TLDR：跳至更新。我正在寻找一种压缩或降低视频输出质量的方法，最好不要在创建后立即进行，但是如果那是唯一的方法，那么就这样
此外，如果您知道有什么好的可可豆荚可以做到这一点，那就很好了。
我正在寻找一个可以输出压缩URL的函数，并且我应该能够控制压缩质量...
尝试使函数在当前状态下工作后，它不起作用。 Yeilding nil。我认为是由于以下原因：
let outputURL = urlToCompress
assetWriter = try AVAssetWriter(outputURL: outputURL, fileType: AVFileType.mov)
我正在尝试快速压缩视频。到目前为止，所有解决方案都已在创建过程中使用。我想知道创建后是否有压缩方式？仅使用视频网址？
如果没有，那我该如何做一个压缩功能来压缩视频并返回压缩的URL？
我一直在使用的代码：
func compressVideo(videoURL: URL) -> URL {
let data = NSData(contentsOf: videoURL as URL)!
print("File size before compression: \(Double(data.length / 1048576)) mb")
let compressedURL = NSURL.fileURL(withPath: NSTemporaryDirectory() + NSUUID().uuidString + ".mov")
compressVideoHelperMethod(inputURL: videoURL , outputURL: compressedURL) { (exportSession) in
}
return compressedURL
}
func compressVideoHelperMethod(inputURL: URL, outputURL: URL, handler:@escaping (_ exportSession: AVAssetExportSession?)-> Void) {
let urlAsset = AVURLAsset(url: inputURL, options: nil)
guard let exportSession = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetMediumQuality) else {
handler(nil)
return
}
exportSession.outputURL = outputURL
exportSession.outputFileType = AVFileType.mov
exportSession.shouldOptimizeForNetworkUse = true
exportSession.exportAsynchronously { () -> Void in
handler(exportSession)
}
}
所以我找到了下面的代码。我尚未对其进行测试，但是我不知道如何制作，以便选择压缩质量：
var assetWriter:AVAssetWriter?
var assetReader:AVAssetReader?
let bitrate:NSNumber = NSNumber(value:250000)
func compressFile(urlToCompress: URL, outputURL: URL, completion:@escaping (URL)->Void){
//video file to make the asset
var audioFinished = false
var videoFinished = false
let asset = AVAsset(url: urlToCompress);
let duration = asset.duration
let durationTime = CMTimeGetSeconds(duration)
print("Video Actual Duration -- \(durationTime)")
//create asset reader
do{
assetReader = try AVAssetReader(asset: asset)
} catch{
assetReader = nil
}
guard let reader = assetReader else{
fatalError("Could not initalize asset reader probably failed its try catch")
}
let videoTrack = asset.tracks(withMediaType: AVMediaType.video).first!
let audioTrack = asset.tracks(withMediaType: AVMediaType.audio).first!
let videoReaderSettings: [String:Any] = [(kCVPixelBufferPixelFormatTypeKey as String?)!:kCVPixelFormatType_32ARGB ]
// ADJUST BIT RATE OF VIDEO HERE
if #available(iOS 11.0, *) {
let videoSettings:[String:Any] = [
AVVideoCompressionPropertiesKey: [AVVideoAverageBitRateKey:self.bitrate],
AVVideoCodecKey: AVVideoCodecType.h264,
AVVideoHeightKey: videoTrack.naturalSize.height,
AVVideoWidthKey: videoTrack.naturalSize.width
]
} else {
// Fallback on earlier versions
}
let assetReaderVideoOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings)
let assetReaderAudioOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: nil)
if reader.canAdd(assetReaderVideoOutput){
reader.add(assetReaderVideoOutput)
}else{
fatalError("Couldn't add video output reader")
}
if reader.canAdd(assetReaderAudioOutput){
reader.add(assetReaderAudioOutput)
}else{
fatalError("Couldn't add audio output reader")
}
let audioInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)
let videoInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: videoReaderSettings)
videoInput.transform = videoTrack.preferredTransform
//we need to add samples to the video input
let videoInputQueue = DispatchQueue(label: "videoQueue")
let audioInputQueue = DispatchQueue(label: "audioQueue")
do{
assetWriter = try AVAssetWriter(outputURL: outputURL, fileType: AVFileType.mov)
}catch{
assetWriter = nil
}
guard let writer = assetWriter else{
fatalError("assetWriter was nil")
}
writer.shouldOptimizeForNetworkUse = true
writer.add(videoInput)
writer.add(audioInput)
writer.startWriting()
reader.startReading()
writer.startSession(atSourceTime: CMTime.zero)
let closeWriter:()->Void = {
if (audioFinished && videoFinished){
self.assetWriter?.finishWriting(completionHandler: {
print("------ Finish Video Compressing")
completion((self.assetWriter?.outputURL)!)
