Apple Immersive Video Live Production Tools

import AVFoundation
import VideoToolbox
import CoreMedia

class ImmersiveVideoRecorder {
    private var assetWriter: AVAssetWriter?
    private var videoInput: AVAssetWriterInput?
    private var audioInput: AVAssetWriterInput?

    /// Width and height for a single eye; the codec carries both eyes as dual essences.
    private let eyeWidth = 5760
    private let eyeHeight = 2880
    private let frameRate: Double = 60

    func startRecording(to outputURL: URL) throws {
        let writer = try AVAssetWriter(outputURL: outputURL, fileType: .mov)

        // Video settings: ProRes 4444 for maximum fidelity
        let videoSettings: [String: Any] = [
            AVVideoCodecKey: AVVideoCodecType.proRes4444,
            AVVideoWidthKey: eyeWidth,
            AVVideoHeightKey: eyeHeight,
            AVVideoCompressionPropertiesKey: [
                // Required: marks the MOV with correct Apple Immersive Video
                // stereo projection metadata (vexu box) for ecosystem interoperability.
                kVTProjectionKind_AppleImmersiveVideo as String: true
            ] as [String: Any]
        ]

        let videoInput = AVAssetWriterInput(
            mediaType: .video,
            outputSettings: videoSettings
        )
        // Live sources deliver frames in real time; do not wait for additional frames.
        videoInput.expectsMediaDataInRealTime = true

        guard writer.canAdd(videoInput) else {
            throw RecorderError.cannotAddVideoInput
        }
        writer.add(videoInput)

        // ASAF spatial audio: 64-channel PCM (high-order ambisonics + objects)
        let channelLayout = AudioChannelLayout()
        let audioSettings: [String: Any] = [
            AVFormatIDKey: kAudioFormatLinearPCM,
            AVSampleRateKey: 48000,
            AVNumberOfChannelsKey: 64,
            AVLinearPCMBitDepthKey: 32,
            AVLinearPCMIsFloatKey: true,
            AVLinearPCMIsNonInterleaved: false
        ]

        let audioInput = AVAssetWriterInput(
            mediaType: .audio,
            outputSettings: audioSettings
        )
        audioInput.expectsMediaDataInRealTime = true

        if writer.canAdd(audioInput) {
            writer.add(audioInput)
        }

        self.assetWriter = writer
        self.videoInput = videoInput
        self.audioInput = audioInput

        writer.startWriting()
        writer.startSession(atSourceTime: .zero)
        print("Recording started: \(outputURL.lastPathComponent)")
    }

    /// Call with each ProRes CMSampleBuffer arriving from the 2110-22 live stream.
    /// Because the live payload is already ProRes, frames are copied directly —
    /// no re-encode step, no generational quality loss.
    func appendVideoFrame(_ sampleBuffer: CMSampleBuffer) {
        guard let input = videoInput, input.isReadyForMoreMediaData else { return }
        input.append(sampleBuffer)
    }

    /// Call with each ASAF PCM CMSampleBuffer arriving from the 2110-30 live stream.
    func appendAudioBuffer(_ sampleBuffer: CMSampleBuffer) {
        guard let input = audioInput, input.isReadyForMoreMediaData else { return }
        input.append(sampleBuffer)
    }

    func stopRecording() async {
        videoInput?.markAsFinished()
        audioInput?.markAsFinished()
        await assetWriter?.finishWriting()
        print("Recording finished. Status: \(assetWriter?.status.rawValue ?? -1)")
    }

    enum RecorderError: Error {
        case cannotAddVideoInput
    }
}