录制时裁剪音频文件的方法?
A way to crop AudioFile while recording?
我正在编写一个先进先出的录音应用程序,它使用 AudioQueue
缓冲最多 2.5 分钟的音频。我已经弄明白了大部分,但我在尝试裁剪音频数据时遇到了障碍。
我见过有人用 AVAssetExportSession
这样做,但每次调用 AudioQueueInputCallback
时导出新曲目似乎性能不佳。
如果有人有更好的主意,我不会以任何方式使用 AVAssestExportSession
。
这是我正在写的地方,希望能执行裁剪。
var beforeSeconds = TimeInterval() // find the current estimated duration (not reliable)
var propertySize = UInt32(MemoryLayout.size(ofValue: beforeSeconds))
var osStatus = AudioFileGetProperty(audioRecorder.recordFile!, kAudioFilePropertyEstimatedDuration, &propertySize, &beforeSeconds)
if numPackets > 0 {
AudioFileWritePackets(audioRecorder.recordFile!, // write to disk
false,
buffer.mAudioDataByteSize,
packetDescriptions,
audioRecorder.recordPacket,
&numPackets,
buffer.mAudioData)
audioRecorder.recordPacket += Int64(numPackets) // up the packet index
var afterSeconds = TimeInterval() // find the after write estimated duration (not reliable)
var propertySize = UInt32(MemoryLayout.size(ofValue: afterSeconds))
var osStatus = AudioFileGetProperty(audioRecorder.recordFile!, kAudioFilePropertyEstimatedDuration, &propertySize, &afterSeconds)
assert(osStatus == noErr, "couldn't get record time")
if afterSeconds >= 150.0 {
print("hit max buffer!")
audioRecorder.onBufferMax?(afterSeconds - beforeSeconds)
}
}
这里是执行回调的地方
func onBufferMax(_ difference: Double){
let asset = AVAsset(url: tempFilePath)
let duration = CMTimeGetSeconds(asset.duration)
guard duration >= 150.0 else { return }
guard let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetAppleM4A) else {
print("exporter init failed")
return }
exporter.outputURL = getDocumentsDirectory().appendingPathComponent("buffered.caf") // helper function that calls the FileManager
exporter.outputFileType = AVFileTypeAppleM4A
let startTime = CMTimeMake(Int64(difference), 1)
let endTime = CMTimeMake(Int64(WYNDRConstants.maxTimeInterval + difference), 1)
exporter.timeRange = CMTimeRangeFromTimeToTime(startTime, endTime)
exporter.exportAsynchronously(completionHandler: {
switch exporter.status {
case .failed:
print("failed to export")
case .cancelled:
print("canceled export")
default:
print("export successful")
}
})
}
环形缓冲区是一种有用的结构,可用于在内存或磁盘上存储最近 n 秒的音频。这是一个将音频存储在内存中的简单解决方案,以传统的 UIViewController
格式呈现。
N.B 2.5 分钟的 44.1kHz 音频存储为浮点数需要大约 26MB 的 RAM,这对于移动设备来说太重了。
import AVFoundation
class ViewController: UIViewController {
let engine = AVAudioEngine()
var requiredSamples: AVAudioFrameCount = 0
var ringBuffer: [AVAudioPCMBuffer] = []
var ringBufferSizeInSamples: AVAudioFrameCount = 0
func startRecording() {
let input = engine.inputNode!
let bus = 0
let inputFormat = input.inputFormat(forBus: bus)
requiredSamples = AVAudioFrameCount(inputFormat.sampleRate * 2.5 * 60)
input.installTap(onBus: bus, bufferSize: 512, format: inputFormat) { (buffer, time) -> Void in
self.appendAudioBuffer(buffer)
}
try! engine.start()
}
func appendAudioBuffer(_ buffer: AVAudioPCMBuffer) {
ringBuffer.append(buffer)
ringBufferSizeInSamples += buffer.frameLength
// throw away old buffers if ring buffer gets too large
if let firstBuffer = ringBuffer.first {
if ringBufferSizeInSamples - firstBuffer.frameLength >= requiredSamples {
ringBuffer.remove(at: 0)
ringBufferSizeInSamples -= firstBuffer.frameLength
}
}
}
func stopRecording() {
engine.stop()
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("foo.m4a")
let settings: [String : Any] = [AVFormatIDKey: Int(kAudioFormatMPEG4AAC)]
// write ring buffer to file.