})
self.assetReader?.cancelReading()
}
}
audioInput.requestMediaDataWhenReady(on: audioInputQueue) {
while(audioInput.isReadyForMoreMediaData){
let sample = assetReaderAudioOutput.copyNextSampleBuffer()
if (sample != nil){
audioInput.append(sample!)
}else{
audioInput.markAsFinished()
DispatchQueue.main.async {
audioFinished = true
closeWriter()
}
break;
}
}
}
videoInput.requestMediaDataWhenReady(on: videoInputQueue) {
//request data here
while(videoInput.isReadyForMoreMediaData){
let sample = assetReaderVideoOutput.copyNextSampleBuffer()
if (sample != nil){
let timeStamp = CMSampleBufferGetPresentationTimeStamp(sample!)
let timeSecond = CMTimeGetSeconds(timeStamp)
let per = timeSecond / durationTime
print("Duration --- \(per)")
videoInput.append(sample!)
}else{
videoInput.markAsFinished()
DispatchQueue.main.async {
videoFinished = true
closeWriter()
}
break;
}
}
}
}
如何更改此设置以设置质量？我正在寻找约0.6的压缩率
我现在正在处理以下代码，问题是它不断显示错误（似乎不起作用）：
func convertVideoToLowQuailty(withInputURL inputURL: URL?, outputURL: URL?, handler: @escaping (AVAssetExportSession?) -> Void) {
do {
if let outputURL = outputURL {
try FileManager.default.removeItem(at: outputURL)
}
} catch {
}
var asset: AVURLAsset? = nil
if let inputURL = inputURL {
asset = AVURLAsset(url: inputURL, options: nil)
}
var exportSession: AVAssetExportSession? = nil
if let asset = asset {
exportSession = AVAssetExportSession(asset: asset, presetName:AVAssetExportPresetMediumQuality)
}
exportSession?.outputURL = outputURL
exportSession?.outputFileType = .mov
exportSession?.exportAsynchronously(completionHandler: {
handler(exportSession)
})
}
func compressVideo(videoURL: URL) -> URL {
var outputURL = URL(fileURLWithPath: "/Users/alexramirezblonski/Desktop/output.mov")
convertVideoToLowQuailty(withInputURL: videoURL, outputURL: outputURL, handler: { exportSession in
print("fdshljfhdlasjkfdhsfsdljk")
if exportSession?.status == .completed {
print("completed\n", exportSession!.outputURL!)
outputURL = exportSession!.outputURL!
} else {
print("error\n")
outputURL = exportSession!.outputURL!//this needs to be fixed and may cause errors
}
})
return outputURL
}
答案 0 :(得分：3)
我查看了您的代码。实际上，您正在压缩中等质量的视频，其质量与原始视频大致相同。因此，您必须在导出会话初始化中更改presetName，如下所示：
exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetLowQuality)
您可以传递AVAssetExportPresetMediumQuality，因此可以按预期进行压缩。
以下列出了可用于压缩视频的格式。
1。在iOS 11.0中可用
2。在iOS 4.0中可用
您可以根据需要使用所有格式来压缩视频。 希望对您有帮助。