我正在尝试使用AVCaptureSession在内存中捕获相机视频，以便稍后我可以将视频数据写入电影文件。虽然我已经能够成功启动捕获会话，但我无法使用AVAssetWriter将已捕获的CMSampleBuffers写入压缩的电影文件。
使用AVAssetWriterInput的append方法追加样本缓冲区失败，当我检查AVAssetWriter的错误属性时，我得到以下内容：
错误域= AVFoundationErrorDomain代码= -11800＆＃34;操作无法完成＆＃34; UserInfo = {NSUnderlyingError = 0x17005d070 {Error Domain = NSOSStatusErrorDomain Code = -12780＆＃34;（null）＆＃34;}，NSLocalizedFailureReason =发生未知错误（-12780），NSLocalizedDescription =操作无法完成}
据我所知-11800表示AVErrorUnknown，但是我无法找到有关-12780错误代码的信息，据我所知，该错误代码没有记录。下面我已经粘贴了我设置的示例项目中的主要文件来演示问题。
非常感谢任何指导。谢谢！
ViewController.swift
import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
private let recordingClipQueue = DispatchQueue(label: "com.example.recordingClipQueue")
private let videoDataOutputQueue = DispatchQueue(label: "com.example.videoDataOutputQueue")
private let session = AVCaptureSession()
private var backfillSampleBufferList = [CMSampleBuffer]()
override func viewDidLoad() {
super.viewDidLoad()
session.sessionPreset = AVCaptureSessionPreset640x480
let videoDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo);
let videoDeviceInput: AVCaptureDeviceInput;
do {
videoDeviceInput = try AVCaptureDeviceInput(device: videoDevice)
} catch {
print("Error creating device input from video device: \(error).")
return
}
guard session.canAddInput(videoDeviceInput) else {
print("Could not add video device input to capture session.")
return
}
session.addInput(videoDeviceInput)
let videoDataOutput = AVCaptureVideoDataOutput()
videoDataOutput.videoSettings = [ kCVPixelBufferPixelFormatTypeKey as NSString : Int(kCMPixelFormat_32BGRA) ]
videoDataOutput.alwaysDiscardsLateVideoFrames = true
videoDataOutput.setSampleBufferDelegate(self, queue: videoDataOutputQueue)
guard session.canAddOutput(videoDataOutput) else {
print("Could not add video data output to capture session.")
return
}
session.addOutput(videoDataOutput)
videoDataOutput.connection(withMediaType: AVMediaTypeVideo).isEnabled = true
session.startRunning()
}
private func backfillSizeInSeconds() -> Double {
if backfillSampleBufferList.count < 1 {
return 0.0
}
let earliestSampleBuffer = backfillSampleBufferList.first!
let latestSampleBuffer = backfillSampleBufferList.last!
let earliestSampleBufferPTS = CMSampleBufferGetOutputPresentationTimeStamp(earliestSampleBuffer).value
let latestSampleBufferPTS = CMSampleBufferGetOutputPresentationTimeStamp(latestSampleBuffer).value
let timescale = CMSampleBufferGetOutputPresentationTimeStamp(latestSampleBuffer).timescale
return Double(latestSampleBufferPTS - earliestSampleBufferPTS) / Double(timescale)
}
private func createClipFromBackfill() {
guard backfillSampleBufferList.count > 0 else {
print("createClipFromBackfill() called before any samples were recorded.")
return
}
let clipURL = URL(fileURLWithPath:
NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] +
"/recorded_clip.mp4")
if FileManager.default.fileExists(atPath: clipURL.path) {
do {
try FileManager.default.removeItem(atPath: clipURL.path)
} catch {
print("Could not delete existing clip file: \(error).")
}
}
var _videoFileWriter: AVAssetWriter?
do {
_videoFileWriter = try AVAssetWriter(url: clipURL, fileType: AVFileTypeQuickTimeMovie)
} catch {
print("Could not create video file writer: \(error).")
return
}
guard let videoFileWriter = _videoFileWriter else {
print("Video writer was nil.")
return
}
let settingsAssistant = AVOutputSettingsAssistant(preset: AVOutputSettingsPreset640x480)!
guard videoFileWriter.canApply(outputSettings: settingsAssistant.videoSettings, forMediaType: AVMediaTypeVideo) else {
print("Video file writer could not apply video output settings.")
