Hardware and Software Requirements

QuickTime 7 requires the following minimum configuration:

• Mac OS X v10.4, v10.3, or Windows

• PowerPC G3 or better running at 400 MHz or higher

• At least 256 MB of RAM

New Pro Key Required

QuickTime 7 replaces existing point releases of QuickTime 6 for Mac OS X. A new Pro key is required; QuickTime 6 Pro keys will not unlock the Pro features of QuickTime 7.

New Features of QuickTime 7

This release of QuickTime includes a number of major new features for users, developers, and content creators, including improvements in the QuickTime architecture, file format, user interface, and API. There are significant improvements in the audio, video, and metadata capabilities, as well as a new Cocoa API, and numerous other enhancements.

• Changes to QuickTime Player and QuickTime Pro describes the new user interface for QuickTime Player and QuickTime Pro and some of the changes from previous versions of the player.

• New QuickTime Kit Framework describes a new Cocoa (Objective-C) framework for developing QuickTime applications. This new API opens the world of QuickTime programming to a new group of developers without requiring them to learn the large, complex C/C++ QuickTime API. The new framework encapsulates a tremendous amount of QuickTime functionality in a small, easily-mastered API with a handful of new objects, classes, and methods.

• Audio Enhancements describes the many new audio features of QuickTime 7, including support for multichannel sound, playback, capture, compression, and export of high-resolution audio, a new sound description, and new functions for movie audio control, audio conversion configuration, audio extraction, movie export, and level and frequency metering.

• Video Enhancements describes QuickTime’s new support for frame reordering video compression and the H.264 codec. Frame reordering support is a major advance that involves new sample tables for video, allowing video frames to have independent decode and display times. This allows improved display, editing, and compression of H.264 and other advanced video codecs. A new set of functions and structures are introduced to allow developers to work with samples that have independent decode and display times.

• New Abstractions Layers For OpenGL Rendering describes the new Visual Context, an abstraction layer that eliminates dependence on graphics worlds (GWorlds) and supports rendering directly to engines such as OpenGL.

• Replacing NewMovieFrom... Functions describes the NewMovieFromProperties function, which allows you to set up properties before creating a movie. This function also allows you to create movies that are not necessarily associated with a graphics world, movies that can render their output to a visual context, such as an OpenGL texture buffer, and movies that play to a particular audio device.

• QuickTime Metadata Enhancements and API describes the new QuickTime extensible metadata format, allowing developers to efficiently reference text, audio, video, or other material that describes a movie, a track, or a media. Support is also added for including metadata from other file types in native format; the QuickTime 7 release includes native support for iTunes metadata.

• QuickTime Sample Table API describes the new API for working with QT Sample Tables, a logical replacement for arrays of media sample references. The new API greatly extends the functionality of media sample references, and the new API supports frame reordering compressed media.

• JavaScript Support and Accessibility in Safari describes the JavaScript support for the Safari browser. This means you can now use JavaScript to control QuickTime when web pages are viewed using Safari.

• Other Changes and Enhancements discusses QuickTime 7’s new persistent cache option, which is important for web authors and content developers to understand because it may impact the way that QuickTime content is downloaded and saved from their websites. New updates and fixes to QuickTime for Java are also discussed in this section.

New Directions in QuickTime 7

Key areas of change evident in QuickTime 7 are:

• A shift of emphasis toward a Core Audio approach to sound, and away from the Sound Manager approach, throughout QuickTime.

• A shift of emphasis toward configuring components using component properties and an abstraction layer, or context, and away from the exclusive use of standard dialogs supplemented by direct access to low-level components.

• A shift of emphasis toward a more object-oriented organization, with more high-level functionality in QuickTime itself supporting lighter-weight applications.

In Summary QuickTime 6 through QuickTime 7

The following table summarizes the point releases of QuickTime 6 and the features of QuickTime 7.

New in QuickTime Player

The new QuickTime Player, shown in Figure 2-1, is a native Cocoa application. The intent of this new design is to better integrate QuickTime Player in general with the Mac OS X user experience.

The following are some of the new user-level features available in QuickTime Player:

• H.264 video support. This state-of-the-art, standards-based codec delivers exceptional-quality video at the lowest data rate possible, across the entire bandwidth spectrum.

• New audio and playback controls. Users can use the new A/V Controls window (previously available only to QuickTime Pro users) to adjust settings for the best audio and playback experience. Users can now easily change settings, including playback speed, volume, bass, treble, and balance, as shown in Figure 2-2.

