我有一个应用，允许用户使用UIImagePickerController录制视频，然后将其上传到YouTube。问题是UIImagePickerController创建的视频文件很大，即使视频只有5秒钟。例如，5秒长的视频是16-20兆字节。我想保持540或720质量的视频，但我想减小文件大小。
我一直在尝试使用AVFoundation和AVAssetExportSession来尝试获得更小的文件大小。我尝试过以下代码：
AVAsset *video = [AVAsset assetWithURL:videoURL];
AVAssetExportSession *exportSession = [AVAssetExportSession exportSessionWithAsset:video presetName:AVAssetExportPresetPassthrough];
exportSession.shouldOptimizeForNetworkUse = YES;
exportSession.outputFileType = AVFileTypeMPEG4;
exportSession.outputURL = [pathToSavedVideosDirectory URLByAppendingPathComponent:@"vid1.mp4"];
[exportSession exportAsynchronouslyWithCompletionHandler:^{
NSLog(@"done processing video!");
}];
但是这并没有减少文件大小。我知道我正在做的事情是可能的，因为在Apple的照片应用中，当你选择“在YouTube上分享”时，会自动处理视频文件，因此它的小到可以上传。我想在我的应用程序中做同样的事情。
我该如何做到这一点？
答案 0 :(得分：67)
使用AVCaptureSession和AVAssetWriter，您可以设置压缩设置：
NSDictionary *settings = @{AVVideoCodecKey:AVVideoCodecH264,
AVVideoWidthKey:@(video_width),
AVVideoHeightKey:@(video_height),
AVVideoCompressionPropertiesKey:
@{AVVideoAverageBitRateKey:@(desired_bitrate),
AVVideoProfileLevelKey:AVVideoProfileLevelH264Main31, /* Or whatever profile & level you wish to use */
AVVideoMaxKeyFrameIntervalKey:@(desired_keyframe_interval)}};
AVAssetWriterInput* writer_input = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];
修改：我想如果您坚持使用UIImagePicker来创建电影，则必须使用AVAssetReader's copyNextSampleBuffer和AVAssetWriter's { {1}}进行转码的方法。
答案 1 :(得分：21)
yourfriendzak是对的：设置cameraUI.videoQuality = UIImagePickerControllerQualityTypeLow;不是解决方案。解决方案是降低数据速率或比特率，这正是jgh所暗示的。
我有三种方法。第一种方法处理UIImagePicker委托方法：
// For responding to the user accepting a newly-captured picture or movie
- (void) imagePickerController: (UIImagePickerController *) picker didFinishPickingMediaWithInfo: (NSDictionary *) info {
// Handle movie capture
NSURL *movieURL = [info objectForKey:
UIImagePickerControllerMediaURL];
NSURL *uploadURL = [NSURL fileURLWithPath:[[NSTemporaryDirectory() stringByAppendingPathComponent:[self randomString]] stringByAppendingString:@".mp4"]];
// Compress movie first
[self convertVideoToLowQuailtyWithInputURL:movieURL outputURL:uploadURL];
}
第二种方法将视频转换为较低的比特率，而不是较低的维度。
- (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL
outputURL:(NSURL*)outputURL
{
//setup video writer
AVAsset *videoAsset = [[AVURLAsset alloc] initWithURL:inputURL options:nil];
AVAssetTrack *videoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
CGSize videoSize = videoTrack.naturalSize;
NSDictionary *videoWriterCompressionSettings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:1250000], AVVideoAverageBitRateKey, nil];
NSDictionary *videoWriterSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey, videoWriterCompressionSettings, AVVideoCompressionPropertiesKey, [NSNumber numberWithFloat:videoSize.width], AVVideoWidthKey, [NSNumber numberWithFloat:videoSize.height], AVVideoHeightKey, nil];
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoWriterSettings];
videoWriterInput.expectsMediaDataInRealTime = YES;
videoWriterInput.transform = videoTrack.preferredTransform;
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:outputURL fileType:AVFileTypeQuickTimeMovie error:nil];
[videoWriter addInput:videoWriterInput];
//setup video reader
