptureMovieFileOutput()
if captureSession.canAddOutput(movieFileOutput) {
captureSession.addOutput(movieFileOutput)
if let connection = movieFileOutput.connection(with: .video) {
captureSession.beginConfiguration()
if connection.isVideoStabilizationSupported {
connection.preferredVideoStabilizationMode = .auto
}
if connection.isVideoOrientationSupported {
connection.videoOrientation = .landscapeRight
}
captureSession.commitConfiguration()
}
}
// 代理
func fileOutput(_ output: AVCaptureFileOutput, didStartRecordingTo fileURL: URL, from connections: [AVCaptureConnection]) {}
func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {}
3、视频压缩：将FPS压缩8倍（240->30）。
guard let track = videoAsset.tracks(withMediaType: .video).first else {
errorCallback?("读取视频信息失败")
return
}
let mixComposition = AVMutableComposition()
let duration = videoAsset.duration
guard
let composTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid),
let _ = try? composTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: duration), of: track, at: .zero)
else {
errorCallback?("读取视频信息失败")
return
}
let factor = 8
composTrack.scaleTimeRange(CMTimeRangeMake(start: .zero, duration: duration), toDuration: CMTimeMake(value: duration.value * Int64(factor), timescale: duration.timescale))
guard let export = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPreset1280x720) else {
errorCallback?("读取视频信息失败")
return
}
let outURL = URL(fileURLWithPath: NSTemporaryDirectory() + "temp_compose.mp4")
try? FileManager.default.removeItem(at: outURL)
export.outputURL = outURL
export.outputFileType = AVFileType.mp4
export.shouldOptimizeForNetworkUse = true
weak var weakSelf = self
export.exportAsynchronously {
DispatchQueue.main.async {
if export.status == .completed {
//outURL
}
}
}
注意：export回调中，进度是没有的，需要自行获取
4、获取压缩进度：
let timer = Timer(timeInterval: 0.1, repeats: true) { (_) in
weakSelf?.trackCallback?(export.progress)
}
RunLoop.main.add(timer, forMode: .common)
总结：
实现很简单，都是很成熟的API，github上也有几个现成的开源项目，想学习的可以手动实现一下。
参考地址：
1: How to do Slow Motion video in IOS；
2: Handling Frame Drops with AVCaptureVideoDataOutput。