  

  A new video controls panel is also available, as shown in the right portion of Figure 2-2. This option, however, is only available for users with a special video card on Mac OS X v10.4 where Core Image support is provided. The video controls let the user adjust for brightness, color, contrast, and tint.

• Zero-configuration streaming. You no longer need to set your Internet connection speed in QuickTime Preferences. QuickTime automatically determines the best connection speed for your computer. If a connection is lost during streaming, QuickTime automatically reconnects to the server.

• Live resize. Playback continues smoothly as you change the size of the QuickTime Player window. (Note that there may be hardware dependencies that affect the speed and smoothness of live resizing.)

• Multichannel audio. QuickTime Player can now play 24 audio channels––and beyond. With external speakers, you can enjoy the full sound effects of movies and games.

  By accessing the Window > Show Movie Properties dialog and selecting Audio Settings, as shown in Figure 2-3, you can set the volume, balance, bass, and treble for a QuickTime movie. In addition, if you select the sound track property in the dialog, you can set the speaker for each audio channel in that track, specifying the speaker through which the audio can be heard.

  

• All-new content guide. The completely redesigned QuickTime Content Guide provides the latest in news, education, and entertainment on the Internet.

• Screen-reader compatibility. Using VoiceOver, included with Mac OS X v10.4, users with visual disabilities can enjoy QuickTime Player features.

• Spotlight-friendly content. New in Mac OS X v10.4, Spotlight makes it easy to find your QuickTime content. Spotlight can search for movie attributes such as artist, copyright, codec, and so on.

• Easy access to QuickTime Pro. Items available only in QuickTime Pro display “Pro” by their names. If you choose one of these items, you’ll see a definition of the feature and learn how to upgrade to QuickTime Pro. Note that the designation “Pro” is only present when QuickTime Player is not the Pro version.

New in QuickTime Pro

The following are some of the new user-level features available in the Pro version of QuickTime Player:

• Creating H.264 video. Users can take advantage of this codec for a variety of video needs, ranging from HD (high definition) to 3G (for mobile devices). This new codec provides better quality at lower bandwidth, enabling users to deliver high-quality video over the Internet.

• Creating multichannel audio. Users can create a rich multimedia experience by labeling each audio channel (for example, Left, Right, Left Surround, LFE, and so on), as shown in Figure 2-3. QuickTime automatically mixes the audio to work with the speaker setup of each user.

• Recording audio and video. With a digital video camera connected to your computer, you can enrich your email messages with video clips. In addition, with enhanced recording of audio and video, users can add narration, for example, to their slide shows.

• Sharing movies. Users can easily create a movie file for sending via email or posting to your .Mac HomePage. Select File > Share and a dialog appears that lets you choose a maximum size for the attached movie you want to share and then exports the movie to either your Mail program or to your .Mac HomePage, as shown in Figure 2-4.

  

• Full screen playback enhancements. Full screen mode now provides floating Dashboard-style controls similar to the controls available for DVD Player. These include pause, play, stop, fast forward, and rewind, as illustrated in Figure 2-5. Users move the pointer to display the controller; after a few seconds, the controller fades away. Note that the controller does not appear with interactive movies when the mouse is moved, so that it does not interfer with movie content. Users can press the keyboard control-C to make it appear or disappear immediately. This new zooming transition, enabling you to go in and out of Full Screen, is dependent on the user’s computer hardware, as well as the media being played back.

  

  Users can access full screen mode by choosing the View > Full Screen or using its keyboard equivalent. To display the DVD-style full screen controls, users choose QuickTime Player > Preferences > Full Screen and select “Display full screen controls,” as shown in Figure 2-6.

  

• Concurrent exports. Users can export multiple files at once—and continue with their next playback or editing task. Figure 2-7 shows the default export settings for exporting a movie to a QuickTime movie.

  

• The export options enable Pro users to export to a variety of image, text, audio, and movie formats, as shown in Figure 2-8.

  

• Enhanced and redesigned interface for movie settings. The Movie Properties window has been redesigned to facilitate movie authoring. Figure 2-9 illustrates the Movie Properties dialog, with annotations of the movie selected.

  

• New options for image manipulation in the Visual Settings pane of the Movie Properties dialog of a video track, as shown in Figure 2-10.

  

  In addition, users are provided with other options to manipulate and control image transparency in QuickTime movies and image files, shown in Figure 2-11.

