如何减少使用UIImagePickerController创建的视频的文件大小？ [英] How can I reduce the file size of a video created with UIImagePickerController?

问题描述

我有一个应用程序，允许用户用 UIImagePickerController 录制视频，然后将其上传到YouTube。问题是，即使视频只有5秒钟长， UIImagePickerController 创建的视频文件也是巨大的。例如，5秒长的视频是16-20兆字节。我想保持在540或720质量的视频，但我想减少文件的大小。

我一直在试验AVFoundation和 AVAssetExportSession 尝试获取较小的文件大小。我试过以下代码：

  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！）; 
}]; 
  

但完全没有缩小文件大小。我知道我在做什么是可能的，因为在苹果的照片应用程序中，当您选择在YouTube上共享时，会自动处理视频文件，使其足够小以便上传。我想在我的应用程序中做同样的事情。

我怎样才能做到这一点？

$ c> AVCaptureSession 和 AVAssetWriter 您可以设置压缩设置：

<$ p AVVideoWidthKey：@（video_width），
AVVideoHeightKey：@（video_height），
AVVideoCompressionPropertiesKey：$ b $ {code> NSDictionary *设置= @ {AVVideoCodecKey：AVVideoCodecH264，
b @ {AVVideoAverageBitRateKey：@（desired_bitrate），
AVVideoProfileLevelKey：AVVideoProfileLevelH264Main31，/ *或者任何配置文件&您希望使用的级别* /
AVVideoMaxKeyFrameIntervalKey：@（desired_keyframe_interval）}};

AVAssetWriterInput * writer_input = [AVAssetWriterInput assetWriterInputWithMediaType：AVMediaTypeVideo outputSettings：settings];

编辑：我猜如果你坚持使用 UIImagePicker 来创建电影，你必须使用 AVAssetReader的 copyNextSampleBuffer 和 AVAssetWriter的 appendSampleBuffer 方法来完成转码。

I have an app that allows a user to record a video with UIImagePickerController and then upload it to YouTube. The problem is that the video file that UIImagePickerController creates is HUGE, even when the video is only 5 seconds long. For example, a 5 second long video is 16-20 megabytes. I want to keep the video in 540 or 720 quality, but I want to reduce the file size.

I've been experimenting with AVFoundation and AVAssetExportSession to try to get a smaller file size. I've tried the following code:

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!");
}];

But this hasn't reduced the file size at all. I know what I'm doing is possible because in Apple's Photos app, when you select "share on YouTube", will automatically process the video file so its small enough to upload. I want to do the same thing in my app.

How can I accomplish this?

解决方案

With AVCaptureSession and AVAssetWriter you can set the compression settings as such:

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];

Edit: I guess if you insist on using the UIImagePicker to create the movie in the first place, you'll have to use AVAssetReader's copyNextSampleBuffer and AVAssetWriter's appendSampleBuffer methods to do the transcode.

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