I am developing a small wrapper to create a framework on AVFoundation that wraps up some functionality and I want to create tests around it.
I'm calling this only on the initializer of my class implementation as it only needs to be run once. I don't want to add logic specific that avoids this line to be run when I'm running the tests but I am having trouble testing functionality on this class like reading an audio file and appending it to the audio buffer.
private let mixerNode = AVAudioMixerNode()
// Used to get audio from the microphone.
private lazy var audioEngine = AVAudioEngine()
private func configureAudioEngine() {
// Get the native audio format of the engine's input bus.
let inputFormat = audioEngine.inputNode.inputFormat(forBus: 0)
// Set an output format
// let outputFormat = AVAudioFormat(standardFormatWithSampleRate: 48000, channels: 1)
let outputFormat = AVAudioFormat(
standardFormatWithSampleRate: audioEngine.inputNode.outputFormat(forBus: 0).sampleRate,
channels: 1)
// Mixer node converts the input
audioEngine.attach(mixerNode)
// Attach the mixer to the microphone input and the output of the audio engine.
// Crash on the line below, (shown on the lines below with the prints)
audioEngine.connect(audioEngine.inputNode, to: mixerNode, format: inputFormat)
audioEngine.connect(mixerNode, to: audioEngine.outputNode, format: outputFormat)
// Install a tap on the mixer node to capture the microphone audio.
mixerNode.installTap(onBus: 0,
bufferSize: 8192,
format: outputFormat) { [weak self] buffer, audioTime in
// Add captured audio to the buffer
// TODO: Do operation on the buffer data that's being received...
}
}
I am seeing inconsistencies between running this on the device and running the tests as the returned AVAudioFormat is different. These two prints below are from the same line indicated above
AVAudioEngine during a test
Tests iOS-Runner[4515:894511] [aurioc] AURemoteIO.cpp:1123 failed: 561015905 (enable 1, outf< 2 ch, 0 Hz, Float32, deinterleaved> inf< 2 ch, 0 Hz, Float32, deinterleaved>)
AVAudioEngine when running on device
<AVAudioFormat 0x2834962b0: 1 ch, 44100 Hz, Float32>
Related
I have an audio file with 5.1 channels. How do I get access to a buffer containing all of this information during playback?
The setup is roughly like this
engine.attach(playerNode)
engine.connect(playerNode, to: engine.mainMixerNode, format: audioFile.processingFormat)
engine.prepare()
try? engine.start()
File loading and playback is pretty standard, I think.
let audioFile: AVAudioFile = try? .init(forReading: url, commonFormat: AVAudioCommonFormat.pcmFormatFloat32, interleaved: false)
// ...
playerNode.scheduleFile(audioFile, at: nil)
Then I used a tap on the bus to get access to the buffer.
let format: AVAudioFormat = engine.mainMixerNode.outputFormat(forBus: 0)
engine.mainMixerNode.installTap(
onBus: 0,
bufferSize: 1024,
format: format
) { buffer, time in
// Do something cool with buffer, but buffer only has two channels.
for channel in 0..<buffer.format.channelCount {
}
}
Questions:
Is a tap on the the bus the right way to get hold of this data? Os there a better way?
How do I get at the data for more than two channels?
Install your tap on the playerNode and don't bother specifying the format:
playerNode.installTap(
onBus: 0,
bufferSize: 1024,
format: nil
) { buffer, time in
// 6 channel buffer
for channel in 0..<buffer.format.channelCount {
}
}
Is it possible to record audio through the microphone of AirPod Pros at a sample rate higher than 16kHz?
I'm tapping into the microphone bus using audioEngine:
let node = audioEngine.inputNode
let recordingFormat = node.outputFormat(forBus: 0)
node.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { [unowned self] (buffer, _) in
self.request!.append(buffer)
}
audioEngine.prepare()
do {
try audioEngine.start()
} catch {
fatalError("\t[Error] There was a problem starting speech recognition")
}
It seems as though the default sample rate (found in recordingFormat) is 16000Hz, and I've had difficulty specifying a higher sample rate.