Other Changes and Enhancements

QuickTime Preferences now has the option “Use high quality video setting when available.” Users can set this as the default for displaying high-quality video tracks, such as DV. Figure 2-12 shows the options available in the General pane of QuickTime Player Preferences.

Figure 2-13 shows the new File menu in QuickTime Player. The Open File command enables users to open any of a number of digital media types that QuickTime supports, including movies, still images, VR panoramas, Flash, and so on.

Choosing the File > New Movie Recording menu item enables you to record video from an external digital video camera. Recording is transparent and easy to use, as QuickTime automatically recognizes the device and opens a new QuickTime Player with a red button in the lower center, as shown in Figure 2-14. The Player also displays the current recording duration, as well as the size of the recording in megabytes.

Choosing the File > New Audio Recording menu item enables you to record audio from an external or internal audio device. Once recording begins, a new QuickTime Player appears, as shown in Figure 2-15.

To change the video or audio source for your recording, or to specify the quality of recording you want, you choose QuickTime Player > Preferences > Recording, as shown in Figure 2-16.

The Save dialog that the Save As command opens now has a “Make movie as a self-contained,” selected by default, which is a change from previous versions of QuickTime Player.

Choosing the File > Update Existing Software menu item shown in Figure 2-17 lets you update the version to the latest version of QuickTime available through Software Update.

The Edit menu has changed from previous versions of QuickTime, as shown in Figure 2-18.

Support for multiple undos is now provided. There is a command Trim to Selection (instead of Trim) and there is no longer a Replace command (users can’t do delete and paste as a single operation).

The Movie menu has been renamed and is now the View menu, as shown in Figure 2-19. The Show Movie Properties command has been moved to the Windows menu. Note that this overrides any full screen settings made in user preferences for the current presentation only.

The Present Movie command now opens a sheet as shown in Figure 2-20. The same functionality as in previous versions is provided.

The Window menu (Figure 2-21) now provides commands for getting movie properties and showing audio/video controls.

Choosing the Window > Show Movie Properties menu item and selecting Video Track 1 (shown in Figure 2-22) enables you to specify certain properties of that track. For example, if you select Annotations and want to add a field, you have multiple choices, including Album, Artist, Author, and so on.

Choosing the Window > Show Movie Properties menu item and selecting Video Track 1 (shown in Figure 2-23) with Other Settings selected enables you to specify certain properties of that track, including language, preloading of the track, caching, and so on.

The movie properties window has been reorganized, as shown in Figure 2-24. The Presentation pane provides users with four choices for presenting movie, as well as options for displaying various types of movie controllers.

• New selection handles and fade in/out behavior. When the user moves the mouse over a selection of the movie, ticks appear that indicate you can make a selection over that area. When you move the mouse over the playbar, the movie will fade the selection indicators in and out. Users can also set in and out points now by placing the current time marker and typing I or O.

New Abstraction Layer For Audio

QuickTime 7 introduces the audio context––a new abstraction that represents playing to an audio device.

As defined, a QuickTime audio context is an abstraction for a connection to an audio device. This allows you to work more easily and efficiently with either single or multiple audio devices in your application.

To create an audio context, you call QTAudioContextCreateForAudioDevice and pass in the UID of the device, which is typically a CFString. An audio context is then returned. You can then pass that audio content either into NewMovieFromProperties, as you would pass in a visual context, or you can open your movie however you would normally open it and call SetMovieAudioContext. What that does is route all the sound tracks of the movie to that particular device.

Note that if you want to route two different movies to the same device, you cannot use the same audio context because the audio context is a single connection to that device. What you do is call QTAudioContextCreateForAudioDevice again and pass in the same device UID to get another AudioContext for the same device, and pass that to your second movie.

High-Resolution Audio Support

High-resolution audio makes use of an enhanced sound description with the ability to describe high sampling rates, multiple channels, and more accurate audio representation and reproduction.

Significantly, the new sound description has larger fields to describe the sampling rate and number of channels, so that the sound description is no longer the limiting factor for these characteristics.

The sound description has built-in support for variable-bit-rate (VBR) audio encoding with variable-duration compressed frames. Extensions to the sound description allow you to describe the spatial layout of the channels, such as quadraphonic and 5.1 surround sound, or to label channels as discrete––that is, not tied to a particular geometry. For more information, see “SoundDescriptionV2”.

