macOS Adapting Apple's QTKit Tutorial for Command Line

[Chris Corbyn]

I've successfully got Apple's basic capture application working with a shiny looking Cocoa GUI around it:

http://developer.apple.com/document...1.html#//apple_ref/doc/uid/TP40004574-CH4-SW2

However, I started looking into QTKit because my attempts to get ffmpeg/ffserver (Linux originating command line tools) to capture from my i-Sight turned out to be impossible (from what I've read ffmpeg doesn't support OS X when it comes to capture devices).

I wanted to build a small CLI tool which captures video from the i-Sight and streams it over HTTP in some compressed/encoded form, just like I could do with ffmpeg/ffserver on Linux. Taking apple's little tutorial linked above I was hopeful that it wouldn't be too difficult and would be a learning experience in Mac programming anyway.

What I've done is built the app and compiled it fine (also spent some time fiddling with some GUI adjustments in IB). Now I'm trying to run it without a GUI. I've pretty much just tried using the Foundation and QTKit frameworks then dropping the QTCaptureView from the QTCaptureSession.

All that happens now is my main() method runs in a split second and the application exits. It all happens so fast the i-Sight light doesn't even blink. How do I, inside a command line Objective-C app, get my QTCaptureSession to stay open until I hit CTRL+C? Do I need to start a new Thread for the session and then sleep the current thread? Pretty much at a loss.

Here's the code I've tried so far:

main.m

#import <Foundation/Foundation.h>
#import "Classes/RecordMeController.h"

int main(int argc, char *argv) {
	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

	RecordMeController *controller = [[RecordMeController alloc]
			initWithOutputFilePath:@"/Users/chris/movie.mov"];
	[controller startRecording];
	
	[controller release];
	
	[pool release];
	
	return 0;
}

Classes/RecordMeController.h

#import <Foundation/Foundation.h>
#import <QTKit/QTKit.h>

@interface RecordMeController : NSObject {
	QTCaptureSession *mCaptureSession;
	QTCaptureDeviceInput *mCaptureDeviceInput;
	QTCaptureMovieFileOutput *mCaptureMovieFileOutput;
	NSString *mMovieSavePath;
}

- (id)initWithOutputFilePath:(NSString *)path;
- (void)startRecording;
- (void)stopRecording;

@end

Classes/RecordMeController.m

#import "RecordMeController.h"

@implementation RecordMeController

- (void)dealloc {
	[mCaptureSession release];
	[mCaptureMovieFileOutput release];
	[mCaptureDeviceInput release];
	[super dealloc];
}

- (id)initWithOutputFilePath:(NSString *)path {

	//Set the save path
	mMovieSavePath = path;
	
	//Start the capture session
	mCaptureSession = [[QTCaptureSession alloc] init];
	
	BOOL success = NO;
	NSError *error;
	
	//Find the default device
	QTCaptureDevice *device = [QTCaptureDevice
						defaultInputDeviceWithMediaType:QTMediaTypeVideo];	
	if (device) {
		success = [device open:&error];
		
		if (!success) {
			//handle error here
		}
		
		//Create a new input for the device
		mCaptureDeviceInput = [[QTCaptureDeviceInput alloc] initWithDevice:device];
		
		//Add the input to the session
		success = [mCaptureSession addInput:mCaptureDeviceInput error:&error];
		
		if (!success) {
			//handle error here
		}
		
		//Create the output
		mCaptureMovieFileOutput = [[QTCaptureMovieFileOutput alloc] init];
		
		//Add the output to the session
		success = [mCaptureSession addOutput:mCaptureMovieFileOutput error:&error];
		
		if (!success) {
			//handle error here
		}
		
		//Tell the output that the controller is this instance
		[mCaptureMovieFileOutput setDelegate:self];
		
		//Start the session now
		[mCaptureSession startRunning];
	}
	
	return self;
}

- (void)startRecording {
	[mCaptureMovieFileOutput recordToOutputFileURL:[NSURL
						fileURLWithPath:mMovieSavePath]];
}

- (void)stopRecording {
}

- (void)captureOutput:(QTCaptureFileOutput *)captureOutput
						didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
						forConnections:(NSArray *)connections
						dueToError:(NSError *)error
{
	//Roughly translates to Finder -> Open -> MyRecorderMovie.mov
//	[[NSWorkspace sharedWorkspace] openURL:outputFileURL];
}

@end

 

[onedanshow]

I know this thread is two years old, but did you ever find a solution to this? I'm currently in the same boat.

I've got a main method that waits for stdin to give it commands and then a Recorder class that does that dirty work, much like your code. I've tried extending my Recorder from NSThread, but it doesn't make a difference.

 

[kainjow]

My guess is if you're not using NSApp's run method then you need to setup the NSRunLoop manually in your main().

 

[chown33]

Google keywords: qtkit command line

On the first page of results:
https://blog.iharder.net/2009/09/14/imagesnap-capturing-a-video-image-with-qtkit-on-snow-leopard/

ImageSnap is a Public Domain command-line tool that lets you capture still images from an iSight or other video source.​

Starting with that source, one could probably modify it to capture movies more easily than figuring the whole thing out from scratch.