How to recover and continue recording after mid-stream AVAssetWriter failure?

[dawilster]

Question

When AVAssetWriter enters .failed state mid-recording with HaishinKit.StreamRecorder.Error error 5., what is the correct way to recover and resume recording with StreamRecorder?

After the failure we observe:

1. The error AsyncStream yields failedToAppend continuously.
2. isRecording remains true.
3. stopRecording() throws failedToFinishWriting because writer.status is no longer .writing.

Specific questions:

1. After AVAssetWriter enters .failed state, should we call stopRecording() at all, or just abandon the recorder instance?
2. Is creating a new StreamRecorder and re-attaching via stream.addOutput() the intended way to resume?
3. Does the old recorder need to be explicitly removed from the stream first via stream.removeOutput()?

Background / Tried Steps

We use StreamRecorder to record locally via MediaMixer → RTMPStream → StreamRecorder (when streaming) or MediaMixer → StreamRecorder (record-only mode), with movieFragmentInterval set to 60 seconds.

This is the exception we see consistently via the error AsyncStream when the writer fails mid-recording (failedToAppend):

HaishinKit.StreamRecorder.Error error 5 (failedToAppend)

writer.error:
  Error Domain=NSURLErrorDomain Code=-3000 "Cannot create file"
    NSUnderlyingError: NSOSStatusErrorDomain Code=-12143

After this initial failure, failedToAppend continues to yield on every subsequent sample buffer, and calling stopRecording() throws failedToFinishWriting because the writer is no longer in .writing state.

Our setup:

let recorder = StreamRecorder()
let mixer = MediaMixer()
let stream = RTMPStream()

mixer.addOutput(stream)
stream.addOutput(recorder)
await recorder.setMovieFragmentInterval(60.0)

try await recorder.startRecording(
    documentsDirectory.appendingPathComponent("recording.mov"),
    settings: [
        AVMediaType.audio: [
            AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
            AVSampleRateKey: 48000.0,
            AVNumberOfChannelsKey: 1,
        ],
        AVMediaType.video: [
            AVVideoCodecKey: AVVideoCodecType.h264,
            AVVideoHeightKey: 1080,
            AVVideoWidthKey: 1920,
        ]
    ]
)

// Error monitoring
Task {
    for await error in recorder.error {
        await recoverRecording()
    }
}

Our current recovery attempt:

func recoverRecording() async {
    // Is this necessary? It throws failedToFinishWriting.
    _ = try? await recorder.stopRecording()

    // Create fresh instance — is this the right approach?
    recorder = StreamRecorder()
    await recorder.setMovieFragmentInterval(60.0)

    // Re-attach — do we need to remove the old recorder first?
    await stream.addOutput(recorder)

    // Start new recording with a new file URL
    try? await recorder.startRecording(newOutputURL, settings: [...])
}

Context: We build a live streaming app for recording funeral and memorial services. Our users are non-technical, typically funeral home staff operating an iPad/iPhone on a tripod. When a recording fails silently, the family's once-in-a-lifetime event is lost. What we're struggling with is reliably resuming recording after the failure so we capture the rest of the service.

And just signed up as a sponsor, so any guidance on the intended recovery pattern would be much appreciated.

Environment

• HaishinKit: 2.2.3
• Devices: Observed across 14+ models — iPads (7th–10th gen, Air 3–4, Pro 4, Mini 6) and iPhones (13, 15 Pro, 15 Pro Max)
• OS Versions: iOS 15.5 through 26.2 (most frequent on 18.x)
• Recording format: .mov with movieFragmentInterval(60.0)

[shogo4405]

The following changes are required:

• The Task must be cancelled; otherwise, it will reference an old recorder instance and will not behave as expected.

// Error monitoring
errorTask = Task {
    for await error in recorder.error {
        await recoverRecording()
    }
}


func recoverRecording() async {
     // Is this necessary? It throws failedToFinishWriting.
     _ = try? await recorder.stopRecording()

    stream.removeOutout(recorder)

    // You must cancel error handler.
    errorTask?.cancel()

    // Create fresh instance — is this the right approach?
    recorder = StreamRecorder()
    await recorder.setMovieFragmentInterval(60.0)

    // Re-attach — do we need to remove the old recorder first?
    await stream.addOutput(recorder)

    // Start new recording with a new file URL
    try? await recorder.startRecording(newOutputURL, settings: [...])

    // Re-attach errorTask
   errorTask = Task {
     for await error in recorder.error {
       await recoverRecording()
     }
   }
}

[shogo4405]

If it fails, it is still necessary to create a StreamRecorder instance.
It would be difficult to restore the current version, so I’m considering fixing it in the next version.