New movie audio properties include a summary channel layout property, providing a nonredundant listing of all the channel types used in the movie—such as L/R for stereo, or L/R/Ls/Rs/C for 5-channel surround sound—and a device channel layout, listing all the channel types used by the movie’s output device.

Figure 2-28 shows the layout of surround speakers. The terminology is defined in Table 1-1.

The new sound description is supported by the data types and structures used in the Core Audio framework for Mac OS X (see Core Audio documentation). While the Core Audio API itself is not available to Windows programmers, QuickTime for Windows may include the relevant data structures, such as audio buffers and stream descriptions, audio time stamps and channel layouts, and so on, described in the Core Audio documentation.

A suite of functions has been included to support the handling of sound descriptions opaquely.

Sound Description Creation and Accessor Functions

QuickTime 7 provides new functions that let you create, access, and convert sound descriptions.

Sound descriptions can take three basic inputs: an AudioStreamBasicDescription, a channel layout, and magic cookie. Sound descriptions are now treated as if they are opaque. In QuickTime 7, when you are handed a sound description, for example, you don’t have to go in and look at the version field.

If you want to create a sound description, you can simply hand it an AudioStreamBasicDescription, an optional channel layout if you have one, and an optional magic cookie if you need one for the described audio format. Note that it is the format (codec) of the audio that determines whether it needs a magic cookie, not the format of the sound description.

By calling QTSoundDescriptionCreate, you can make a sound description of any version you choose––for example, one that is of the lowest possible version, given that it is stereo and 16-bit, or one of any particular version you want or request.

The main point about the new API is the capability provided to create a sound description and the usage of new property getters and setters. To accomplish this, follow these steps:

1. Get an AudioStreamBasicDescription from a sound description.

2. Get a channel layout from a sound description (if there is one).

3. Get the magic cookie from magic cookie (if there is one).

At this point, you have all the information you need to talk to Core Audio about this audio. You can also:

1. Get a user-readable textual description of the format described by the SoundDescription.

2. Add or replace a channel layout to an existing sound description. For example, this is what QuickTime Player does in the properties panel where the user can change the channel assignments.

3. Add a magic cookie to a sound description. (This is not needed very often unless you are writing a movie importer, for example.)

To convert an existing QuickTime sound description into the new V2 sound description, you call QTSoundDescriptionConvert. This lets you convert sound descriptions from one version to another.

For a description of versions 0 and 1 of the SoundDescription record, see the documentation for the QuickTime File Format.

For a description of version 2 of the SoundDescription record, see “SoundDescriptionV2”. For details of the sound description functions, see QTSoundDescriptionCreate and QTSoundDescriptionConvert.

Audio Playback Enhancements

In addition to playing back high-resolution audio, QuickTime 7 introduces the following audio playback enhancements:

• The ability to play movies at a nonstandard rate without pitch-shifting the audio.

• Getting and setting the gain, balance, and mute values for a movie, or the gain and mute values for a track.

• Providing audio level and frequency metering during playback.

Audio Conversion, Export, and Extraction

The new audio extraction API lets you retrieve mixed, uncompressed audio from a movie.

Note that the audio extraction API currently only mixes audio from sound tracks. Other media types, such as muxed MPEG-1 audio inside a program stream, are not currently supported.

To use the audio extraction API, follow these steps:

1. Begin by calling MovieAudioExtractionBegin. This returns an opaque session object that you pass to subsequent extraction routines.

2. You can then get the AudioStreamBasicDescription for the audio or layout. Note that some properties are of variable size, such as the channel layout, depending on the audio format, so getting the information involves a two-step process.

   1. First, you call MovieAudioExtractionGetPropertyInfo to find out how much space to allocate.

   2. Next, call MovieAudioExtractionGetProperty to obtain the actual value of the property.

3. You can use the AudioStreamBasicDescription to specify a different uncompressed format than Float 32. This causes the extraction API to automatically convert from the stored audio format into your specified format.

4. Use the MovieAudioExtractionSetProperty function to specify channel remapping––that is, a different layout––sample rate conversion, and preferred sample size. You can also use this function to specify interleaved samples (default is non-interleaved) or to set the movie time to an arbitrary point.

Note that there are basically two things you set here: an audio stream basic description (ASBD) and a channel layout. (ASBD sets the format, sample, number of channels, interleavings, and so on.)

Setup is now complete. You can now make a series of calls to MovieAudioExtractionFillBuffer to receive uncompressed PCM audio in your chosen format.

