Create Custom Controls for the MyMediaPlayer Project

Adding custom controls for movie playback to your media player project is relatively straightforward. You define the instance variables in your declaration file and then launch Interface Builder to add the controls from the library of available plug-in controls and wire up the play and pause buttons to the QTMovieView object for custom control of movie playback.

Working with the MyMediaPlayer sample project you constructed in Extending the Media Player Application, in the steps that follow, you create custom controls for your player application.

1. In your MyMediaPlayer Xcode project, open the MyDocument.h declaration file.

2. Declare an mMovie instance variable that points to a QTMovie object.

3. Declare an mMovieWindow instance variable that points to an NSWindow object as an Interface Builder outlet.

   IBOutlet NSWindow *mMovieWindow;

4. Declare an mMovieView instance variable that points to a QTMovieView Interface Builder outlet.

   IBOutlet QTMovieView *mMovieView;

   At this point, the code in your MyDocument.h file should look like this.

   #import <Cocoa/Cocoa.h>

   #import <QTKit/QTKit.h>

   @interface MyDocument : NSDocument

   {

   QTMovie *mMovie;

   IBOutlet NSWindow *mMovieWindow;

   IBOutlet QTMovieView *mMovieView;

   }

   @end

5. Save your file.

Now you’re ready to add the control buttons you need to customize media playback of content in your Xcode project.

Select Control Objects in Interface Builder

To add buttons in Interface Builder:

1. Launch Interface Builder 3.2 and open the MyDocument.xib file in your Xcode project window.

2. Resize the QTMovieView object in your window so that you allow space at the bottom for placement of your control buttons.

3. Choose Tools > Library to open the Interface Builder library of controls and scroll down until you find the oval push button (NSButton) controls you need for your project.

   • Select and drag two buttons, which you can name Play and Pause, into the lower region of your window.

   • Control-drag the Play button to the play: action of the QTMovieView object and the Pause button to the pause: action of the QTMovieView object to wire up and connect both objects.

   • Click the QTMovieView object.

4. Modify the attributes of the QTMovieView object.

   • Choose Tools > Inspector.

   • In the Inspector panel, select the Movie View Attributes icon, which appears as the first icon in the row at the top of the panel.

   • Make sure the Show Controller checkbox is unselected.

5. Save your the file in Interface Builder and return your Xcode project.

Build and Compile Your Project in Xcode

After you’ve completed the sequence of steps, simply build and run the MyMediaPlayer project in Xcode. When the player launches, open and play any QuickTime movie of your choice.

Locate a .mov file and launch the movie from the File > Open menu in your media player application. Use the custom controls you’ve added to play and pause the playback of media content.

Using Movie Attributes to Customize Movie Operations

If you open and review the QTMovie Class Reference, you find a series of tables that describe movie attributes. These movie attributes are some of the most powerful features of the QTKit API, in that you can access the data in a QTMovie object, which is stored as attributes, by using an attribute key. The data encapsulated as attributes can be included in a dictionary and used appropriately in your code to handle a number of important tasks.

Whenever you instantiate a new QTMovie object, you can use its specified attributes to perform certain tasks. For example, you can use movie attributes in a dictionary to specify:

• The location of the movie data

• How the movie is to be instantiated

• The playback characteristics of the movie or other properties of the QTMovie object

Here are some of the keys that specify attributes of movie data you can access and manipulate in your application. The complete list of movie attributes is available in the QTKit Framework Reference.

In Extending the Media Player Application, you already accessed and set one of the important attribute keys available in the QTMovie class when you added the following single line of code to your media player application:

    [newMovie setAttribute:[NSNumber numberWithBool:YES] forKey:QTMovieEditableAttribute];

By setting that attribute, you enabled your media player to support simple cut, copy, and paste editing on the movie.

Accessing Media Services in QuickTime X

If you need to play back media, you can take advantage of the high-performance playback efficiency provided by QuickTime X in OS X v10.6. You gain access to the media playback services through the QTKit framework.

QuickTime X is a new media architecture developed by Apple that provides media services for QTKit application developers who need to play back audio/video media. Available in OS X v10.6, it is specifically designed for efficient, high-performance playback of audio/video media, with optimized support for modern codecs such as H.264 and AAC.

Using QuickTime X, you can open a media file, gather information about the playback characteristics of the movie (such as its duration, the codecs used, and thumbnail images), display the movie in a view, and control the loading and playback of that movie. However, movies using the new media services cannot be edited or exported.

In OS X v10.6, two new movie attributes are defined. The first attribute, QTMovieOpenAsyncRequiredAttribute, indicates whether a QTMovie object must be opened asynchronously. The second attribute, QTMovieOpenForPlaybackAttribute, indicates whether a QTMovie object will be used only for playback and not for editing or exporting.

The default behavior of QTMovie is to open movies that can be made editable and exportable. You pass the QTMovieOpenForPlaybackAttribute key with the value NSNumber numberWithBool:YES in the dictionary of attributes passed to initWithAttributes:error:. This indicates that you are interested only in playing the movie. If you don’t need to do editing or exporting, QTMovie may be able to select more efficient code paths.

To open and playback a movie file, you use the following code:

 - (void)windowControllerDidLoadNib:(NSWindowController *) aController

    {

        [super windowControllerDidLoadNib:aController];

        if ([self fileName]) {

            NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:

                                        [self fileName], QTMovieFileNameAttribute,

                                        [[NSNumber numberWithBool:YES],

                                        QTMovieOpenForPlaybackAttribute, nil];

            movie = [[QTMovie alloc] initWithAttributes:attributes error:NULL];

            [movieView setMovie:movie];

            [movie release];

            [[movieView movie] play];

        }

    }

Because the attributes dictionary contains a key-value pair with the QTMovieOpenForPlaybackAttribute key and the value YES, QTKit uses the new media services, if possible, to play back the media content in the selected file.

Summary

In this chapter you learned how to:

• Customize the functionality of the MyMediaPlayer application, enabling you to create custom start and stop controls for the playback of QuickTime movie or audio files.

• Use movie attributes to access the data in a QTMovie object, enabling you to access and manipulate movie data in your application

• Modify the MyMediaPlayer application for the playback of movies and media at their original or natural size.

• Access the new media services available in QuickTime X and OS X v10.6.

Next Coding Assignments

If you’ve worked through the coding examples in the first three chapters of this tutorial, you are well on your way toward mastering the skills you need to have in order to develop applications for media playback.

The next three chapters introduce you to the methods and classes in the QTKit API that let you do capture and recording of media content. You build a recorder application that is simple to design and implement, yet powerful in its functionality.

Beyond that, you add code to the recorder application to support the capture of DV video and audio media, and then create another application that enables you to capture and record still images, using the techniques employed by the movie industry for stop motion animation. After recording those still images, you’ll be able to output the content to a QuickTime movie, creating some unusual, animated effects.