NSDictionary *videoReaderSettings = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput *videoReaderOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:videoReaderSettings];
AVAssetReader *videoReader = [[AVAssetReader alloc] initWithAsset:videoAsset error:nil];
[videoReader addOutput:videoReaderOutput];
//setup audio writer
AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeAudio
outputSettings:nil];
audioWriterInput.expectsMediaDataInRealTime = NO;
[videoWriter addInput:audioWriterInput];
//setup audio reader
AVAssetTrack* audioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVAssetReaderOutput *audioReaderOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:audioTrack outputSettings:nil];
AVAssetReader *audioReader = [AVAssetReader assetReaderWithAsset:videoAsset error:nil];
[audioReader addOutput:audioReaderOutput];
[videoWriter startWriting];
//start writing from video reader
[videoReader startReading];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
dispatch_queue_t processingQueue = dispatch_queue_create("processingQueue1", NULL);
[videoWriterInput requestMediaDataWhenReadyOnQueue:processingQueue usingBlock:
^{
while ([videoWriterInput isReadyForMoreMediaData]) {
CMSampleBufferRef sampleBuffer;
if ([videoReader status] == AVAssetReaderStatusReading &&
(sampleBuffer = [videoReaderOutput copyNextSampleBuffer])) {
[videoWriterInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
}
else {
[videoWriterInput markAsFinished];
if ([videoReader status] == AVAssetReaderStatusCompleted) {
//start writing from audio reader
[audioReader startReading];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
dispatch_queue_t processingQueue = dispatch_queue_create("processingQueue2", NULL);
[audioWriterInput requestMediaDataWhenReadyOnQueue:processingQueue usingBlock:^{
while (audioWriterInput.readyForMoreMediaData) {
CMSampleBufferRef sampleBuffer;
if ([audioReader status] == AVAssetReaderStatusReading &&
(sampleBuffer = [audioReaderOutput copyNextSampleBuffer])) {
[audioWriterInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
}
else {
[audioWriterInput markAsFinished];
if ([audioReader status] == AVAssetReaderStatusCompleted) {
[videoWriter finishWritingWithCompletionHandler:^(){
[self sendMovieFileAtURL:outputURL];
}];
}
}
}
}
];
}
}
}
}
];
}
成功后，调用第三种方法sendMovieFileAtURL:，将outputURL的压缩视频上传到服务器。
请注意我已在项目中启用了ARC ，因此如果您的ARC已关闭，则必须添加一些release次来电。
答案 2 :(得分：19)
在UImagePickerController上，您拥有UIImagePickerControllerQualityType类型的videoQuality属性，并且会应用于录制的电影以及您从图书馆挑选的电影（在转码阶段）。
或者，如果您不必处理来自库的现有资产（文件），您可能需要查看这些预设：
AVAssetExportPresetLowQuality
AVAssetExportPresetMediumQuality
AVAssetExportPresetHighestQuality
和
AVAssetExportPreset640x480
AVAssetExportPreset960x540
AVAssetExportPreset1280x720
AVAssetExportPreset1920x1080
并将其中一个传递给AVAssetExportSession课程的initializer。我担心您必须使用那些针对您的特定内容的内容，因为没有关于low和medium质量或640x480或{1280x720的质量的准确描述{1}}预设。文档中唯一有用的信息如下：
导出适用于设备的QuickTime文件的预设名称 您可以使用这些导出选项生成具有适合当前设备的视频大小的QuickTime .mov文件。
导出不会从较小的尺寸缩放视频。使用H.264压缩视频;音频使用AAC压缩
某些设备无法支持某些尺寸。
除此之外，我不记得在 AVFoundation
我错了，有一种方法可以调整你提到的所有参数，确实是AVAssetWriter：How do I export UIImage array as a movie?
顺便说一句，这是一个带有代码示例的类似问题的链接：iPhone:Programmatically compressing recorded video to share?
