How to save recorded video using AVAssetWriter? - ios

Question

I tried many other blogs and stack overflow. I didn't get solution for this, I can able to create custom camera with preview. I need video with custom frame, that's why I am using AVAssetWriter. But i unable to save recorded video into documents. I tried like this,
-(void) initilizeCameraConfigurations {
if(!captureSession) {
captureSession = [[AVCaptureSession alloc] init];
[captureSession beginConfiguration];
captureSession.sessionPreset = AVCaptureSessionPresetHigh;
self.view.backgroundColor = UIColor.blackColor;
CGRect bounds = self.view.bounds;
captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:captureSession];
captureVideoPreviewLayer.backgroundColor = [UIColor clearColor].CGColor;
captureVideoPreviewLayer.bounds = self.view.frame;
captureVideoPreviewLayer.connection.videoOrientation = AVCaptureVideoOrientationPortrait;
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
captureVideoPreviewLayer.position = CGPointMake(CGRectGetMidX(bounds), CGRectGetMidY(bounds));
[self.view.layer addSublayer:captureVideoPreviewLayer];
[self.view bringSubviewToFront:self.controlsBgView];
}
// Add input to session
NSError *err;
videoCaptureDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoCaptureDevice error:&err];
if([captureSession canAddInput:videoCaptureDeviceInput]) {
[captureSession addInput:videoCaptureDeviceInput];
}
docPathUrl = [[NSURL alloc] initFileURLWithPath:[self getDocumentsUrl]];
assetWriter = [AVAssetWriter assetWriterWithURL:docPathUrl fileType:AVFileTypeQuickTimeMovie error:&err];
NSParameterAssert(assetWriter);
//assetWriter.movieFragmentInterval = CMTimeMakeWithSeconds(1.0, 1000);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:300], AVVideoWidthKey,
[NSNumber numberWithInt:300], AVVideoHeightKey,
nil];
writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
writerInput.expectsMediaDataInRealTime = YES;
writerInput.transform = CGAffineTransformMakeRotation(M_PI);
NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], kCVPixelBufferPixelFormatTypeKey,
[NSNumber numberWithInt:300], kCVPixelBufferWidthKey,
[NSNumber numberWithInt:300], kCVPixelBufferHeightKey,
nil];
assetWriterPixelBufferInput = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];
if([assetWriter canAddInput:writerInput]) {
[assetWriter addInput:writerInput];
}
// Set video stabilization mode to preview layer
AVCaptureVideoStabilizationMode stablilizationMode = AVCaptureVideoStabilizationModeCinematic;
if([videoCaptureDevice.activeFormat isVideoStabilizationModeSupported:stablilizationMode]) {
[captureVideoPreviewLayer.connection setPreferredVideoStabilizationMode:stablilizationMode];
}
// image output
stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[stillImageOutput setOutputSettings:outputSettings];
[captureSession addOutput:stillImageOutput];
[captureSession commitConfiguration];
if (![captureVideoPreviewLayer.connection isEnabled]) {
[captureVideoPreviewLayer.connection setEnabled:YES];
}
[captureSession startRunning];
}
-(IBAction)startStopVideoRecording:(id)sender {
if(captureSession) {
if(isVideoRecording) {
[writerInput markAsFinished];
[assetWriter finishWritingWithCompletionHandler:^{
NSLog(#"Finished writing...checking completion status...");
if (assetWriter.status != AVAssetWriterStatusFailed && assetWriter.status == AVAssetWriterStatusCompleted)
{
// Video saved
} else
{
NSLog(#"#123 Video writing failed: %#", assetWriter.error);
}
}];
} else {
[assetWriter startWriting];
[assetWriter startSessionAtSourceTime:kCMTimeZero];
isVideoRecording = YES;
}
}
}
-(NSString *) getDocumentsUrl {
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
docPath = [[docPath stringByAppendingPathComponent:#"Movie"] stringByAppendingString:#".mov"];
if([[NSFileManager defaultManager] fileExistsAtPath:docPath]) {
NSError *err;
[[NSFileManager defaultManager] removeItemAtPath:docPath error:&err];
}
NSLog(#"Movie path : %#",docPath);
return docPath;
}
#end
Correct me if anything wrong. Thank you in advance.

Answer 1

You don't say what actually goes wrong, but two things look wrong with your code:
docPath = [[docPath stringByAppendingPathComponent:#"Movie"] stringByAppendingString:#".mov"];
looks like it creates an undesired path like this #"/path/Movie/.mov", when you want this:
docPath = [docPath stringByAppendingPathComponent:#"Movie.mov"];
And your timeline is wrong. Your asset writer starts at time 0, but the sampleBuffers start at CMSampleBufferGetPresentationTimestamp(sampleBuffer) > 0, so instead do this:
-(void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
if(firstSampleBuffer) {
[assetWriter startSessionAtSourceTime:CMSampleBufferGetPresentationTimestamp(sampleBuffer)];
}
[writerInput appendSampleBuffer:sampleBuffer];
}

Answer 2

Conceptually, you have to main functional areas: One that generates video frames – this the AVCaptureSession, and everything that is attached to it –, and another that writes these frames to a file – in your case the AVAssetWriter with attached inputs.
The problem with your code is: There is no connection between these two. No video frames / images coming out of the capture session are passed to the asset writer inputs.
Furthermore, the AVCaptureStillImageOutput method -captureStillImageAsynchronouslyFromConnection:completionHandler: is nowhere called, so the capture session actually produces no frames.
So, as a minimum, implement something like this:
-(IBAction)captureStillImageAndAppend:(id)sender
{
[stillImageOutput captureStillImageAsynchronouslyFromConnection:stillImageOutput.connections.firstObject completionHandler:
^(CMSampleBufferRef imageDataSampleBuffer, NSError* error)
{
// check error, omitted here
if (CMTIME_IS_INVALID( startTime)) // startTime is an ivar
[assetWriter startSessionAtSourceTime:(startTime = CMSampleBufferGetPresentationTimeStamp( imageDataSampleBuffer))];
[writerInput appendSampleBuffer:imageDataSampleBuffer];
}];
}
Remove the AVAssetWriterInputPixelBufferAdaptor, it's not used.
But there are issues with AVCaptureStillImageOutput:
it's only intended to produce still images, not videos
it must be configured to produce uncompressed sample buffers if the asset writer input is configured to compress the appended sample buffers (stillImageOutput.outputSettings = #{ (NSString*)kCVPixelBufferPixelFormatTypeKey: #(kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)};)
it's deprecated under iOS
If you actually want to produce a video, as opposed to a sequence of still images, instead of the AVCaptureStillImageOutput add a AVCaptureVideoDataOutput to the capture session. It needs a delegate and a serial dispatch queue to output the sample buffers. The delegate has to implement something like this:
-(void)captureOutput:(AVCaptureOutput*)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{
if (CMTIME_IS_INVALID( startTime)) // startTime is an ivar
[assetWriter startSessionAtSourceTime:(startTime = CMSampleBufferGetPresentationTimeStamp( sampleBuffer))];
[writerInput appendSampleBuffer:sampleBuffer];
}
Note that
you will want to make sure that the AVCaptureVideoDataOutput only outputs frames when you're actually recording; add/remove it from the capture session or enable/disable its connection in the startStopVideoRecording action
reset the startTime to kCMTimeInvalid before starting another recording