在重新录制的实际视频之前，出现黑屏

Question

我正在我的应用程序中录制视频，其录制时间由服务器发送。服务器测试视频中的某些手势，如果失败，则会发回一个标志，要求重新记录并重新发送。

问题：初始视频时长正确。但是在服务器“重试请求”的情况下，视频会附加黑屏一定时间，然后播放录制的视频。

流程：

- (void)viewDidLoad {
    [super viewDidLoad];
    // get recording time
    [self getRecordingData];
}

录音功能：

-(void)startRecording {
    self.isRecording = YES;
    self.isProcessing = YES;
    [self startWritingToVideoFile];
    [self logicMethodToStopRecording];
}

写入视频文件功能

-(void)startWritingToVideoFile{
    NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSNumber numberWithInt:640], AVVideoWidthKey, [NSNumber numberWithInt:480], AVVideoHeightKey, AVVideoCodecTypeH264, AVVideoCodecKey,nil];
    self.assetWriterInput = [AVAssetWriterInput  assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings];
    [self.assetWriterInput setTransform: CGAffineTransformMakeRotation( ( 90 * M_PI ) / 180 )];
    self.pixelBufferAdaptor =
    [[AVAssetWriterInputPixelBufferAdaptor alloc]
     initWithAssetWriterInput:self.assetWriterInput
     sourcePixelBufferAttributes:
     [NSDictionary dictionaryWithObjectsAndKeys:
      [NSNumber numberWithInt:kCVPixelFormatType_32BGRA],
      kCVPixelBufferPixelFormatTypeKey,
      nil]];
    
    self.videoPath = [Utilities pathForTemporaryFileWithSuffix:@"mov"];
    NSURL *videoURL = [NSURL fileURLWithPath:self.videoPath];
    /* Asset writer with MPEG4 format*/
    self.assetWriterMyData = [[AVAssetWriter alloc]
                              initWithURL: videoURL
                              fileType:AVFileTypeMPEG4
                              error:nil];
    [self.assetWriterMyData addInput:self.assetWriterInput];
    self.assetWriterInput.expectsMediaDataInRealTime = YES;
    [self.assetWriterMyData startWriting];
    [self.assetWriterMyData startSessionAtSourceTime:kCMTimeZero];
    self.isReadyToWrite = YES;
}

停止记录的逻辑方法：

-(void)logicMethodToStopRecording{
    
    float time = [self.timeFromServer floatValue];
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, time * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        [self stopRecording];
    });
}

实际停止记录方法：

-(void)stopRecording{
    [self stopWritingToVideoFile];
}

-(void)stopWritingToVideoFile {
    [self.assetWriterMyData finishWritingWithCompletionHandler:^{
        [self showLoading];
        if(!self.continueRunning){
            return;
        }
         [self sendVideo]; 
// sends video file referenced in startWritingToVideoFile method
        }];
    }

发送视频的方法：

-(void)sendVideo{
    [self.xxxxxx sendAPI:self.userToVerifyUserId videoPath:self.videoPath callback:^(NSString *jsonResponse){
        [self handleResponse:jsonResponse];
    }];
}

通过以下方法处理响应：

-(void)handleResponse: (NSString*)result{
    
    [Utilities deleteFile:self.videoPath];
        
   //if no success but retry is true. re-record and re-send.
    if(!self.success && retry){
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 3.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
            [self startRecording]; // start recording called again
        });
    }

我创建的初始文件假设有 x秒的视频----它正在正确生成

但是，在重新尝试期间：

我要删除旧文件并重新创建新文件。在第二次和第三次尝试中，我的视频输出仍然黑屏了 n + x和2n + x 次。请帮忙。

**************编辑************************************ ********************

另外，AVCaptureSession的回调方法执行以下操作：

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection {
    
        CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
        // a very dense way to keep track of the time at which this frame
        // occurs relative to the output stream, but it's just an example!
        static int64_t frameNumber = 0;
        if(self.assetWriterInput.readyForMoreMediaData){
            if(self.pixelBufferAdaptor != nil){
                [self.pixelBufferAdaptor appendPixelBuffer:imageBuffer
                                      withPresentationTime:CMTimeMake(frameNumber, 25)];
                frameNumber++;
            }
        }
    }
}

**************************编辑-2 ****************** **************************** p

+(NSString *)pathForTemporaryFileWithSuffix:(NSString *)suffix
{
    NSString *  result;
    CFUUIDRef   uuid;
    CFStringRef uuidStr;
    
    uuid = CFUUIDCreate(NULL);
    assert(uuid != NULL);
    
    uuidStr = CFUUIDCreateString(NULL, uuid);
    assert(uuidStr != NULL);
    
    result = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", uuidStr, suffix]];
    assert(result != nil);
    
    CFRelease(uuidStr);
    CFRelease(uuid);
    
    return result;
}