return
}
let earliestRecordedSampleBuffer = backfillSampleBufferList.first!
let _formatDescription = CMSampleBufferGetFormatDescription(earliestRecordedSampleBuffer)
guard let formatDescription = _formatDescription else {
print("Earliest recording pixel buffer format description was nil.")
return
}
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo,
outputSettings: settingsAssistant.videoSettings,
sourceFormatHint: formatDescription)
guard videoFileWriter.canAdd(videoWriterInput) else {
print("Could not add video writer input to video file writer.")
return
}
videoFileWriter.add(videoWriterInput)
guard videoFileWriter.startWriting() else {
print("Video file writer not ready to write file.")
return
}
videoFileWriter.startSession(atSourceTime: CMSampleBufferGetOutputPresentationTimeStamp(earliestRecordedSampleBuffer))
videoWriterInput.requestMediaDataWhenReady(on: recordingClipQueue) {
while videoWriterInput.isReadyForMoreMediaData {
if self.backfillSampleBufferList.count > 0 {
let sampleBufferToAppend = self.backfillSampleBufferList.first!.deepCopy()
let appendSampleBufferSucceeded = videoWriterInput.append(sampleBufferToAppend)
if !appendSampleBufferSucceeded {
print("Failed to append sample buffer to asset writer input: \(videoFileWriter.error!)")
print("Video file writer status: \(videoFileWriter.status.rawValue)")
}
self.backfillSampleBufferList.remove(at: 0)
} else {
videoWriterInput.markAsFinished()
videoFileWriter.finishWriting {
print("Saved clip to \(clipURL)")
}
break
}
}
}
}
// MARK: AVCaptureVideoDataOutputSampleBufferDelegate
func captureOutput(_ captureOutput: AVCaptureOutput!,
didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
from connection: AVCaptureConnection!) {
guard let buffer = sampleBuffer else {
print("Captured sample buffer was nil.")
return
}
let sampleBufferCopy = buffer.deepCopy()
backfillSampleBufferList.append(sampleBufferCopy)
if backfillSizeInSeconds() > 3.0 {
session.stopRunning()
createClipFromBackfill()
}
}
func captureOutput(_ captureOutput: AVCaptureOutput!,
didDrop sampleBuffer: CMSampleBuffer!,
from connection: AVCaptureConnection!) {
print("Sample buffer dropped.")
}
}
CVPixelBuffer + Copy.swift：
import CoreVideo
extension CVPixelBuffer {
func deepCopy() -> CVPixelBuffer {
precondition(CFGetTypeID(self) == CVPixelBufferGetTypeID(), "deepCopy() cannot copy a non-CVPixelBuffer")
var _copy : CVPixelBuffer?
CVPixelBufferCreate(
nil,
CVPixelBufferGetWidth(self),
CVPixelBufferGetHeight(self),
CVPixelBufferGetPixelFormatType(self),
CVBufferGetAttachments(self, CVAttachmentMode.shouldPropagate),
&_copy)
guard let copy = _copy else {
print("Pixel buffer copy was nil.")
fatalError()
}
CVBufferPropagateAttachments(self, copy)
CVPixelBufferLockBaseAddress(self, CVPixelBufferLockFlags.readOnly)
CVPixelBufferLockBaseAddress(copy, CVPixelBufferLockFlags(rawValue: 0))
let sourceBaseAddress = CVPixelBufferGetBaseAddress(self)
let copyBaseAddress = CVPixelBufferGetBaseAddress(copy)
memcpy(copyBaseAddress, sourceBaseAddress, CVPixelBufferGetHeight(self) * CVPixelBufferGetBytesPerRow(self))
CVPixelBufferUnlockBaseAddress(copy, CVPixelBufferLockFlags(rawValue: 0))
CVPixelBufferUnlockBaseAddress(self, CVPixelBufferLockFlags.readOnly)
return copy
}
}
CMSampleBuffer + Copy.swift：
import CoreMedia
extension CMSampleBuffer {
func deepCopy() -> CMSampleBuffer {
let _pixelBuffer = CMSampleBufferGetImageBuffer(self)
guard let pixelBuffer = _pixelBuffer else {
print("Pixel buffer to copy was nil.")
fatalError()
}
let pixelBufferCopy = pixelBuffer.deepCopy()
let _formatDescription = CMSampleBufferGetFormatDescription(self)
guard let formatDescription = _formatDescription else {
print("Format description to copy was nil.")