答案 3 :(得分：12)
您需要博士才能使用AVAssetWriter - 这非常重要：https://developer.apple.com/library/mac/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/05_Export.html#//apple_ref/doc/uid/TP40010188-CH9-SW1
有一个令人惊叹的库，可以完全按照您的需要进行操作，这只是一个AVAssetExportSession直接替换，具有更重要的功能，如更改比特率：https://github.com/rs/SDAVAssetExportSession
以下是如何使用它：
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
SDAVAssetExportSession *encoder = [SDAVAssetExportSession.alloc initWithAsset:[AVAsset assetWithURL:[info objectForKey:UIImagePickerControllerMediaURL]]];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
self.myPathDocs = [documentsDirectory stringByAppendingPathComponent:
[NSString stringWithFormat:@"lowerBitRate-%d.mov",arc4random() % 1000]];
NSURL *url = [NSURL fileURLWithPath:self.myPathDocs];
encoder.outputURL=url;
encoder.outputFileType = AVFileTypeMPEG4;
encoder.shouldOptimizeForNetworkUse = YES;
encoder.videoSettings = @
{
AVVideoCodecKey: AVVideoCodecH264,
AVVideoCompressionPropertiesKey: @
{
AVVideoAverageBitRateKey: @2300000, // Lower bit rate here
AVVideoProfileLevelKey: AVVideoProfileLevelH264High40,
},
};
encoder.audioSettings = @
{
AVFormatIDKey: @(kAudioFormatMPEG4AAC),
AVNumberOfChannelsKey: @2,
AVSampleRateKey: @44100,
AVEncoderBitRateKey: @128000,
};
[encoder exportAsynchronouslyWithCompletionHandler:^
{
int status = encoder.status;
if (status == AVAssetExportSessionStatusCompleted)
{
AVAssetTrack *videoTrack = nil;
AVURLAsset *asset = [AVAsset assetWithURL:encoder.outputURL];
NSArray *videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];
videoTrack = [videoTracks objectAtIndex:0];
float frameRate = [videoTrack nominalFrameRate];
float bps = [videoTrack estimatedDataRate];
NSLog(@"Frame rate == %f",frameRate);
NSLog(@"bps rate == %f",bps/(1024.0 * 1024.0));
NSLog(@"Video export succeeded");
// encoder.outputURL <- this is what you want!!
}
else if (status == AVAssetExportSessionStatusCancelled)
{
NSLog(@"Video export cancelled");
}
else
{
NSLog(@"Video export failed with error: %@ (%d)", encoder.error.localizedDescription, encoder.error.code);
}
}];
}
答案 4 :(得分：7)
如果要将UIImagePickerController打开到以下任何一项，可以设置视频质量：
UIImagePickerControllerQualityType640x480
UIImagePickerControllerQualityTypeLow
UIImagePickerControllerQualityTypeMedium
UIImagePickerControllerQualityTypeHigh
UIImagePickerControllerQualityTypeIFrame960x540
UIImagePickerControllerQualityTypeIFrame1280x720
打开UIImagePickerController时，请尝试使用此代码更改质量类型：
if (([UIImagePickerController isSourceTypeAvailable:
UIImagePickerControllerSourceTypeCamera] == NO))
return NO;
UIImagePickerController *cameraUI = [[UIImagePickerController alloc] init];
cameraUI.sourceType = UIImagePickerControllerSourceTypeCamera;
cameraUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeMovie, nil];
cameraUI.allowsEditing = NO;
cameraUI.delegate = self;
cameraUI.videoQuality = UIImagePickerControllerQualityTypeLow;//you can change the quality here
[self presentModalViewController:cameraUI animated:YES];
答案 5 :(得分：7)
Erik Wegener代码重写为swift 3：
class func convertVideoToLowQuailtyWithInputURL(inputURL: NSURL, outputURL: NSURL, onDone: @escaping () -> ()) {
//setup video writer
let videoAsset = AVURLAsset(url: inputURL as URL, options: nil)
let videoTrack = videoAsset.tracks(withMediaType: AVMediaTypeVideo)[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: AVMediaTypeVideo, outputSettings: videoWriterSettings)
videoWriterInput.expectsMediaDataInRealTime = true
videoWriterInput.transform = videoTrack.preferredTransform
let videoWriter = try! AVAssetWriter(outputURL: outputURL as URL, fileType: AVFileTypeQuickTimeMovie)
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)
let videoReader = try! AVAssetReader(asset: videoAsset)
videoReader.add(videoReaderOutput)
//setup audio writer
let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio, outputSettings: nil)
audioWriterInput.expectsMediaDataInRealTime = false
videoWriter.add(audioWriterInput)
//setup audio reader
let audioTrack = videoAsset.tracks(withMediaType: AVMediaTypeAudio)[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: kCMTimeZero)
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: kCMTimeZero)
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
onDone();
})
}
}
}
})
}
}
}
})
}
答案 6 :(得分：3)
Erik Wegener代码重写为swift：
class func convertVideoToLowQuailtyWithInputURL(inputURL: NSURL, outputURL: NSURL, onDone: () -> ()) {
//setup video writer
let videoAsset = AVURLAsset(URL: inputURL, options: nil)
