I am unable to save an AVFoundation video to a local url

Question

I'm a new to programming and Objective-C (~6 weeks) and now I'm working with AVFoundation for the first time. My goal is a stretch for my level, but shouldn't be too difficult for someone familiar with the framework.

My goal is to create a 'Snapchat' style custom camera interface that captures a still image when you tap on the button, and records video when you hold it down.

I've been able to piece together and crush through most of the code (video preview, capturing still images, programmatic buttons, etc.), but I'm not able to successfully save the video locally (will add it to a project built on top of Parse later this week).

ViewController.h (reference)

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>

@interface ViewController : UIViewController 

@property UIButton *button;
@property UIButton *saveButton;
@property UIImageView *previewView;

#define VIDEO_FILE @"test.mov"

@end

ViewController.m

The way I've constructed my code is I initialize the session in the first set of methods, and then break apart image and video capture into their own separate sections. The input device is AVMediaTypeVideo and it outputs to AVCaptureStillImageOutput and AVCaptureMovieFileOutput respectively.

    #import "ViewController.h"

@interface ViewController () <AVCaptureFileOutputRecordingDelegate>

@end

@implementation ViewController
AVCaptureSession *session;
AVCaptureStillImageOutput *imageOutput;
AVCaptureMovieFileOutput *movieOutput;
AVCaptureConnection *videoConnection;

- (void)viewDidLoad {
    [super viewDidLoad];
    [self testDevices];
    self.view.backgroundColor = [UIColor blackColor];

    //Image preview
    self.previewView = [[UIImageView alloc]initWithFrame:self.view.frame];
    self.previewView.backgroundColor = [UIColor whiteColor];
    self.previewView.contentMode = UIViewContentModeScaleAspectFill;
    self.previewView.hidden = YES;
    [self.view addSubview:self.previewView];

    //Buttons
    self.button = [self createButtonWithTitle:@"REC" chooseColor:[UIColor redColor]];
    UILongPressGestureRecognizer *longPressRecognizer = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(handleLongPressGesture:)];
    [self.button addGestureRecognizer:longPressRecognizer];
    [self.button addTarget:self action:@selector(captureImage) forControlEvents:UIControlEventTouchUpInside];

    self.saveButton = [self createSaveButton];
    [self.saveButton addTarget:self action:@selector(saveActions) forControlEvents:UIControlEventTouchUpInside];
}

- (void)viewWillAppear:(BOOL)animated {
    //Tests
    [self initializeAVItems];
    NSLog(@"%@", videoConnection);
    NSLog(@"%@", imageOutput.connections);
    NSLog(@"%@", imageOutput.description.debugDescription);
}

#pragma mark - AV initialization

- (void)initializeAVItems {
    //Start session, input
    session = [[AVCaptureSession alloc]init];
    [session setSessionPreset:AVCaptureSessionPresetPhoto];

    AVCaptureDevice *inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    NSError *error;
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&error];
    if ([session canAddInput:deviceInput]) {
        [session addInput:deviceInput];
    } else {
        NSLog(@"%@", error);
    }

    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:session];
    [previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    //Layer preview
    CALayer *viewLayer = [[self view] layer];
    [viewLayer setMasksToBounds:YES];

    CGRect frame = self.view.frame;
    [previewLayer setFrame:frame];
    [viewLayer insertSublayer:previewLayer atIndex:0];

    //Image Output
    imageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *imageOutputSettings = [[NSDictionary alloc]initWithObjectsAndKeys:AVVideoCodecJPEG, AVVideoCodecKey, nil];
    imageOutput.outputSettings = imageOutputSettings;

    //Video Output
    movieOutput = [[AVCaptureMovieFileOutput alloc] init];


    [session addOutput:movieOutput];
    [session addOutput:imageOutput];
    [session startRunning];
}

- (void)testDevices {
    NSArray *devices = [AVCaptureDevice devices];
    for (AVCaptureDevice *device in devices) {
        NSLog(@"Device name: %@", [device localizedName]);
        if ([device hasMediaType:AVMediaTypeVideo]) {
            if ([device position] == AVCaptureDevicePositionBack) {
                NSLog(@"Device position : back");
            }
            else {
                NSLog(@"Device position : front");
            }
        }
    }
}

#pragma mark - Image capture

- (void)captureImage {
    AVCaptureConnection *videoConnection = nil;
    for (AVCaptureConnection *connection in imageOutput.connections) {
        for (AVCaptureInputPort *port in [connection inputPorts]) {
            if ([[port mediaType] isEqual:AVMediaTypeVideo]) {
                videoConnection = connection;
                break;
            }
        }
        if (videoConnection) {
            break;
        }
    }
    NSLog(@"Requesting capture from: %@", imageOutput);
    [imageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        if (imageDataSampleBuffer != NULL) {
            NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
            UIImage *image = [UIImage imageWithData:imageData];
            self.previewView.image = image;
            self.previewView.hidden = NO;
        }
    }];
    [self saveButtonFlyIn:self.saveButton];
}

