我在udacity.com上有一个非常好的教程，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！
答案 0 :(得分：0)
SELECT well.well_name, wellbore.wellbore_name, operation.operation_name, COUNT(*)
FROM well
INNER JOIN wellbore ON wellbore.well_uid = well.well_uid
INNER JOIN operation ON wellbore.well_uid = operation.well_uid
GROUP BY well.well_name,wellbore.wellbore_name
HAVING COUNT(*) > 1
满足您的需求。
您可以使用 AudioToolBox 从音频文件中获取音频样本，例如 AudioFileService 文件，
然后您可以从每个样本中获得幅度。
WAV例如 // this is your desired amplitude data
public internal(set) var packetsX = [Data]()
public required init(src path: URL) throws {
Utility.check(error: AudioFileOpenURL(path as CFURL, .readPermission, 0, &playbackFile) , // set on output to the AudioFileID
operation: "AudioFileOpenURL failed")
guard let file = playbackFile else {
return
}
var numPacketsToRead: UInt32 = 0
GetPropertyValue(val: &numPacketsToRead, file: file, prop: kAudioFilePropertyAudioDataPacketCount)
var asbdFormat = AudioStreamBasicDescription()
GetPropertyValue(val: &asbdFormat, file: file, prop: kAudioFilePropertyDataFormat)
dataFormatD = AVAudioFormat(streamDescription: &asbdFormat)
/// At this point we should definitely have a data format
var bytesRead: UInt32 = 0
GetPropertyValue(val: &bytesRead, file: file, prop: kAudioFilePropertyAudioDataByteCount)
guard let dataFormat = dataFormatD else {
return
}
let format = dataFormat.streamDescription.pointee
let bytesPerPacket = Int(format.mBytesPerPacket)
for i in 0 ..< Int(numPacketsToRead) {
var packetSize = UInt32(bytesPerPacket)
let packetStart = Int64(i * bytesPerPacket)
let dataPt: UnsafeMutableRawPointer = malloc(MemoryLayout<UInt8>.size * bytesPerPacket)
AudioFileReadBytes(file, false, packetStart, &packetSize, dataPt)
let startPt = dataPt.bindMemory(to: UInt8.self, capacity: bytesPerPacket)
let buffer = UnsafeBufferPointer(start: startPt, count: bytesPerPacket)
let array = Array(buffer)
packetsX.append(Data(array))
}
}
文件有通道一、位深为Int16。
WAV更多信息，您可以查看my github repo