fatalError()
}
var timingInfo = kCMTimingInfoInvalid
let getTimingInfoResult = CMSampleBufferGetSampleTimingInfo(self, 0, &timingInfo)
guard getTimingInfoResult == noErr else {
print("Could not get timing info to copy: \(getTimingInfoResult).")
fatalError()
}
timingInfo.presentationTimeStamp = CMSampleBufferGetOutputPresentationTimeStamp(self)
var _copy : CMSampleBuffer?
let createCopyResult = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault,
pixelBufferCopy,
true,
nil,
nil,
formatDescription,
&timingInfo,
&_copy);
guard createCopyResult == noErr else {
print("Error creating copy of sample buffer: \(createCopyResult).")
fatalError()
}
guard let copy = _copy else {
print("Copied sample buffer was nil.")
fatalError()
}
return copy
}
}
答案 0 :(得分：2)
经过更多的研究和实验，看来使用AVAssetWriterInputPixelBufferAdaptor将我存储的CMSampleBuffers的CVPixelBuffers附加到AVAssetWriterInput工作而不会产生错误。
以下是ViewController.swift实现的修改版本，该实现使用AVAssetWriterInputPixelBufferAdaptor附加像素缓冲区。
ViewController.swift
import UIKit
import AVFoundation
import Photos
class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
private let recordingClipQueue = DispatchQueue(label: "com.example.recordingClipQueue")
private let videoDataOutputQueue = DispatchQueue(label: "com.example.videoDataOutputQueue")
private let session = AVCaptureSession()
private var backfillSampleBufferList = [CMSampleBuffer]()
override func viewDidLoad() {
super.viewDidLoad()
session.sessionPreset = AVCaptureSessionPreset640x480
let videoDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo);
let videoDeviceInput: AVCaptureDeviceInput;
do {
videoDeviceInput = try AVCaptureDeviceInput(device: videoDevice)
} catch {
print("Error creating device input from video device: \(error).")
return
}
guard session.canAddInput(videoDeviceInput) else {
print("Could not add video device input to capture session.")
return
}
session.addInput(videoDeviceInput)
let videoDataOutput = AVCaptureVideoDataOutput()
videoDataOutput.videoSettings = [ kCVPixelBufferPixelFormatTypeKey as NSString : Int(kCMPixelFormat_32BGRA) ]
videoDataOutput.alwaysDiscardsLateVideoFrames = true
videoDataOutput.setSampleBufferDelegate(self, queue: videoDataOutputQueue)
guard session.canAddOutput(videoDataOutput) else {
print("Could not add video data output to capture session.")
return
}
session.addOutput(videoDataOutput)
videoDataOutput.connection(withMediaType: AVMediaTypeVideo).isEnabled = true
session.startRunning()
}
private func backfillSizeInSeconds() -> Double {
if backfillSampleBufferList.count < 1 {
return 0.0
}
let earliestSampleBuffer = backfillSampleBufferList.first!
let latestSampleBuffer = backfillSampleBufferList.last!
let earliestSampleBufferPTS = CMSampleBufferGetOutputPresentationTimeStamp(earliestSampleBuffer).value
let latestSampleBufferPTS = CMSampleBufferGetOutputPresentationTimeStamp(latestSampleBuffer).value
let timescale = CMSampleBufferGetOutputPresentationTimeStamp(latestSampleBuffer).timescale
return Double(latestSampleBufferPTS - earliestSampleBufferPTS) / Double(timescale)
}
private func createClipFromBackfill() {
guard backfillSampleBufferList.count > 0 else {
print("createClipFromBackfill() called before any samples were recorded.")
return
}
let clipURL = URL(fileURLWithPath:
NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] +
"/recorded_clip.mp4")
if FileManager.default.fileExists(atPath: clipURL.path) {
do {
try FileManager.default.removeItem(atPath: clipURL.path)
} catch {
print("Could not delete existing clip file: \(error).")