let videoTrack = videoAsset.tracksWithMediaType(AVMediaTypeVideo)[0]
let videoSize = videoTrack.naturalSize
let videoWriterCompressionSettings = [
AVVideoAverageBitRateKey : Int(125000)
]
let videoWriterSettings:[String : AnyObject] = [
AVVideoCodecKey : AVVideoCodecH264,
AVVideoCompressionPropertiesKey : videoWriterCompressionSettings,
AVVideoWidthKey : Int(videoSize.width),
AVVideoHeightKey : Int(videoSize.height)
]
let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoWriterSettings)
videoWriterInput.expectsMediaDataInRealTime = true
videoWriterInput.transform = videoTrack.preferredTransform
let videoWriter = try! AVAssetWriter(URL: outputURL, fileType: AVFileTypeQuickTimeMovie)
videoWriter.addInput(videoWriterInput)
//setup video reader
let videoReaderSettings:[String : AnyObject] = [
kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange)
]
let videoReaderOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings)
let videoReader = try! AVAssetReader(asset: videoAsset)
videoReader.addOutput(videoReaderOutput)
//setup audio writer
let audioWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio, outputSettings: nil)
audioWriterInput.expectsMediaDataInRealTime = false
videoWriter.addInput(audioWriterInput)
//setup audio reader
let audioTrack = videoAsset.tracksWithMediaType(AVMediaTypeAudio)[0]
let audioReaderOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: nil)
let audioReader = try! AVAssetReader(asset: videoAsset)
audioReader.addOutput(audioReaderOutput)
videoWriter.startWriting()
//start writing from video reader
videoReader.startReading()
videoWriter.startSessionAtSourceTime(kCMTimeZero)
let processingQueue = dispatch_queue_create("processingQueue1", nil)
videoWriterInput.requestMediaDataWhenReadyOnQueue(processingQueue, usingBlock: {() -> Void in
while videoWriterInput.readyForMoreMediaData {
let sampleBuffer:CMSampleBuffer? = videoReaderOutput.copyNextSampleBuffer();
if videoReader.status == .Reading && sampleBuffer != nil {
videoWriterInput.appendSampleBuffer(sampleBuffer!)
}
else {
videoWriterInput.markAsFinished()
if videoReader.status == .Completed {
//start writing from audio reader
audioReader.startReading()
videoWriter.startSessionAtSourceTime(kCMTimeZero)
let processingQueue = dispatch_queue_create("processingQueue2", nil)
audioWriterInput.requestMediaDataWhenReadyOnQueue(processingQueue, usingBlock: {() -> Void in
while audioWriterInput.readyForMoreMediaData {
let sampleBuffer:CMSampleBufferRef? = audioReaderOutput.copyNextSampleBuffer()
if audioReader.status == .Reading && sampleBuffer != nil {
audioWriterInput.appendSampleBuffer(sampleBuffer!)
}
else {
audioWriterInput.markAsFinished()
if audioReader.status == .Completed {
videoWriter.finishWritingWithCompletionHandler({() -> Void in
onDone();
})
}
}
}
})
}
}
}
})
}
答案 7 :(得分：3)
Swift 5 和 Good quality
的代码以下是根据this link中的代码进行操作的方法。链接的问题在于它仅适用于.mov文件输出，如果要输出.mp4文件，它将崩溃。以下代码可让您获得.mp4输出。它经过尝试，测试和运行。例如，原本为27mb的15秒视频减少为2mb。如果您想要更好的质量，请提高bitrate。我将其设置为 1250000 。
c + p此代码：
import AVFoundation
// add these properties
var assetWriter: AVAssetWriter!
var assetWriterVideoInput: AVAssetWriterInput!
var audioMicInput: AVAssetWriterInput!
var videoURL: URL!
var audioAppInput: AVAssetWriterInput!
var channelLayout = AudioChannelLayout()
var assetReader: AVAssetReader?
let bitrate: NSNumber = NSNumber(value: 1250000) // *** you can change this number to increase/decrease the quality. The more you increase, the better the video quality but the the compressed file size will also increase
// compression function, it returns a .mp4 but you can change it to .mov inside the do try block towards the middle. Change assetWriter = try AVAssetWriter ... AVFileType.mp4 to AVFileType.mov
func compressFile(_ urlToCompress: URL, completion:@escaping (URL)->Void) {
var audioFinished = false
var videoFinished = false
let asset = AVAsset(url: urlToCompress)
//create asset reader
do {
assetReader = try AVAssetReader(asset: asset)
} catch {
assetReader = nil
}
guard let reader = assetReader else {
print("Could not iniitalize asset reader probably failed its try catch")
// show user error message/alert
return
}
guard let videoTrack = asset.tracks(withMediaType: AVMediaType.video).first else { return }
let videoReaderSettings: [String:Any] = [kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_32ARGB]
let assetReaderVideoOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: videoReaderSettings)
var assetReaderAudioOutput: AVAssetReaderTrackOutput?
