读取WAV文件并将其转换为Swift中的振幅数组

Question

我在udacity.com上关注了一个非常好的教程,用Swift探索音频应用程序的基础.我想扩展其当前的功能,从显示WAV文件的波形开始.为此,我需要从WAV文件中检索幅度与样本.考虑到我已经录制了文件,我怎么能快速进行？

谢谢!

Answer 1

AudioToolBox 满足你的需要。

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您可以使用AudioFileService从音频文件中获取音频样本，例如文件WAV，

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然后你就可以得到每个样本的幅度。

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 // this is your desired amplitude data\n public internal(set) var packetsX = [Data]()\n\n public required init(src path: URL) throws {\n        Utility.check(error:  AudioFileOpenURL(path as CFURL, .readPermission, 0,  &playbackFile) ,                // set on output to the AudioFileID\n                      operation: "AudioFileOpenURL failed")\n        \n        guard let file = playbackFile else {\n            return\n        }\n        \n        var numPacketsToRead: UInt32 = 0\n        \n        \n        GetPropertyValue(val: &numPacketsToRead, file: file, prop: kAudioFilePropertyAudioDataPacketCount)\n        \n        var asbdFormat = AudioStreamBasicDescription()\n        GetPropertyValue(val: &asbdFormat, file: file, prop: kAudioFilePropertyDataFormat)\n        \n        dataFormatD = AVAudioFormat(streamDescription: &asbdFormat)\n        /// At this point we should definitely have a data format\n        var bytesRead: UInt32 = 0\n        GetPropertyValue(val: &bytesRead, file: file, prop: kAudioFilePropertyAudioDataByteCount)\n        \n        \n        \n        \n        guard let dataFormat = dataFormatD else {\n            return\n        }\n        \n    \n        let format = dataFormat.streamDescription.pointee\n        let bytesPerPacket = Int(format.mBytesPerPacket)\n        \n        for i in 0 ..< Int(numPacketsToRead) {\n            \n            var packetSize = UInt32(bytesPerPacket)\n                \n            let packetStart = Int64(i * bytesPerPacket)\n            let dataPt: UnsafeMutableRawPointer = malloc(MemoryLayout<UInt8>.size * bytesPerPacket)\n            AudioFileReadBytes(file, false, packetStart, &packetSize, dataPt)\n            let startPt = dataPt.bindMemory(to: UInt8.self, capacity: bytesPerPacket)\n            let buffer = UnsafeBufferPointer(start: startPt, count: bytesPerPacket)\n            let array = Array(buffer)\n            packetsX.append(Data(array))\n        }\n        \n        \n        \n    }\n

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例如，该WAV文件的通道一 \xe3\x80\x81 位深度为 Int16。

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// buffer is of two Int8, to express an Int16\nlet buffer = UnsafeBufferPointer(start: startPt, count: bytesPerPacket)\n\n

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更多信息，你可以查看我的github repo

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