我一直致力于 iOS Swift 中的视频压缩，并关注this https://stackoverflow.com/a/52346800/9250384所以的答案。它工作正常，直到我将这段代码的文件格式更改为.mp4
let videoWriter = try! AVAssetWriter(outputURL: outputURL as URL, fileType: AVFileType.mov)
我需要输出是有原因的.mp4文件格式。所以当我这样做时，应用程序就会崩溃。并给我这个错误，
2020-04-27 18:20:52.573614+0500 BrightCaster[7847:1513728] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[AVAssetWriter addInput:] In order to perform passthrough to file type public.mpeg-4, please provide a format hint in the AVAssetWriterInput initializer'
*** First throw call stack:
(0x1b331d5f0 0x1b303fbcc 0x1bd53b2b0 0x102383c0c 0x102382164 0x1021897cc 0x1b6ca73bc 0x1b6caba7c 0x1b6daec94 0x1b7835080 0x1b7834d30 0x1e9d077b4 0x1b786a764 0x1b783eb68 0x1b783f070 0x1e9d468f4 0x1b783f1c0 0x1e9d468f4 0x1b9e21d9c 0x105173730 0x105181710 0x1b329b748 0x1b329661c 0x1b3295c34 0x1bd3df38c 0x1b73c822c 0x10230f8a0 0x1b311d800)
libc++abi.dylib: terminating with uncaught exception of type NSException
所以我搜索了SO并发现this https://stackoverflow.com/q/45539990/9250384与我的问题相关的问题。
但现在的问题是当我尝试添加它时answer https://stackoverflow.com/a/55073239/9250384对于我的函数，它给了我错误anAudioSampleBuffer 未定义。由于我对音频/视频领域完全陌生，我无法理解为什么它给了我这个。以及如何解决这个问题。
我在函数中添加的答案中的代码如下。
//setup audio writer
//let formatDesc = CMSampleBufferGetFormatDescription(anAudioSampleBuffer)
//let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil, sourceFormatHint: formatDesc)
let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)
audioWriterInput.expectsMediaDataInRealTime = false
videoWriter.add(audioWriterInput)
评论部分不起作用。任何帮助将不胜感激谢谢。
整个转换函数如下
func convertVideoToLowQuailtyWithInputURL(inputURL: URL, outputURL: URL, completion: @escaping (Bool , _ url: String) -> Void) {
let videoAsset = AVURLAsset(url: inputURL as URL, options: nil)
let videoTrack = videoAsset.tracks(withMediaType: AVMediaType.video)[0]
let videoSize = videoTrack.naturalSize
let videoWriterCompressionSettings = [
AVVideoAverageBitRateKey : Int(125000)
]
let videoWriterSettings:[String : AnyObject] = [
AVVideoCodecKey : AVVideoCodecH264 as AnyObject,
AVVideoCompressionPropertiesKey : videoWriterCompressionSettings as AnyObject,
AVVideoWidthKey : Int(videoSize.width) as AnyObject,
AVVideoHeightKey : Int(videoSize.height) as AnyObject
]
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: videoWriterSettings)
videoWriterInput.expectsMediaDataInRealTime = true
videoWriterInput.transform = videoTrack.preferredTransform
let videoWriter = try! AVAssetWriter(outputURL: outputURL as URL, fileType: AVFileType.mov) // for now its converting in .mov I THINK SO.
videoWriter.add(videoWriterInput)
//setup video reader
let videoReaderSettings:[String : AnyObject] = [
kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange) as AnyObject
]
let videoReaderOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings)
var videoReader: AVAssetReader!
do{
videoReader = try AVAssetReader(asset: videoAsset)
}
catch {
print("video reader error: \(error)")
completion(false, "")
}
videoReader.add(videoReaderOutput)
//setup audio writer
//let formatDesc = CMSampleBufferGetFormatDescription(anAudioSampleBuffer) // this is giving me error here of un initilize, which I didn't I know.
//let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil, sourceFormatHint: formatDesc)
let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)
audioWriterInput.expectsMediaDataInRealTime = false
videoWriter.add(audioWriterInput)
//setup audio reader
let audioTrack = videoAsset.tracks(withMediaType: AVMediaType.audio)[0]
let audioReaderOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: nil)
let audioReader = try! AVAssetReader(asset: videoAsset)
audioReader.add(audioReaderOutput)
videoWriter.startWriting()
//start writing from video reader
videoReader.startReading()
videoWriter.startSession(atSourceTime: CMTime.zero)
let processingQueue = DispatchQueue(label: "processingQueue1")
videoWriterInput.requestMediaDataWhenReady(on: processingQueue, using: {() -> Void in
while videoWriterInput.isReadyForMoreMediaData {
let sampleBuffer:CMSampleBuffer? = videoReaderOutput.copyNextSampleBuffer();
if videoReader.status == .reading && sampleBuffer != nil {
videoWriterInput.append(sampleBuffer!)
}
else {
videoWriterInput.markAsFinished()
if videoReader.status == .completed {
//start writing from audio reader
audioReader.startReading()
videoWriter.startSession(atSourceTime: CMTime.zero)
let processingQueue = DispatchQueue(label: "processingQueue2")
audioWriterInput.requestMediaDataWhenReady(on: processingQueue, using: {() -> Void in
while audioWriterInput.isReadyForMoreMediaData {
let sampleBuffer:CMSampleBuffer? = audioReaderOutput.copyNextSampleBuffer()
if audioReader.status == .reading && sampleBuffer != nil {
audioWriterInput.append(sampleBuffer!)
}
else {
audioWriterInput.markAsFinished()
if audioReader.status == .completed {
videoWriter.finishWriting(completionHandler: {() -> Void in
completion(true, "\(videoWriter.outputURL)")
})
}
}
}
})
}
}
}
})
}