if let audioTrack = asset.tracks(withMediaType: AVMediaType.audio).first {
let audioReaderSettings: [String : Any] = [
AVFormatIDKey: kAudioFormatLinearPCM,
AVSampleRateKey: 44100,
AVNumberOfChannelsKey: 2
]
assetReaderAudioOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: audioReaderSettings)
if reader.canAdd(assetReaderAudioOutput!) {
reader.add(assetReaderAudioOutput!)
} else {
print("Couldn't add audio output reader")
// show user error message/alert
return
}
}
if reader.canAdd(assetReaderVideoOutput) {
reader.add(assetReaderVideoOutput)
} else {
print("Couldn't add video output reader")
// show user error message/alert
return
}
let videoSettings:[String:Any] = [
AVVideoCompressionPropertiesKey: [AVVideoAverageBitRateKey: self.bitrate],
AVVideoCodecKey: AVVideoCodecType.h264,
AVVideoHeightKey: videoTrack.naturalSize.height,
AVVideoWidthKey: videoTrack.naturalSize.width,
AVVideoScalingModeKey: AVVideoScalingModeResizeAspectFill
]
let audioSettings: [String:Any] = [AVFormatIDKey : kAudioFormatMPEG4AAC,
AVNumberOfChannelsKey : 2,
AVSampleRateKey : 44100.0,
AVEncoderBitRateKey: 128000
]
let audioInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: audioSettings)
let videoInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: videoSettings)
videoInput.transform = videoTrack.preferredTransform
let videoInputQueue = DispatchQueue(label: "videoQueue")
let audioInputQueue = DispatchQueue(label: "audioQueue")
do {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"
let date = Date()
let tempDir = NSTemporaryDirectory()
let outputPath = "\(tempDir)/\(formatter.string(from: date)).mp4"
let outputURL = URL(fileURLWithPath: outputPath)
assetWriter = try AVAssetWriter(outputURL: outputURL, fileType: AVFileType.mp4)
} catch {
assetWriter = nil
}
guard let writer = assetWriter else {
print("assetWriter was nil")
// show user error message/alert
return
}
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: { [weak self] in
if let assetWriter = self?.assetWriter {
do {
let data = try Data(contentsOf: assetWriter.outputURL)
print("compressFile -file size after compression: \(Double(data.count / 1048576)) mb")
} catch let err as NSError {
print("compressFile Error: \(err.localizedDescription)")
}
}
completion((self?.assetWriter?.outputURL)!)
})
self.assetReader?.cancelReading()
}
}
audioInput.requestMediaDataWhenReady(on: audioInputQueue) {
while(audioInput.isReadyForMoreMediaData) {
if let cmSampleBuffer = assetReaderAudioOutput?.copyNextSampleBuffer() {
audioInput.append(cmSampleBuffer)
} else {
audioInput.markAsFinished()
DispatchQueue.main.async {
audioFinished = true
closeWriter()
}
break;
}
}
}
videoInput.requestMediaDataWhenReady(on: videoInputQueue) {
// request data here
while(videoInput.isReadyForMoreMediaData) {
if let cmSampleBuffer = assetReaderVideoOutput.copyNextSampleBuffer() {
videoInput.append(cmSampleBuffer)
} else {
videoInput.markAsFinished()
DispatchQueue.main.async {
videoFinished = true
closeWriter()
}
break;
}
}
}
}
在压缩URL时，这里是使用方法。 compressedURL 在回调内返回：
@IBAction func buttonTapped(sender: UIButton) {
// show activity indicator
let videoURL = URL(string: "...")
compressFile(videoURL) { (compressedURL) in
// remove activity indicator
// do something with the compressedURL such as sending to Firebase or playing it in a player on the *main queue*
}
}
如果要压缩混合成分，请执行以下操作。您将需要使用上面的AVMutableComposition，AVAssetExportSession和compressFile(:completion:)函数：
@IBAction func buttonTapped(sender: UIButton) {
// show activity indicator
let mixComposition = AVMutableComposition()
// code to create mix ...