let file = try! AVAudioFile(forWriting: url, settings: settings)
for buffer in ringBuffer {
try! file.write(from: buffer)
}
}
override func viewDidLoad() {
super.viewDidLoad()
// example usage
startRecording()
DispatchQueue.main.asyncAfter(deadline: .now() + 4*60) {
print("stopping")
self.stopRecording()
}
}
}
我正在编写一个先进先出的录音应用程序,它使用 AudioQueue
缓冲最多 2.5 分钟的音频。我已经弄明白了大部分,但我在尝试裁剪音频数据时遇到了障碍。
我见过有人用 AVAssetExportSession
这样做,但每次调用 AudioQueueInputCallback
时导出新曲目似乎性能不佳。
如果有人有更好的主意,我不会以任何方式使用 AVAssestExportSession
。
这是我正在写的地方,希望能执行裁剪。
var beforeSeconds = TimeInterval() // find the current estimated duration (not reliable)
var propertySize = UInt32(MemoryLayout.size(ofValue: beforeSeconds))
var osStatus = AudioFileGetProperty(audioRecorder.recordFile!, kAudioFilePropertyEstimatedDuration, &propertySize, &beforeSeconds)
if numPackets > 0 {
AudioFileWritePackets(audioRecorder.recordFile!, // write to disk
false,
buffer.mAudioDataByteSize,
packetDescriptions,
audioRecorder.recordPacket,
&numPackets,
buffer.mAudioData)
audioRecorder.recordPacket += Int64(numPackets) // up the packet index
var afterSeconds = TimeInterval() // find the after write estimated duration (not reliable)
var propertySize = UInt32(MemoryLayout.size(ofValue: afterSeconds))
var osStatus = AudioFileGetProperty(audioRecorder.recordFile!, kAudioFilePropertyEstimatedDuration, &propertySize, &afterSeconds)
assert(osStatus == noErr, "couldn't get record time")
if afterSeconds >= 150.0 {
print("hit max buffer!")
audioRecorder.onBufferMax?(afterSeconds - beforeSeconds)
}
}
这里是执行回调的地方
func onBufferMax(_ difference: Double){
let asset = AVAsset(url: tempFilePath)
let duration = CMTimeGetSeconds(asset.duration)
guard duration >= 150.0 else { return }
guard let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetAppleM4A) else {
print("exporter init failed")
return }
exporter.outputURL = getDocumentsDirectory().appendingPathComponent("buffered.caf") // helper function that calls the FileManager
exporter.outputFileType = AVFileTypeAppleM4A
let startTime = CMTimeMake(Int64(difference), 1)
let endTime = CMTimeMake(Int64(WYNDRConstants.maxTimeInterval + difference), 1)
exporter.timeRange = CMTimeRangeFromTimeToTime(startTime, endTime)
exporter.exportAsynchronously(completionHandler: {
switch exporter.status {
case .failed:
print("failed to export")
case .cancelled:
print("canceled export")
default:
print("export successful")
}
})
}
环形缓冲区是一种有用的结构,可用于在内存或磁盘上存储最近 n 秒的音频。这是一个将音频存储在内存中的简单解决方案,以传统的 UIViewController
格式呈现。
N.B 2.5 分钟的 44.1kHz 音频存储为浮点数需要大约 26MB 的 RAM,这对于移动设备来说太重了。
import AVFoundation
class ViewController: UIViewController {
let engine = AVAudioEngine()
var requiredSamples: AVAudioFrameCount = 0
var ringBuffer: [AVAudioPCMBuffer] = []
var ringBufferSizeInSamples: AVAudioFrameCount = 0
func startRecording() {
let input = engine.inputNode!
let bus = 0
let inputFormat = input.inputFormat(forBus: bus)
requiredSamples = AVAudioFrameCount(inputFormat.sampleRate * 2.5 * 60)
input.installTap(onBus: bus, bufferSize: 512, format: inputFormat) { (buffer, time) -> Void in
self.appendAudioBuffer(buffer)
}
try! engine.start()
}
func appendAudioBuffer(_ buffer: AVAudioPCMBuffer) {
ringBuffer.append(buffer)
ringBufferSizeInSamples += buffer.frameLength
// throw away old buffers if ring buffer gets too large
if let firstBuffer = ringBuffer.first {
if ringBufferSizeInSamples - firstBuffer.frameLength >= requiredSamples {
ringBuffer.remove(at: 0)
ringBufferSizeInSamples -= firstBuffer.frameLength
}
}
}
func stopRecording() {
engine.stop()
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("foo.m4a")
let settings: [String : Any] = [AVFormatIDKey: Int(kAudioFormatMPEG4AAC)]
// write ring buffer to file.
let file = try! AVAudioFile(forWriting: url, settings: settings)
for buffer in ringBuffer {
try! file.write(from: buffer)
}
}
override func viewDidLoad() {
super.viewDidLoad()
// example usage
startRecording()
DispatchQueue.main.asyncAfter(deadline: .now() + 4*60) {
print("stopping")
self.stopRecording()
}
}
}