swift 使用帧方法的慢动作视频与音频- iOS

rta7y2nd 于 2024-01-05 发布在 Swift

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我必须转换视频到慢动作与音频使用帧基地的方法。以下链接是很多帮助是Reverse-AVAsset-Efficient
在解决方案中，我可以改变缓冲区的时间戳，实现慢动作视频。

for sample in videoSamples {
   var presentationTime = CMSampleBufferGetPresentationTimeStamp(sample)
   //Changing Timestamp to achieve slow-motion 
   presentationTime.timescale = presentationTime.timescale * 2
   let imageBufferRef = CMSampleBufferGetImageBuffer(sample)
   while !videoWriterInput.isReadyForMoreMediaData {
     Thread.sleep(forTimeInterval: 0.1)
   }
   pixelBufferAdaptor.append(imageBufferRef!, withPresentationTime: presentationTime)
}

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对于音频慢动作，我试图更改音频样本的时间戳，但没有效果。
是否有任何解决方案音频慢动作。
如果你有解决方案，请随时发布。谢谢。

swift

来源：https://stackoverflow.com/questions/61475524/slow-motion-video-with-audio-using-frames-approach-ios

3条答案

按热度按时间

hwazgwia1#

你可以使用AVMutableComposition来做一个简单的慢动作。正如@hotpaw2所提到的，有不止一种方法可以减慢你的音频-例如，你可以降低音调或保持恒定。这个解决方案似乎可以保持恒定，我看不出有任何方法可以改变这一点。也许这就是你想要的。也许不是。
您可以使用AVAssetExportSession将慢动作视频写入文件，由于AVMutableComposition是AVAsset的子类（可能令人惊讶），因此即使您尚未导出视频的慢动作版本，也可以使用AVPlayer预览结果。

let asset = AVURLAsset(url: Bundle.main.url(forResource: "video", withExtension: "mp4")! , options : nil)
let srcVideoTrack = asset.tracks(withMediaType: .video).first!
let srcAudioTrack = asset.tracks(withMediaType: .audio).first!
let sloMoComposition = AVMutableComposition()
let sloMoVideoTrack = sloMoComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!
let sloMoAudioTrack = sloMoComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)!
let assetTimeRange = CMTimeRange(start: .zero, duration: asset.duration)
try! sloMoVideoTrack.insertTimeRange(assetTimeRange, of: srcVideoTrack, at: .zero)
try! sloMoAudioTrack.insertTimeRange(assetTimeRange, of: srcAudioTrack, at: .zero)
let newDuration = CMTimeMultiplyByFloat64(assetTimeRange.duration, multiplier: 2)
sloMoVideoTrack.scaleTimeRange(assetTimeRange, toDuration: newDuration)
sloMoAudioTrack.scaleTimeRange(assetTimeRange, toDuration: newDuration)
// you can play sloMoComposition in an AVPlayer at this point
// Export to a file using AVAssetExportSession
let exportSession = AVAssetExportSession(asset: sloMoComposition, presetName: AVAssetExportPresetPassthrough)!
exportSession.outputFileType = .mp4
exportSession.outputURL = getDocumentsDirectory().appendingPathComponent("slow-mo-\(Date.timeIntervalSinceReferenceDate).mp4")
exportSession.exportAsynchronously {
    assert(exportSession.status == .completed)
    print("File in \(exportSession.outputURL!)")
}

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赞(0）回复(0）举报 2024-01-05

0kjbasz62#

根据Gordon Child的回答，一旦你有了他所描述的内容，你就可以通过使用this thread中描述的AudioMix基础设施来更改作曲的音高校正策略，因为AVMutableAudioMixInputParameters有一个可设置的AVAudioTimePitchAlgorithm。我证实了这是可行的。

let audioTracks = composition.tracks(withMediaType: .audio) // AVMutableComposition
var trackMixArray = [AVMutableAudioMixInputParameters]()
for audioTrack in audioTracks {
    var trackMix = AVMutableAudioMixInputParameters(track: audioTrack)
    trackMix.audioTimePitchAlgorithm = .varispeed
    trackMix.setVolume(volume, at: .zero)
}
trackMixArray.append(trackMix)
let audioMix = AVMutableAudioMix()
audioMix.inputParameters = trackMixArray
export.audioMix = audioMix // AVAssetExportSession