// create a local file
let tempDir = NSTemporaryDirectory()
let dirPath = "\(tempDir)/videos_\(UUID().uuidString).mp4"
let outputFileURL = URL(fileURLWithPath: dirPath)
removeUrlFromFileManager(outputFileURL) // check to see if the file already exists, if it does remove it, code is at the bottom of the answer
createAssetExportSession(mixComposition, outputFileURL)
}
// here is the AssetExportSession function with the compressFile(:completion:) inside the callback
func createAssetExportSession(_ mixComposition: AVMutableComposition, _ outputFileURL: URL) {
// *** If your video/url doesn't have sound (not mute but literally no sound, my iPhone's mic was broken when I recorded the video), change this to use AVAssetExportPresetPassthrough instead of HighestQulity. When my video didn't have sound the exporter.status kept returning .failed *** You can check for sound using https://stackoverflow.com/a/64733623/4833705
guard let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) else {
// alert user there is a problem
return
}
exporter.outputURL = outputFileURL
exporter.outputFileType = AVFileType.mp4
exporter.shouldOptimizeForNetworkUse = true
exporter.exportAsynchronously {
switch exporter.status {
case .completed:
print("completed")
// view the AssetExportSession file size using HighestQuality which will be very high
do {
let data = try Data(contentsOf: outputFileURL)
print("createAssetExportSession -file size: \(Double(data.count / 1048576)) mb")
} catch let err as NSError {
print("createAssetExportSession Error: \(err.localizedDescription)")
}
case .failed:
print("failed:", exporter.error as Any)
DispatchQueue.main.async { [weak self] in
// remove activity indicator
// alert user there is a problem
}
return
case .cancelled:
print("cancelled", exporter.error as Any)
DispatchQueue.main.async { [weak self] in
// remove activity indicator
// alert user there is a problem
}
return
default:
print("complete")
}
guard let exporterOutputURL = exporter.outputURL else {
// alert user there is a problem
return
}
DispatchQueue.main.async { [weak self] in
self?.compressFile(exporterOutputURL) { (compressedURL) in
// remove activity indicator
// do something with the compressedURL such as sending to Firebase or playing it in a player on the *main queue*
}
}
}
}
在完成压缩后，确保从文件系统中删除CompressedURL，例如在关闭vc之前
func dismissVC() {
removeUrlFromFileManager(compressedURL)
// dismiss vc ...
}
removeUrlFromFileManager(_ outputFileURL: URL?) {
if let outputFileURL = outputFileURL {
let path = outputFileURL.path
if FileManager.default.fileExists(atPath: path) {
do {
try FileManager.default.removeItem(atPath: path)
print("url SUCCESSFULLY removed: \(outputFileURL)")
} catch {
print("Could not remove file at url: \(outputFileURL)")
}
}
}
}
答案 8 :(得分：1)
有一个很棒的自定义类（SDAVAssetExportSession）来进行视频压缩。您可以从此link下载。
下载后，将SDAVAssetExportSession.h和SDAVAssetExportSession.m文件添加到项目中，然后使用下面的代码进行压缩。 在下面的代码中，您可以通过指定分辨率和比特率来压缩视频
#import "SDAVAssetExportSession.h"
- (void)compressVideoWithInputVideoUrl:(NSURL *) inputVideoUrl
{
/* Create Output File Url */
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *finalVideoURLString = [documentsDirectory stringByAppendingPathComponent:@"compressedVideo.mp4"];
NSURL *outputVideoUrl = ([[NSURL URLWithString:finalVideoURLString] isFileURL] == 1)?([NSURL URLWithString:finalVideoURLString]):([NSURL fileURLWithPath:finalVideoURLString]); // Url Should be a file Url, so here we check and convert it into a file Url
SDAVAssetExportSession *compressionEncoder = [SDAVAssetExportSession.alloc initWithAsset:[AVAsset assetWithURL:inputVideoUrl]]; // provide inputVideo Url Here
compressionEncoder.outputFileType = AVFileTypeMPEG4;
