ReplayKit saving video fails first try with mic

Scenario 1:

1. Fire up AVAssetWriter with Audio / Video writer input.
2. Use RPScreenRecorder to start recording with no microphone and process the sample buffers.
3. File writes out fine to Photos on first try.

Scenario 2:

1. Fire up AVAssetWriter with Audio / Video writer input.
2. Use RPScreenRecorder to start recording with microphone enabled and process the sample buffers.

3. File writes fails to write out on the first try.

   UserInfo={NSLocalizedRecoverySuggestion=Try saving again., NSLocalizedDescription=Cannot Save, NSUnderlyingError=0x1c464f3c0 {Error Domain=NSOSStatusErrorDomain Code=-12412 "(null)"}} 2017-10-26 23:25:16.896673-0400 [2135:771655] Status FAILS!: 3 Error Domain=AVFoundationErrorDomain Code=-11823 "Cannot Save"

2nd try works fine.

What am I doing wrong?

Added retry logic to circumvent the issue. Not the greatest solution but it works.

[self.screenRecorder startCaptureWithHandler:^(CMSampleBufferRef  _Nonnull sampleBuffer, RPSampleBufferType bufferType, NSError * _Nullable error) {
        if(CMSampleBufferDataIsReady(sampleBuffer) == false || self.assetWriter == nil)
        {
            return;
        }

        if (self.assetWriter.status == AVAssetWriterStatusFailed) {
            NSLog(@"AVWriter Failed!");
            return;
        }

        if (CMSampleBufferDataIsReady(sampleBuffer)) {
            if(self.assetWriter.status == AVAssetWriterStatusWriting) {
                if (bufferType == RPSampleBufferTypeVideo) {
                    if (!self.startedSession) {

                        dispatch_async(dispatch_get_main_queue(), ^{
                            _startDate = [NSDate date];
                            _recordingTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateRecordingTime) userInfo:nil repeats:YES];

                            // Disable the idle timer while recording
                            [UIApplication sharedApplication].idleTimerDisabled = YES;
                        });

                        CMTime pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
                        [self.assetWriter startSessionAtSourceTime:pts];
                        self.startedSession = YES;
                        NSLog(@"MP4Writer: started session in appendVideoSample");
                    }

                    if (CMTimeCompare(kCMTimeInvalid, self.firstVideoFrameTime) == 0) {
                        self.firstVideoFrameTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
                    }

                    if (self.assetWriterVideoInput.readyForMoreMediaData) {
                        @try {
                            [self.assetWriterVideoInput appendSampleBuffer:sampleBuffer];
                        }
                        @catch(NSException *expection) {
                            NSLog(@"Missed Video Buffer: %@", self.assetWriter.error);
                        }
                    }
                }                

                if (bufferType == RPSampleBufferTypeAudioMic) {
                    if (CMTimeCompare(kCMTimeInvalid, self.firstVideoFrameTime) == 0 ||
                        CMTimeCompare(self.firstVideoFrameTime, CMSampleBufferGetPresentationTimeStamp(sampleBuffer)) == 1) {
                        return;
                    }

                    if (!self.startedSession) {
                        CMTime pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
                        [self.assetWriter startSessionAtSourceTime:pts];
                        self.startedSession = YES;
                        NSLog(@"MP4Writer: started session in appendAudioSample");
                    }

                    if (self.assetWriterAudioInput.isReadyForMoreMediaData) {
                        @try {
                            [self.assetWriterAudioInput appendSampleBuffer:sampleBuffer];
                        }
                        @catch(NSException *expection) {
                            NSLog(@"Missed Audio Buffer: %@", self.assetWriter.error);
                        }
                    }
                }
            }

        }
    } completionHandler:^(NSError * _Nullable error) {
        if (!error) {
            NSLog(@"Recording started successfully.");
        }
    }];