如何将期望的帧速率设置为AVAssetWriterInput [英] How to set expected framerate to AVAssetWriterInput

问题描述

我有一个应用程序，可以用不同的方式对视频进行编码并将其保存到照片库-它可以剪切特定的时间范围，添加图片，文本等.一切正常，直到我尝试对120 fps以上的视频进行编码.问题在于视频似乎动作缓慢，我根本不追求这个目标.

I have an app which encodes videos in different ways and saves it to Photos library - it can cut specific time range, add pictures, text, etc. Everything is working perfectly till I try to encode video 120+ fps. The problem is that video appears to be slow-motioned and I don't pursue that goal at all.

在这里关于 AVAssetWritterInput 的属性(称为 AVVideoExpectedSourceFrameRateKey )，但问题是当我尝试将此参数应用于我的 AVAssetWritterInput 时，我出现此错误:

Here I found out about property for AVAssetWritterInput which is called AVVideoExpectedSourceFrameRateKey, but the problem is that when I try to apply this parameter to my AVAssetWritterInput, I'm getting this error:

***由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因:'***-[AVAssetWriterInput initWithMediaType:outputSettings:sourceFormatHint:]输出设置字典包含一个或多个无效键:ExpectedFrameRate'

这是我的 AVAssetWriterInput 初始化，一点都不花哨:

Here's my AVAssetWriterInput initialization, nothing fancy at all:

let input = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: [AVVideoCodecKey: AVVideoCodecJPEG,
                                                                                         AVVideoHeightKey: correctedContentSize.height,
                                                                                         AVVideoWidthKey: correctedContentSize.width,
                                                                                         AVVideoExpectedSourceFrameRateKey: 60])

任何帮助将不胜感激.谢谢.

Any help would be appreciated. Thanks.

推荐答案

问题出在您将关键字放在字典"中以将设置加载到outputSettings中的方式.实际上，键"AVVideoExpectedSourceFrameRateKey"应该放在嵌套的Dictionary中，并且键是"AVVideoCompressionPropertiesKey".因此，您可以使用类似于Dictionary的Dictionary作为outputSettings.它应该看起来像这样:

The problem comes from the way you're placing the key inside of your Dictionary to load the settings into the outputSettings. The key 'AVVideoExpectedSourceFrameRateKey' is actually supposed to go inside a nested Dictionary, and the key for it is 'AVVideoCompressionPropertiesKey'. So you have a Dictionary of Dictionaries of sorts as the outputSettings instead. It should look something like this:

let outputSettings:[String: Any] = [
            AVVideoCodecKey: AVVideoCodecJPEG,
            AVVideoHeightKey: correctedContentSize.height,
            AVVideoWidthKey: correctedContentSize.width
            AVVideoCompressionPropertiesKey: 
               [AVVideoExpectedSourceFrameRateKey: 60]                                         
        ]

如果您想在回放视频时使用它来调整Feed，可以在此处找到有关此过程的更多信息:

More info on this process can be found here if you'd like to use this to adjust the feed when playing this video back:

AVAssetWriter AVVideoExpectedSourceFrameRateKey(帧速率)已忽略

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