}
}
var _videoFileWriter: AVAssetWriter?
do {
_videoFileWriter = try AVAssetWriter(url: clipURL, fileType: AVFileTypeMPEG4)
} catch {
print("Could not create video file writer: \(error).")
return
}
guard let videoFileWriter = _videoFileWriter else {
print("Video writer was nil.")
return
}
let settingsAssistant = AVOutputSettingsAssistant(preset: AVOutputSettingsPreset640x480)!
guard videoFileWriter.canApply(outputSettings: settingsAssistant.videoSettings, forMediaType: AVMediaTypeVideo) else {
print("Video file writer could not apply video output settings.")
return
}
let earliestRecordedSampleBuffer = backfillSampleBufferList.first!
let _formatDescription = CMSampleBufferGetFormatDescription(earliestRecordedSampleBuffer)
guard let formatDescription = _formatDescription else {
print("Earliest recording pixel buffer format description was nil.")
return
}
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo,
outputSettings: settingsAssistant.videoSettings,
sourceFormatHint: formatDescription)
guard videoFileWriter.canAdd(videoWriterInput) else {
print("Could not add video writer input to video file writer.")
return
}
videoFileWriter.add(videoWriterInput)
let pixelAdapterBufferAttributes = [ kCVPixelBufferPixelFormatTypeKey as String : Int(kCMPixelFormat_32BGRA) ]
let pixelAdapter = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput,
sourcePixelBufferAttributes: pixelAdapterBufferAttributes)
guard videoFileWriter.startWriting() else {
print("Video file writer not ready to write file.")
return
}
videoFileWriter.startSession(atSourceTime: CMSampleBufferGetOutputPresentationTimeStamp(earliestRecordedSampleBuffer))
videoWriterInput.requestMediaDataWhenReady(on: recordingClipQueue) {
while videoWriterInput.isReadyForMoreMediaData {
if self.backfillSampleBufferList.count > 0 {
let sampleBufferToAppend = self.backfillSampleBufferList.first!.deepCopy()
let appendSampleBufferSucceeded = pixelAdapter.append(CMSampleBufferGetImageBuffer(sampleBufferToAppend)!,
withPresentationTime: CMSampleBufferGetOutputPresentationTimeStamp(sampleBufferToAppend))
if !appendSampleBufferSucceeded {
print("Failed to append sample buffer to asset writer input: \(videoFileWriter.error!)")
print("Video file writer status: \(videoFileWriter.status.rawValue)")
}
self.backfillSampleBufferList.remove(at: 0)
} else {
videoWriterInput.markAsFinished()
videoFileWriter.finishWriting {
print("Saving clip to \(clipURL)")
}
break
}
}
}
}
// MARK: AVCaptureVideoDataOutputSampleBufferDelegate
func captureOutput(_ captureOutput: AVCaptureOutput!,
didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
from connection: AVCaptureConnection!) {
guard let buffer = sampleBuffer else {
print("Captured sample buffer was nil.")
return
}
let sampleBufferCopy = buffer.deepCopy()
backfillSampleBufferList.append(sampleBufferCopy)
if backfillSizeInSeconds() > 3.0 {
session.stopRunning()
createClipFromBackfill()
}
}
func captureOutput(_ captureOutput: AVCaptureOutput!,
didDrop sampleBuffer: CMSampleBuffer!,
from connection: AVCaptureConnection!) {
print("Sample buffer dropped.")
}
}
答案 1 :(得分：2)
我在尝试合成视频时遇到了这个问题。我终于发现-[AVAssetWriterInput appendSampleBuffer:]仅适用于设备（无论如何，从iOS 11.2.6开始），如果底层像素缓冲区由IOSurface支持。
如果您修改了CVPixelBuffer.deepCopy()方法，以便在传递给(id)kCVPixelBufferIOSurfacePropertiesKey: @{}的属性词典中包含CVPixelBufferCreate键值对，那么它可能会有效。
答案 2 :(得分：0)
在手动创建CVPixelBuffer和CMSampleBuffer以创建包含CoreGraphics个别帧的视频时，我遇到了相同错误代码的问题。我可以使用AVAssetWriterInputPixelBufferAdaptor来解决问题，就像您在自己的回答中所建议的那样。出于某种原因，只有在实际设备上运行代码时才需要这样做。在模拟器上，手动创建缓冲区工作正常。
我注意到，由于其他原因，也会出现相同的错误代码AVFoundationErrorDomain Code -11800和NSOSStatusErrorDomain Code -12780，例如：
AVAssetWriter URL.init(fileURLWithPath:)而不是URL.init(string:)创建）。（为了完整起见，发布此代码，您的代码已正确处理此问题。）