I'm writing a first in first out recording app that buffers up to 2.5 mins of audio using AudioQueue
. I've got most of it figured out but I'm at a roadblock trying to crop audio data.
I've seen people do it with AVAssetExportSession
but it seems like it wouldn't be performant to export a new track every time the AudioQueueInputCallback
is called.
I'm not married to using AVAssestExportSession
by any means if anyone has a better idea.
Here's where I'm doing my write and was hoping to execute the crop.
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)
}
}
Here's where the callback is executed
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")
}
})
}