1. The default is for the first call to begin extracting audio at the start of the movie, and for subsequent calls to begin where the last call left off, but you can set the extraction point anywhere in the movie timeline by calling MovieAudioExtractionSetProperty and setting the movie time.

2. MovieAudioExtractionFillBuffer will set kMovieAudioExtractionComplete in outFlags when you reach the end of the movie audio.

3. You must call MovieAudioExtractionEnd when you are done. This deallocates internal buffers and data structures that would otherwise continue to use memory and resources.

A caveat: Ideally, the uncompressed samples would be bitwise identical whether you obtained the samples by starting at the beginning of the movie and iterating through it, or by randomly setting the movie time and extracting audio samples. This is typically the case, but for some compression schemes the output of the decompressor depends not only on the compressed sample, but the seed value in the decompressor that remains after previous operations.

The current release of QuickTime does not perform the necessary work to determine what the seed value would be when the movie time is changed prior to extracting audio; while the extracted audio is generally indistinguishable by ear, it may not always be bitwise identical.

For details about audio conversion, export, and extraction, refer to the information about the following functions:

• MovieAudioExtractionBegin

• MovieAudioExtractionGetPropertyInfo

• MovieAudioExtractionGetProperty

• MovieAudioExtractionSetProperty

• MovieAudioExtractionFillBuffer

• MovieAudioExtractionEnd

Standard Audio Compression Enhancements

QuickTime 7 introduces a new standard compressor component, StandardCompressionSubTypeAudio, that adds the ability to configure high-resolution audio output formats. It uses Core Audio internally instead of the Sound Manager, and has a full set of component properties to make configuration easier, especially when the developer wishes to bring up an application-specific dialog, or no dialog, rather than the typical compression dialog.

This component essentially replaces the StandardCompressionSubTypeSound component, which is limited to 1 or 2 channel sound with sampling rates of 65 kHz or less. That component is retained for backward compatability with existing code, but its use is no longer recommended.

The StandardCompressionSubTypeAudio component is configured by getting and setting component properties, instead of using GetInfo and SetInfo calls. These properties have a class and ID, instead of just a single selector.

The component property API allows configuration at any level of detail without requiring a user interface dialog or direct communication with low-level components.

For details, refer to the sections SGAudio Component Property Classesand SGAudio Component Property IDs.

If you use MovieExportToDataRefFromProcedures, your getProperty proc will need to support some of these property IDs as new selectors. Note that the Movie Exporter getProperty proc API is not changing to add a class (the class is implied).

Audio Export Enhancements

Some movie export components now support high-resolution audio.

Export of high-resolution audio is transparent at the high level. If you export from a movie containing high-resolution audio to a format whose export component supports it, the transfer of data is automatic; if the export component does not support high-resolution audio, mix-down, resampling, and sound description conversion are automatic.

Export at the lower levels requires some additional code. Your application must “opt in” to the new audio features explicitly if it talks directly to an export component instance. (This is to prevent applications that have inadvisedly chosen to “walk” the opaque atom settings structure from crashing when they encounter the new and radically different structure.) The following code snippet (Listing 2-1) illustrates the opt-in process.

Listing 2-1  Opting in for high-resolution audio export

ComponentInstance exporterCI;

ComponentDescription search = { ’spit’, ’MooV’, ’appl’, 0, 0 };

Boolean useHighResolutionAudio = true, canceled;

OSStatus err = noErr;

Component c = FindNextComponent(NULL, &search);

exporterCI = OpenComponent(c);

// Hey exporter, I understand high-resolution audio!!

(void) QTSetComponentProperty(// disregard error

        exporterCI,

        kQTPropertyClass_MovieExporter,

        kQTMovieExporterPropertyID_EnableHighResolutionAudioFeatures,

        sizeof(Boolean),

        &useHighResolutionAudio);

err = MovieExportDoUserDialog(exporterCI, myMovie, NULL, 0, 0, &canceled);

For additional details, see “Movie Exporter Properties”.

Audio Capture Enhancements

There is a new sequence grabber channel component (’sgch’) subtype for audio, SGAudioMediaType (’audi’), which allows capture of high-resolution audio, supporting multi-channel, high sample rate, high accuracy sound. This is intended to replace the older SoundMediaType component.

