For the past week I have been working on Sub It to try get it ready for first release on the Mac App Store.

One of the tools I have put in is a slider to adjust the movie playback rate – similar to the scrub tool in Final Cut Pro.

There were a few hurdles I had to overcome to get this to work.

Initially I realised I would have to subclass NSSlider to be able to detect/grab the MouseDown and MouseUp NSEvents (I wanted the slider to reset to 0 after the user had released the mouse – putting the movie in pause/stop) – googling revealed that NSSlider runs inside its own event loop in the main thread.

Hooking up a delegate to NSSlider subclass allowed me to call actions/methods in the main controller on those Mouse events – eventually I got this to work with the following code (and via Interface Builder I hooked up the delegate property to the my main Controller):

TimeScrubberSlider.h

#import <Cocoa/Cocoa.h>
#import <Foundation/Foundation.h>
 
@interface TimeScrubberSlider : NSSlider {
	IBOutlet id delegate;
}
 
@property (readwrite,retain) id delegate;
 
@end

TimeScrubberSlider.m

#import "TimeScrubberSlider.h"
#import "Controller.h"
 
@implementation TimeScrubberSlider
 
@synthesize delegate;
 
- (void)mouseDown:(NSEvent *)theEvent  {
 
	[delegate doScrubTime:nil];
	[super mouseDown:theEvent];
	[self mouseUp:theEvent];
 
}
 
 
- (void) mouseUp: (NSEvent*) theEvent
{
 
	[self setIntValue:0];
	[delegate doPlay:nil];
 
}
 
@end

This was all working, but the problem was that the time display of the movie would not constantly update – only when the slider was moved would the current time update – not continuously.

So I decided to try attach the updating of the current time display to a separate thread – using NSThread. My thought was that no matter what happened in the main controllers’ thread, this other thread would always do it’s own thing and hopefully not be interrupted.

To get this going I created a method (called ‘launchTimer’) that is called when a file is loaded, and this calls the ‘updateCurrentTime’ method, and this ‘launchTimer’ method is run under the seperate thread. Umm i think that kinda makes sense.

Something along these lines:

snippets from the Controller.m

- (void)setupGUIFromFileRead{
 
	//just a snippet...
 
	//begin timer to update the current frame/time display - as separate thread so nsslider "scrub" can play nicely
	[NSThread detachNewThreadSelector:@selector(launchTimer) 
                             toTarget:self 
                           withObject:nil];
 
}
 
-(void)launchTimer{
 
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSLog(@"startingtimer");
    [NSThread setThreadPriority:1.0];
    updateTimerToggle = YES;
    while (updateTimerToggle) {  // loop until cancelled
        [self doUpdateCurrentTimeDisplay:nil];
        [NSThread sleepForTimeInterval:.1];
    }
    [pool release];
 
}

3 Comments

• At Tue 2, August 2011, Bart wrote:

  Wow Adam, seeing all this code makes my head spin! Amazing that you can get to grips with threading and so. Not the most easy concepts. I wonder if Objective C has any deadlock/lifelock issues in thread synchronization. Keep up the work!

• At Thu 4, August 2011, Adam wrote:

  Hey Bart! Ha it makes my head spin too! From what I gathered looking into threading, NSThread / Cocoa makes it pretty simple to implement. I have used threading in python scripts before, and python too seemed to make it seem quite easy to get going. But really, I know very little about it!

  Once I get my head around the performance side of things, I am sure I will see some memory leaks and performance hits - will see!

  Thanks for your support amigo!

• At Fri 5, August 2011, warwick wrote:

  Hey Adam, I'll Alpha and Beta test it for ya!.

What?

Just knocked together a little app to batch convert selected MP3 files in iTunes to WAV format.

Seems to work pretty well so far.

When the app launches click the button to select the “Output Directory” of the converted files.

Then hit the “Go!” button.

Why?

I was looking for an easy way to batch convert selected tracks in my iTunes library to WAV format, and have them export into a directory (for later use in Final Cut Pro). I came across some Applescripts that would do the conversion within iTunes, but in the end wasn’t really what I was after. I started writing something in Python but then figured it would be a great opportunity to give it a go in Obj-C. It took half a day and I learnt a lot in the time it took to put it together.Hopefully people out there can find a use for the little app, or use the XCode project to build something better!

Requirements:

iTunes must be open and the tracks you want to convert must be selected

*Only tested on Mac OS X 10.6.7

Download:

App: Download MP3toWAV

Xcode Project: Download mp3towavXcodeProj

Notes:

Built using XCode and ObjC. I needed the following to talk to iTunes via OBJC:

• objc-appscript – http://appscript.sourceforge.net/objc-appscript/install.html
• ASDictionary – http://sourceforge.net/projects/appscript/files/

2 Comments

• At Thu 28, April 2011, Warwick wrote:

  Very cool! I'll try it out. Do you have new magic to add or interpolate lost samples from mp3 back into .wav? Lol!

• At Fri 29, April 2011, Adam wrote:

  :) Trying to remember some simple high school mathematics at the moment so it might be a while until I could get that happening!

Spent most of today learning more about NSTableView, memory management and other things Cocoa/Obj-C/xCode.

What came of it?

I made a little app for keeping track of shares – via finance.yahoo.com.

Includes an open/save dialog so you can have a ‘portfolio’ to open again at a later time.

ATM I think it only runs in OS X 10.6.

Download MyShares xcode project

Finally it’s here!
After a complete rewrite in Objective-C I am happy to say that I have a working version of SubIt.

What’s new?
Most noticeably the ability to select QTTracks in your media.
Ability to select a font/style/size before exporting your work.

Download it and let me know what you think and what bugs you have found!

3 Comments

• At Wed 14, October 2009, Nicholas Ward wrote:

  Finally, Way to go Mate! love the logo :p 555

• At Wed 14, October 2009, Adam wrote:

  Cheers man! Thanks again for all your hard work putting the logo together! :)

• At Tue 3, November 2009, ano wrote:

  I wish i had something to write subtitles for!

It turned out I am pretty bad at this so I figured I’d make a little mac app/game to practice with and get back into coding.

Looks like it’s a 64 bit app, and i think it only runs in 10.6.

I might rebuild it for the iPhone.

xcode project:

2 Comments

• At Mon 28, September 2009, Adam wrote:

  haha, it looks like the answer if gives is incorrect!

  fixing it now...

• At Mon 28, September 2009, Adam wrote:

  ok, now it should multiply correctly.

Yesterday I decided I have to give up on PyObjC for the moment and step into the world of Objective-C.

I have got to a point in developing SubIt that I can’t seem to get enough out of the PyObjC bridge to be able to get what SubIt needs.

So now I am in the process of rewriting SubIt in Obj-C.

Obj-C seems weird and complicated and I can’t see why it has to be this way when Python/Ruby seem just so much much easier to understand. Oh well, I have taken the plunge.

I spent most of yesterday reading a great and easy to follow PDF called “Become An Xcoder“, available for free download:
http://www.cocoalab.com/?q=becomeanxcoder

I have been looking at a bunch of podcasts/videos/books and to me this PDF was the quickest/easiest way to get a little up to speed.