This particular sample rate returns an audio recording with fairly low quality compared to a recording from the iPhone microphone, which has a sample rate of 44100Hz.
Try calling the following before starting your AVAudioEngine instance
AVAudioSession.sharedInstance().setCategory(.playAndRecord)
try AVAudioSession.sharedInstance().setPreferredSampleRate(44_100)
Is it possible to select the input device in AVAudioEngine using Swift on macOS?
Use case:
I am using SFSpeechRecognizer on macOS.
To feed microphone data into it I am using
private let audioEngine = AVAudioEngine()
:
let inputNode = audioEngine.inputNode
let recordingFormat = inputNode.outputFormat(forBus: 0)
inputNode.installTap( onBus: 0, bufferSize: 1024, format: recordingFormat )
{ (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
self.recognitionRequest?.append( buffer )
}
audioEngine.prepare()
try audioEngine.start()
This will use the system default microphone.
I have an external USB microphone I wish to use instead. I can go into System Preferences -> Audio and set the default output device to my USB microphone. Then it will work. But if I disconnect the microphone and reconnect it to a different USB port, I will have to go through the process of setting it as default again.
To avoid having to do this repeatedly, I would like to set the microphone manually from code.
Is this possible?
EDIT: I found Set AVAudioEngine Input and Output Devices which uses Obj-C.
So I've been trying to do Speech Recognition in Swift using the builtin SFSpeechRecognition class while also downsampling and then recording the audio to a file, but I'm not well-versed enough in AVAudioEngine to figure it out.
I've gotten the Speech Recognition to work by itself, and I've gotten the recording the audio to work by itself, but I can't get them to work together.
Here's my existing code in which I try to record - the remaining code is just the standard speech recognition type stuff:
let audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 16000, channels: 1, interleaved: false)
let mixer = AVAudioMixerNode()
audioEngine.attach(mixer)
audioEngine.connect(inputNode!, to: mixer, format: inputNode!.inputFormat(forBus: 0))
// 1 Connecting Mixer
audioEngine.connect(mixer, to: audioEngine.outputNode, format: audioFormat)
// 2 Recognition
inputNode!.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
print("Testing if this tap works")
self.recognitionRequest?.append(buffer)
}
// 3 Downsampling and recording
mixer.installTap(onBus: 0, bufferSize: 1024, format: audioFormat){ (buffer, when) in
print(buffer)
try? self.outputFile!.write(from: buffer)
}
If I comment out 3, then the speech recognition works, but otherwise 2 doesn't even run - the tap doesn't output anything. I also can't put the recognitionRequest in 3 because then the speech recognition throws an error. I see in the docs that each bus can only have one tap - how can I get around this? Should I use an AVConnectionPoint? I don't see it well documented in the docs.
I am working on a push to talk functionality where sender can send an audio in form of bytes array to server and receiver can listen it at realtime through socket connection.
when i try to play video at receiver end using AVAudioEngine, it's not working.
let buffer = dataToPCMBuffer(format: format16KHzMono!, data: data)
let player = AVAudioPlayerNode()
self.audioEngine?.attach(audioPlayerNode)
let mixer = self.audioEngine?.mainMixerNode
self.audioEngine?.connect(player, to: mixer!, format: AVAudioFormat.init(commonFormat: AVAudioCommonFormat.pcmFormatInt16, sampleRate: 16000, channels: 1, interleaved: true) )
self.playerQueue.async {
self.audioPlayerNode.scheduleBuffer(buffer!) {
print("stopping")
if self.audioEngine!.isRunning {
self.audioPlayerNode.play()
}else {
try? self.audioEngine?.start()
}
}
And, i am facing crash at below given line.
self.audioEngine?.connect(player, to: mixer!, format: AVAudioFormat.init(commonFormat: AVAudioCommonFormat.pcmFormatInt16, sampleRate: 16000, channels: 1, interleaved: true) )
Any help will be appreciated.
I think it’s the format in your connection. Try using nil instead. There are some magic numbers needed for sample rates, maybe 16000 is not one of them.