The new audio channel component has a number of noteworthy features, including:

• audio capture to VBR compressed formats

• enabling or disabling of source channels on a multi-channel input device

• mix-down and remapping of multi-channel audio source material

• discrete and spatial labeling of channels (for example, 5.1 or discrete)

• audio format and sample rate conversion during capture

• sharing of audio input devices among multiple sequence grabber audio channels

• sharing of audio playback devices among multiple sequence grabber audio channels

• notification of audio device hotplug/unplug events

• audio preview of source data or compressed data

• splitting audio channels from a record device to separate tracks in a movie

• redundant capture of multichannel audio to separate tracks in a movie (with independent data rates and compression settings)

• client callbacks of audio pre- and post-mixdown, and pre- and post-conversion with propagation of audio time stamps and audio samples to interested clients

• improved A/V sync

• improved threading model compared with the legacy SoundMediaType

• lower latency audio grabs

• reduced dependency on frequent SGIdle calls

This new, advanced functionality makes extensive use of Core Audio methodology and data structures.

Sequence Grabber Audio Channel Mapping

Figure 2-29 is a high-level diagram that shows some of the internal workings of the sequence grabber audio channel, such as the Core Audio matrix mixer and the audio converter that lets you convert, compress, and interleave audio, and then queue the audio. From the queue, the audio can be written to disk in desired chunk sizes. One distinct advantage of this process is that you can take a single device and share it among multiple channels. This results in simultaneous recording from multiple devices into multiple tracks in a QuickTime movie. In addition, you can record multiple tracks from a single device.

Figure 2-30 illustrates a usage case that involves client channel mapping. This shows how a client can instantiate multiple sequence grabber audio channels that share a recording device. This enables the “splitting” of device channels across multiple tracks in a QuickTime movie. In Figure 2-30, there is single recording device, with four channels. The first two channels record into Track 1 in a QuickTime movie. The second sequence grabber audio channel, which records into Track 2 in a QuickTime movie, only wants channel 4 from the recording device, so that you can get one stereo track and one mono track.

In this example, device Track 0 will get into Movie Track 1, while Movie Track 3 has only one slot to fill. You can mix and match different channel map valences in such a way as to disable certain tracks in a movie and get submixes, for example. In code, it looks like this:

SInt32 map 1 [ ] = { 0, 1 };

SInt32 map 2 [ ] = { 3 };

Figure 2-31 shows another usage case that also involves client channel mapping.

A sequence grabber audio channel shown in the illustration can get four channels from a device in any order that makes sense for the client. Consider, for instance, a device that supports four-channels of audio. Using the channel map property IDs (SGAudio Component Property IDs), you can reorder channels from a recording device to a desired movie channel valence. In code, it looks like this:

SInt32 map [ 4 ] = { 3, 2, 1, 0 };

Figure 2-32 shows another example of what you can do with the feature of channel mapping, in this case mult’-ing, that is, duplicating channels from a recording device into multiple output channels in QuickTime movie tracks. For instance, you can take advantage of this channel mapping feature if you have one recording device and two sequence grabber audio channels, and they’re both going to make the same movie. The first sequence grabber audio channel wants the first stereo pair twice (1, 2, 1, 2), while the second wants the second stereo pair twice (3, 4, 3, 4). In code, it looks like this (zero-based indexing):

SInt32 map 1 [ ] = { 0, 1, 0, 1 };

SInt32 map 2 [ ] = { 2, 3, 2, 3 };

Figure 2-33 illustrates the what you can do with multiple mixes. Because you can duplicate device channels onto multiple output tracks, you can create a movie containing multiple mixes of the same source material.

This is useful for a recording situation where you have a six channel recording device and are presenting 5.1 material. You could make a QuickTime movie that has four tracks in it. In this case, the first track is getting the raw, unmixed source––that is, channels one through six. You will have a six discrete channel track, meaning that the first channel plays out to the first speaker, the second channel out to the second speaker, and so on.

In sequence grabber audio channel #2, you’ll get a 5.1 mix and apply spatial orientation to the six channels, specifying the speakers to which the audio will play. All four tracks are going into a QuickTime movie. Sequence grabber audio channel #3 presents a stereo mix-down, while sequence grabber audio channel #4 presents a mono mix-down.

Figure 2-34 shows channel mapping with multi-date rates, similar to multiple mixes, except that you can also apply compression to the mixes. As a result, you can broadcast multiple streams at once.