compressionEncoder.outputURL = outputVideoUrl; //Provide output video Url here
compressionEncoder.videoSettings = @
{
AVVideoCodecKey: AVVideoCodecH264,
AVVideoWidthKey: @800, //Set your resolution width here
AVVideoHeightKey: @600, //set your resolution height here
AVVideoCompressionPropertiesKey: @
{
AVVideoAverageBitRateKey: @45000, // Give your bitrate here for lower size give low values
AVVideoProfileLevelKey: AVVideoProfileLevelH264High40,
},
};
compressionEncoder.audioSettings = @
{
AVFormatIDKey: @(kAudioFormatMPEG4AAC),
AVNumberOfChannelsKey: @2,
AVSampleRateKey: @44100,
AVEncoderBitRateKey: @128000,
};
[compressionEncoder exportAsynchronouslyWithCompletionHandler:^
{
if (compressionEncoder.status == AVAssetExportSessionStatusCompleted)
{
NSLog(@"Compression Export Completed Successfully");
}
else if (compressionEncoder.status == AVAssetExportSessionStatusCancelled)
{
NSLog(@"Compression Export Canceled");
}
else
{
NSLog(@"Compression Failed");
}
}];
}
取消压缩使用以下代码行
[compressionEncoder cancelExport]; //Video compression cancel
答案 9 :(得分：1)
我支持 etayluz 的回答SDAVAssetExportSession是一个很棒的自定义类来进行视频压缩。这是我的工作代码。您可以从此link下载 SDAVAssetExportSession 。
下载后，将SDAVAssetExportSession.h和SDAVAssetExportSession.m文件添加到项目中，然后使用下面的代码进行压缩。 在下面的代码中，您可以通过指定分辨率和比特率来压缩视频
#import "SDAVAssetExportSession.h"
- (void)compressVideoWithInputVideoUrl:(NSURL *) inputVideoUrl
{
/* Create Output File Url */
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *finalVideoURLString = [documentsDirectory stringByAppendingPathComponent:@"compressedVideo.mp4"];
NSURL *outputVideoUrl = ([[NSURL URLWithString:finalVideoURLString] isFileURL] == 1)?([NSURL URLWithString:finalVideoURLString]):([NSURL fileURLWithPath:finalVideoURLString]); // Url Should be a file Url, so here we check and convert it into a file Url
SDAVAssetExportSession *compressionEncoder = [SDAVAssetExportSession.alloc initWithAsset:[AVAsset assetWithURL:inputVideoUrl]]; // provide inputVideo Url Here
compressionEncoder.outputFileType = AVFileTypeMPEG4;
compressionEncoder.outputURL = outputVideoUrl; //Provide output video Url here
compressionEncoder.videoSettings = @
{
AVVideoCodecKey: AVVideoCodecH264,
AVVideoWidthKey: @800, //Set your resolution width here
AVVideoHeightKey: @600, //set your resolution height here
AVVideoCompressionPropertiesKey: @
{
AVVideoAverageBitRateKey: @45000, // Give your bitrate here for lower size give low values
AVVideoProfileLevelKey: AVVideoProfileLevelH264High40,
},
};
compressionEncoder.audioSettings = @
{
AVFormatIDKey: @(kAudioFormatMPEG4AAC),
AVNumberOfChannelsKey: @2,
AVSampleRateKey: @44100,
AVEncoderBitRateKey: @128000,
};
[compressionEncoder exportAsynchronouslyWithCompletionHandler:^
{
if (compressionEncoder.status == AVAssetExportSessionStatusCompleted)
{
NSLog(@"Compression Export Completed Successfully");
}
else if (compressionEncoder.status == AVAssetExportSessionStatusCancelled)
{
NSLog(@"Compression Export Canceled");
}
else
{
NSLog(@"Compression Failed");
}
}];
}
取消压缩使用以下代码行
[compressionEncoder cancelExport]; //Video compression cancel
答案 10 :(得分：0)
迅速4：
func convertVideoToLowQuailtyWithInputURL(inputURL: NSURL, outputURL: NSURL, completion: @escaping (Bool) -> 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)
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 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: kCMTimeZero)
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: kCMTimeZero)
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)
})
}
}
}
})
}
}
}
})
}
答案 11 :(得分：0)
Use exportSession.fileLengthLimit = 1048576 * 10 //10 MB
10MB是硬编码号码。根据所需的比特率使用。
fileLengthLimit
会话数不应超过。取决于来源的内容 资产，输出可能会略大于文件 长度限制。如果您要检查输出文件的长度 要求在使用前必须遵守严格的限制 输出。另请参见maxDuration和timeRange。指示
输出的文件长度