TweetFollow Us on Twitter

State Property 2

Volume Number: 21 (2005)
Issue Number: 12
Column Tag: Programming

QuickTime Toolkit

State Property 2

by Tim Monroe

Opening QuickTime Movies using Properties

In the previous QuickTime Toolkit article ("State Property" in MacTech, November 2005), we learned how to work with the QuickTime properties functions introduced in QuickTime 6.4 and considerably expanded in QuickTime 7. We saw how to get and set movie properties using those functions, and we saw how to install a property listener so that our applications can be informed about changes to some of those movie properties. Currently, only two small sets of movie properties are gettable or settable or listenable using those functions. These are a handful of visual properties (hue, saturation, brightness, and contrast) and a smaller handful of audio properties (gain, mute, and balance). So why is the header file Movies.h chock full of identifiers for other property classes and other property types within those classes?

The answer is that those additional properties are intended for use by other functions, and in particular by the NewMovieFromProperties function, which was introduced in QuickTime 7. NewMovieFromProperties is intended as a replacement for the plethora of existing "NewMovieFrom" functions, including

NewMovie, 
NewMovieFromFile, 
NewMovieFromHandle, 
NewMovieFromDataRef, 
NewMovieFromStorageOffset, 
NewMovieFromDataFork, 
NewMovieFromDataFork64, 
NewMovieFromScrap, 
and NewMovieFromUserProc. 

The basic idea is that we first specify an array of properties that we'd like our new movie to have, and then we call NewMovieFromProperties. This allows us to open a movie that has exactly the properties we desire, without having to rely on QuickTime to establish some default set of properties that we later need to override. It also allows us to specify properties that cannot be specified using the existing functions. For instance, the constant pitch audio setting (whereby the audio pitch remains constant even when the playback rate of a movie increases or decreases, thus avoiding the infamous "chipmunk" effect when fast-forwarding through a movie) must be set at the time a movie is created, and NewMovieFromProperties is the only movie-opening function that allows us to specify a setting for that property.

In this article, we'll see how to work with NewMovieFromProperties. We'll take a look at the classes of properties that we can pass to it and see how to set movie properties not otherwise settable using the existing NewMovieFrom functions. This topic might seem vaguely familiar to you, as we touched on a very similar programming model when investigating the initWithAttributes:error: method in the QTMovie class in QTKit (see "Back to the Future, Part III" in MacTech, July 2005). In fact, initWithAttributes:error: internally calls NewMovieFromProperties, as you might easily have guessed.

Input Properties

Let's begin by taking a look at the declaration of NewMovieFromProperties. In the Movies.h file shipped with QuickTime 7, we see essentially this:

OSStatus NewMovieFromProperties (
  ItemCount                        inputPropertyCount,
  QTNewMoviePropertyElement*       inputProperties,
  ItemCount                        outputPropertyCount,
  QTNewMoviePropertyElement*       outputProperties,
  Movie *                          theMovie);

As you can see, this function takes as input an array of QTNewMoviePropertyElement structures (inputProperties) and the number of elements in that array (inputPropertyCount). These properties describe how to instantiate the movie. If successful, this function returns a QuickTime movie identifier in the location pointed to by the theMovie parameter. It may also return to the caller a different array of properties (outputProperties), which provide additional information about the newly-created movie. These output properties, for instance, may indicate whether a data reference passed in the inputProperties array was changed during the process of opening the movie. (More on output properties later.)

The QTNewMoviePropertyElement structure is defined like this:

struct QTNewMoviePropertyElement {
  QTPropertyClass               propClass;
  QTPropertyID                  propID;
  ByteCount                     propValueSize;
  QTPropertyValuePtr            propValueAddress;
  OSStatus                      propStatus;
};

The first two fields of this structure are the class and the ID of a movie property; if you have read the previous two QuickTime Toolkit articles, these items should be clear enough. The third and fourth fields indicate the size and location of the value of that property.

For input properties, the final field of the QTNewMoviePropertyElement structure, propStatus, is set by NewMovieFromProperties to a status value that indicates whether the specified property was successfully set on the new movie. In general, the value of this field will be set to 0 (noErr). But occasionally a non-zero result will be returned in that field. For example, if you mistakenly pass in a data value that is not the size that QuickTime is expecting for the class and ID you specify, the value -2184 (kQTPropertyBadValueSizeErr) may be returned in that field. Similarly, if you specify a property that cannot be set, then the value -2191 (kQTPropertyReadOnlyErr) will be returned.

The simplest possible way to call NewMovie FromProperties is to pass in no input properties and to request no output properties, like this:

err = NewMovieFromProperties(0, NULL, 0, NULL, &movie);

This is effectively the same as calling NewMovie with its flags parameter set to 0 -- not particularly useful, but sometimes necessary if you just want to create a new empty movie with all the default characteristics. We're more likely to call NewMovieFromProperties passing in a properties array that at least includes a movie location and some additional properties. Let's see how to do that.

