HaishinKit，适用于 iOS、macOS、tvOS、visionOS 和 Android。

let mixer = MediaMixer()
let stream0 = RTMPStream() // for Y Service.
let stream1 = RTMPStream() // for F Service.

let view = MTHKView()
view.track = 0 // Video Track Number 0 or 1, UInt8.max.

mixer.addOutput(stream0)
mixer.addOutput(stream1)
mixer.addOutput(view)

let view2 = MTHKView()
stream0.addOutput(view2)

import AVFoundation

let session = AVAudioSession.sharedInstance()
do {
    try session.setCategory(.playAndRecord, mode: .default, options: [.defaultToSpeaker, .allowBluetooth])
    try session.setActive(true)
} catch {
    print(error)
}

let mixer = MediaMixer()

await mixer.setFrameRate(30)
await mixer.setSessionPreset(AVCaptureSession.Preset.medium)

// Do not call beginConfiguration() and commitConfiguration() internally within the scope of the method, as they are called internally.
await mixer.configuration { session in
  session.automaticallyConfiguresApplicationAudioSession = true
}

let front = AVCaptureDevice.default(for: .audio)

try? await mixer.attachAudio(front, track: 0) { audioDeviceUnit in }

await mixer.setMultiTrackAudioMixingEnabled(true)

// Setting the value to 0 will be the same as the value specified in mainTrack.
var settings = AudioMixerSettings(
  sampleRate: Float64 = 44100,
  channels: UInt32 = 0,
)
settings.tracks = [
  0: .init(
    isMuted: Bool = false,
    downmix: Bool = true,
    channelMap: [Int]? = nil
  )
]

async mixer.setAudioMixerSettings(settings)

var audioSettings = AudioCodecSettings()
/// Specifies the bitRate of audio output.
audioSettings.bitrate = 64 * 1000
/// Specifies the mixes the channels or not. Currently, it supports input sources with 4, 5, 6, and 8 channels.
audioSettings.downmix = true
/// Specifies the map of the output to input channels.
audioSettings.channelMap: [Int]? = nil

await stream.setAudioSettings(audioSettings)

let front = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .front)
do {
  try await mixer.attachCamera(front, track: 0) { videoUnit in
    videoUnit.isVideoMirrored = true
    videoUnit.preferredVideoStabilizationMode = .standard
    videoUnit.colorFormat = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
  }
} catch {
  print(error)
}

var videoMixerSettings = VideoMixerSettings()
/// Specifies the image rendering mode.
videoMixerSettings.mode = .passthrough or .offscreen
/// Specifies the muted indicies whether freeze video signal or not.
videoMixerSettings.isMuted = false
/// Specifies the main track number.
videoMixerSettings.mainTrack = 0

await mixer.setVideoMixerSettings(videoMixerSettings)

var videoSettings = VideoCodecSettings(
  videoSize: .init(width: 854, height: 480),
  profileLevel: kVTProfileLevel_H264_Baseline_3_1 as String,
  bitRate: 640 * 1000,
  maxKeyFrameIntervalDuration: 2,
  scalingMode: .trim,
  bitRateMode: .average,
  allowFrameReordering: nil,
  isHardwareEncoderEnabled: true
)

await stream.setVideoSettings(videoSettings)

// Specifies the recording settings. 0" means the same of input.
let recorder = HKStreamRecorder()
stream.addOutput(recorder)

try await recorder.startRecording(fileName, settings: [
  AVMediaType.audio: [
    AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
    AVSampleRateKey: 0,
    AVNumberOfChannelsKey: 0,
    // AVEncoderBitRateKey: 128000,
  ],
  AVMediaType.video: [
    AVVideoCodecKey: AVVideoCodecH264,
    AVVideoHeightKey: 0,
    AVVideoWidthKey: 0,
    /*
    AVVideoCompressionPropertiesKey: [
      AVVideoMaxKeyFrameIntervalDurationKey: 2,
      AVVideoProfileLevelKey: AVVideoProfileLevelH264Baseline30,
      AVVideoAverageBitRateKey: 512000
    ]
    */
  ]
])

try await recorder.stopRecording()