Figure 2-35 shows sequence grabber audio callbacks, which are analogous to the VideoMediaType sequence grabber channel video bottlenecks. The callbacks provide developers with different places in the audio chain where they can “pipe in” and look at the samples.

Figure 2-36 shows sequence grabber audio callbacks, with real-time preview. Clients can specify what they want to preview, using the sequence grabber channel play flags.

Using Sequence Grabber Audio Features

To make use of the new sequence grabber audio features, follow these steps:

1. Instantiate a sequence grabber channel of subtype SGAudioMediaType (’audi’), by calling SGNewChannel(sg, SGAudioMediaType, &audiChannel).

2. Use the QuickTime component property API to obtain a list of available input and preview devices from the sequence grabber channel, by getting the property kQTSGPropertyID_DeviceListWithAttributes (’#dva’).

3. Use the same component property API to get the input device characteristics and set the desired audio format and device settings. See “SGAudio Component Property Classes” and “SGAudio Component Property IDs” for details. Note that this is sometimes a two-stage process, as next described.

4. 1. Use QTGetComponentPropertyInfo to determine the size of the property value.

   2. Allocate the necessary container and use QTGetComponentProperty to obtain the actual value. This is necessary with properties such as channel layout, which is a variable length structure.

5. Call SGStartRecord or SGStartPreview, enabling the sequence grabber, and then make periodic calls to SGIdle.

If you are capturing only sequence grabber audio media, it is no longer necessary to make extremely frequent calls to SGIdle, since this function is only used to write the samples to storage, not to capture data from the input device. When capturing video or using an old-style sequence grabber sound media component, however, you must still call SGIdle frequently (at a frequency greater than the video sample rate or the sound chunk rate).

By setting the appropriate sequence grabber channel properties and setting up a callback, you can examine samples at various points in the input chain, such as premix, postmix, preconversion, and postconversion. For details, see SGAudioCallbackProc, SGAudioCallbackStruct, “SGAudio Component Property Classes” and “SGAudio Component Property IDs”.

Frame Reordering Video

QuickTime 7 adds support for frame reordering video compression. This is a major advance that involves new sample tables for video to allow video frames to have independent decode and display times.

The result of using frame reordering for video compression is improved display, editing, and capture in H.264 and other advanced video codec formats. Enhancements include a new API for working with media sample times, adding and finding samples, and a new Image Compression Manager (ICM) API.

CFDictionaryRef attributesDictionary = NULL;

err = ICMCompressionSessionGetProperty(

    session,

    kQTPropertyClass_ICMCompressionSession,

    kICMCompressionSessionPropertyID_CompressorPixelBufferAttributes,

    sizeof(CFDictionaryRef),

    &attributesDictionary,

    NULL);

if (attributesDictionary) {

    // ...use...

    CFRelease(attributesDictionary);

}

H.264 Codec

The H.264 codec is the latest standards-based video codec. Published jointly by the ITU as H.264––Advanced Video Coding, and by ISO as MPEG-4 Part 10––Advanced Video Coding, the H.264 codec promises better image quality at lower bit rates than the current MPEG-4 video codec, and also better live streaming characteristics than the current H.263 codec.

This represents a significant increase in quality and performance, while operating in a standards-based framework.

QuickTime 7 for Mac OS X v10.4 includes a QuickTime decompressor component and an exporter component for creating and playing H.264-encoded video in QuickTime.

The H.264 codec makes use of QuickTime 7’s new support for frame reordering video compression.

New Abstractions Layers For OpenGL Rendering

QuickTime 7 introduces the visual context—an abstraction that represents a visual output destination for a movie—and the OpenGL texture context, an implementation of the visual context that renders a movie’s output as a series of OpenGL textures.

Using NewMovieFromProperties

To instantiate a movie using NewMovieFromProperties, follow these steps:

1. Pass in a CFString file path, a URL, or set up a data reference, just as you would for NewMovieFromDataRef or one of the other NewMovieFrom_ functions.

2. Next, set up a visual context for the movie to use by calling a function that creates a context of a the desired type, such as QTOpenGLTextureContextCreate. Similarly, you can set up an audio context if you want a device other than the default device.

3. Call NewMovieFromProperties, passing in the data reference for the movie and the QTVisualContextRef for the visual context, plus any appropriate properties listed in the QTNewMoviePropertyArray.

Properties are passed in using a QTNewMoviePropertyElement struct, which specifies the property class and property ID of each property.

The movie will automatically retain the visual context, so if your application does not need to work with the context directly, you may release it now.