#pragma mark - Video capture

- (void)captureVideo {
    NSLog(@"%@", movieOutput.connections);
    [[NSFileManager defaultManager] removeItemAtURL:[self outputURL] error:nil];

    videoConnection = [self connectionWithMediaType:AVMediaTypeVideo fromConnections:movieOutput.connections];

    /* This is where the code is breaking */
    [movieOutput startRecordingToOutputFileURL:[self outputURL] recordingDelegate:self];

- (AVCaptureConnection *)connectionWithMediaType:(NSString *)mediaType fromConnections:(NSArray *)connections {
    for (AVCaptureConnection *connection in connections) {
        for (AVCaptureInputPort *port in [connection inputPorts]) {
            if ([[port mediaType] isEqual:mediaType]) {
                return connection;
            }
        }
    }
    return nil;
}

#pragma mark - AVCaptureFileOutputRecordingDelegate

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error {
    if (!error) {
        //Do something
    } else {
        NSLog(@"Error: %@", [error localizedDescription]);
    }
}

#pragma mark - Recoding Destination URL

- (NSURL *)outputURL {
    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:VIDEO_FILE];
    return [NSURL fileURLWithPath:filePath];
}

#pragma mark - Buttons

- (void)handleLongPressGesture:(UILongPressGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        NSLog(@"Press");
        self.button.backgroundColor = [UIColor greenColor];
        [self captureVideo];
    }
    if (recognizer.state == UIGestureRecognizerStateEnded) {
        NSLog(@"Unpress");
        self.button.backgroundColor = [UIColor redColor];
    }
}

- (UIButton *)createButtonWithTitle:(NSString *)title chooseColor:(UIColor *)color {
    UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(self.view.frame.size.width - 100, self.view.frame.size.height - 100, 85, 85)];
    button.layer.cornerRadius = button.bounds.size.width / 2;
    button.backgroundColor = color;
    button.tintColor = [UIColor whiteColor];
    [self.view addSubview:button];
    return button;
}

- (UIButton *)createSaveButton {
    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(self.view.frame.size.width, 15, 85, 85)];
    button.layer.cornerRadius = button.bounds.size.width / 2;
    button.backgroundColor = [UIColor greenColor];
    button.tintColor = [UIColor whiteColor];
    button.userInteractionEnabled = YES;
    [button setTitle:@"save" forState:UIControlStateNormal];
    [self.view addSubview:button];
    return button;
}

- (void)saveButtonFlyIn:(UIButton *)button {
    CGRect movement = button.frame;
    movement.origin.x = self.view.frame.size.width - 100;

    [UIView animateWithDuration:0.2 animations:^{
        button.frame = movement;
    }];
}

- (void)saveButtonFlyOut:(UIButton *)button {
    CGRect movement = button.frame;
    movement.origin.x = self.view.frame.size.width;

    [UIView animateWithDuration:0.2 animations:^{
        button.frame = movement;
    }];
}

#pragma mark - Save actions

- (void)saveActions {
    [self saveButtonFlyOut:self.saveButton];
    self.previewView.image = nil;
    self.previewView.hidden = YES;
}

@end

The code breaks on this line:

[movieOutput startRecordingToOutputFileURL:[self outputURL] recordingDelegate:self];

Off the top of my head, I'm thinking that it could be a couple of things:

1. Is the data even there (logged it, but can't verify)?
2. Am I initializing the destination url properly?
3. Is the data compatible with the destination? Is that a thing?

Would love your perspectives / fresh sets of eyes / thoughts on how to check, test, or debug this.

Cheers, J

Answer 1

The problem lies in your implementation of -initializeAVItems:

- (void)initializeAVItems {
    //Start session, input
    session = [[AVCaptureSession alloc]init];
    [session setSessionPreset:AVCaptureSessionPresetPhoto];
    ...
}

If you want to use AVCaptureMovieFileOutput to record videos, you cannot set the AVCaptureSession's sessionPreset to AVCaptureSessionPresetPhoto, that's for still images only. For high quality video output I would recommend using AVCaptureSessionPresetHigh.

And it's better to call canSetSessionPreset: before really set it:

session = [AVCaptureSession new];
if ([session canSetSessionPreset:AVCaptureSessionPresetHigh]) {
    session.sessionPreset = AVCaptureSessionPresetHigh;
}