AVAssetWriterInput - iphone

Question

I am trying to take the camera input and write the data to disk using avassetwriter. From the delegate, it simply appears that avassetwriterinputpixelbufferadator is failing to append data. I'm not sure why
- (NSURL*) assetURL{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
NSString *filePath = [basePath stringByAppendingPathComponent:#"videoOutput"];
return [NSURL fileURLWithPath:filePath];
}
- (id) init {
if(![super init]) return nil;
self.captureSession = [[c alloc] init];
self.captureSession.sessionPreset = AVCaptureSessionPresetHigh;
// HIGH: 640 x 480
// MEDIUM: 360 x 480
// LOW: 192 x 144
[self loadVideoInput];
[self loadVideoOutput];
[self loadPreviewLayer];
[self loadWriter];
return self;
}
- (void) loadVideoInput{
AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
for (AVCaptureDevice *device in devices) {
if (device.position == AVCaptureDevicePositionFront) {
videoDevice = device;
break;
}
}
if ( videoDevice ) {
NSError *error;
AVCaptureDeviceInput *videoIn = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
if ( !error ) {
if ([self.captureSession canAddInput:videoIn])
[self.captureSession addInput:videoIn];
else NSLog(#"Couldn't add video input");
} else NSLog(#"Couldn't create video input");
} else NSLog(#"Couldn't create video capture device");
}
- (void) loadVideoOutput{
AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
output.alwaysDiscardsLateVideoFrames = YES;
[output setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
//dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
//[output setSampleBufferDelegate:self queue:queue];
//dispatch_release(queue);
//output.minFrameDuration = CMTimeMake(15, 1); // If you wish to cap the frame rate to a known value, such as 15 fps, set
[output setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]]; // BGRA is necessary for manual preview
if ([self.captureSession canAddOutput:videoOut])
[self.captureSession addOutput:videoOut];
else
NSLog(#"Couldn't add video output");
//[self.captureSession addOutput:output];
[output release];
}
- (void) loadPreviewLayer{
previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.captureSession];
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
}
- (void) loadWriter{
NSError *error = nil;
videoWriter = [[AVAssetWriter alloc] initWithURL:[self assetURL] fileType:AVFileTypeQuickTimeMovie error:&error];
NSParameterAssert(videoWriter);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:640], AVVideoWidthKey,
[NSNumber numberWithInt:480], AVVideoHeightKey,
nil];
writerInput = [[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings] retain];
writerInput.expectsMediaDataInRealTime = YES;
NSParameterAssert(writerInput);
NSParameterAssert([videoWriter canAddInput:writerInput]);
[videoWriter addInput:writerInput];
currentTime = kCMTimeZero;
adaptor = [[AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput sourcePixelBufferAttributes:nil] retain];
NSLog(#"Error? %#",error);
}
- (void) captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
if(recording){
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
currentTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
// STUFF ISN'T WORKING HERE
BOOL success = [adaptor appendPixelBuffer:imageBuffer withPresentationTime:currentTime];
NSLog(#"%#",success ? #"YES" : #"NO");
}
}
- (void) startRecording{
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:currentTime];
recording = YES;
}
- (void) stopRecording{
recording = NO;
[writerInput markAsFinished];
[videoWriter endSessionAtSourceTime:currentTime];
[videoWriter finishWriting];
}

Answer 1

You need to remove the existing file ("filePath" in your case) each time, trying to record the video.

Answer 2

[adaptor appendPixelBuffer:imageBuffer withPresentationTime:currentTime];
maybe you need manager the video time by yourself, you get currentTime from sampleBuffer, it's not exactly the video time. try to accumulate the capture time pre frame