For additional details, see:

• QTNewMoviePropertyArray

• QTNewMoviePropertyElement

• NewMovieFromProperties

How It Works

Metadata is encapsulated in an opaque container and accessed using a QTMetDataRef. A QTMetaDataRef represents a metadata repository consisting of one or more native metadata containers. The QuickTime metadata API supports unified access to and management of these containers.

Each container consists of some number of metadata items. Metadata items correspond to individually labeled values with characteristics such as keys, data types, locale information, and so on. Note that what QuickTime calls items are sometimes referred to as attributes or properties in other metadata systems.

You address each container by its storage format (kQTMetaDataStorageFormat). Initially, there is support for classic QuickTime user data items, iTunes metadata, and a richer QuickTime metadata container format. A QTMetaDataRef may have one or all of these. No direct access to the native storage containers is provided.

QTMetaDataRefs may be associated with a movie, track or media. This parallels user data atoms usage but provides access to other kinds of metadata storage at those levels.

A metadata item is assigned a runtime identifier (QTMetaDataItem) that along with the QTMetaDataRef identifies the particular item (and value) across all native containers managed by the QTMetaDataRef.

Each item is addressed by a key, or label. The key is not necessarily unique within its container, as it is possible to have multiple items with the same key (for example, multiple author items). Functions exist to enumerate all items or only items with a particular key.

Because a QTMetaDataRef may provide access to different native metadata containers with differing key structures—a four-char-code for one, a string for another, and so on—the key structure is also specified. A QTMetaDataKeyFormat indicates the key structure to functions that take keys. This also supports container formats that allow multiple key structures or multiple versions of key structures.

To allow unified access across disparate containers, you can specify a wildcard storage format. This can be used for operations such as searches across container formats. A special key format called kQTMetaDataKeyFormatCommon indicates one of a set of common keys that can be handled by multiple native containers (for example, copyright).

Both modes of operation are illustrated in Figure 2-37.

Advantages of the New Metadata Format

The QuickTime metadata format is inherently extensible. Instead of a set of structures and enumerated parameters, the metadata API uses a set of properties that can be enumerated, and whose characteristics can be discovered, dynamically at runtime. This is analogous to the QuickTime component property function in that you first get the property info, such as its size and format, and then you allocate the appropriate container or structure to get or set the actual property.

The new QuickTime metadata format and API consist of the following structures, enumerations, and functions, grouped in sections followed by the specific functions:

• “Metadata Format Constants”

• “Metadata Property IDs”

• “Metadata Key Constants”

• “Metadata Error Codes”

• QTCopyMovieMetaData

• QTCopyTrackMetaData

• QTCopyMediaMetaData

• QTMetaDataAddItem

• QTMetaDataGetItemCount

• QTMetaDataGetItemProperty

• QTMetaDataGetItemPropertyInfo

• QTMetaDataGetItemValue

• QTMetaDataGetNextItem

• QTMetaDataGetProperty

• QTMetaDataGetPropertyInfo

• QTMetaDataRetain

• QTMetaDataRelease

• QTMetaDataRemoveItem

• QTMetaDataRemoveItemsWithKey

• QTMetaDataSetItem

• QTMetaDataSetItemProperty

• QTMetaDataSetProperty

New Persistent Cache Option

QuickTime 7 introduces a new persistent cache option, which is enabled in the System Preferences > QuickTime > Browser panel, as shown in Figure 2-38. Users, web authors, and web content developers should understand the consequences of this new option because it may impact the way that QuickTime content is downloaded and saved from their websites. The reason is that QuickTime’s caching behavior has changed in this release.

Updates to QuickTime for Java

QuickTime for Java (QTJ) is now fully supported in QuickTime 7. QTJ is now installed by default in QuickTime 7.

This release includes a number of important bug fixes requested by QuickTime for Java developers. These are as follows:

• Major fixes for issues related to drawing and correct QTComponent rendering

• Compatibility with headless applications

• Fixes for issues related to movie progress procedures and movie exporting

• Fixes for Applet issues, including support for MPEG video playback in an applet

• Support for 2-byte character file names

• Security fixes

Support for Quartz Composer

QuickTime can read Quartz Composers. Also, Quartz Composer compositions can be exported as QuickTime movies.

You can accomplish this either by using the Export menu command in the Quartz Composer Editor, or by opening the composition in QuickTime Player and saving it as a movie.