Specifying a Movie Location

The location of a movie's data is specified by adding to the input properties array an element with the kQTPropertyClass_DataLocation class. Currently these property IDs are supported:

enum {
  kQTDataLocationPropertyID_DataReference              = 'dref',
  kQTDataLocationPropertyID_CFStringNativePath         = 'cfnp',
  kQTDataLocationPropertyID_CFStringPosixPath          = 'cfpp',
  kQTDataLocationPropertyID_CFStringHFSPath            = 'cfhp',
  kQTDataLocationPropertyID_CFStringWindowsPath        = 'cfwp',
  kQTDataLocationPropertyID_CFURL                      = 'cfur',
  kQTDataLocationPropertyID_QTDataHandler              = 'qtdh',
  kQTDataLocationPropertyID_Scrap                      = 'scrp',
  kQTDataLocationPropertyID_LegacyMovieResourceHandle  = 'rezh',
  kQTDataLocationPropertyID_MovieUserProc              = 'uspr',
  kQTDataLocationPropertyID_ResourceFork               = 'rfrk',
  kQTDataLocationPropertyID_DataFork                   = 'dfrk'
};

For example -- starting with an easy case -- we can open a new movie that uses data on the scrapbook (or Cocoa pasteboard) by using the kQTDataLocationPropertyID_Scrap ID, as shown in Listing 1.

Listing 1: Loading a movie from the scrapbook/pasteboard

QTNewMoviePropertyElement props[1] = {{0}};
Movie movie = NULL;

props[0].propClass = kQTPropertyClass_DataLocation;
props[0].propID = kQTDataLocationPropertyID_Scrap;
props[0].propValueSize = 0;
props[0].propValueAddress = NULL;

err = NewMovieFromProperties(1, props, 0, NULL, &movie);

Notice that we do not need to assign any non-zero value to the propValueAddress field, since the property ID uniquely identifies the location of the movie data. Listing 1 provides a reasonable approximation of the existing NewMovieFromScrap function.

Listing 2 shows a slightly more interesting example, which opens a movie specified by a URL, in this case a CFURL.

Listing 2: Loading a movie from a URL

QTNewMoviePropertyElement props[1] = {{0}};
Movie movie = NULL;

props[0].propClass = kQTPropertyClass_DataLocation;
props[0].propID = kQTDataLocationPropertyID_CFURL;
props[0].propValueSize = sizeof(CFURLRef);
props[0].propValueAddress = &cfurl;

err = NewMovieFromProperties(1, props, 0, NULL, &movie);

And Listing 3 shows the most general case, where the movie data location is specified by a data reference. In this case, we need to pass the address of a DataReferenceRecord, declared like this:

struct DataReferenceRecord {
  OSType              dataRefType;
  Handle              dataRef;
};

Listing 3: Loading a movie from a URL data reference

QTNewMoviePropertyElement props[1] = {{0}};
DataReferenceRecord dRefRec;
Movie movie = NULL;

dRefRec.dataRefType = URLDataHandlerSubType;
dRefRec.dataRef = url;

props[0].propClass = kQTPropertyClass_DataLocation;
props[0].propID = kQTDataLocationPropertyID_DataReference;
props[0].propValueSize = sizeof(dRefRec);
props[0].propValueAddress = &dRefRec;

err = NewMovieFromProperties(1, props, 0, NULL, &movie);

Specifying Movie Properties

So far, this should all be straightforward: for any particular movie data locator ID, we just need to set the propValueSize and propValueAddress fields appropriately. There should be at most one data locator property in the array we pass to NewMovieFromProperties. But there can also be other kinds of properties, including movie instantiation properties (whose class is kQTPropertyClass_MovieInstantiation) and new movie properties (whose class is kQTPropertyClass_NewMovieProperty). Here are the currently-defined movie instantiation input properties, which govern how QuickTime instantiates a movie:

enum {
  kQTMovieInstantiationPropertyID_DontResolveDataRefs           = 'rdrn',
  kQTMovieInstantiationPropertyID_DontAskUnresolvedDataRefs     = 'aurn',
  kQTMovieInstantiationPropertyID_DontAutoAlternates            = 'aaln',
  kQTMovieInstantiationPropertyID_DontUpdateForeBackPointers    = 'fbpn',
  kQTMovieInstantiationPropertyID_AsyncOK                       = 'asok',
  kQTMovieInstantiationPropertyID_IdleImportOK                  = 'imok',
  kQTMovieInstantiationPropertyID_DontAutoUpdateClock           = 'aucl'
};

And here are the currently defined new movie properties, which provide additional settings for a new movie:

enum {
  kQTNewMoviePropertyID_DefaultDataRef         = 'ddrf',
  kQTNewMoviePropertyID_Active                 = 'actv',        
  kQTNewMoviePropertyID_DontInteractWithUser   = 'intn'
};

These two sets of properties mirror the newMovie flags specifiable as a parameter to the NewMovie and similar functions:

enum {
  newMovieActive                       = 1 << 0,
  newMovieDontResolveDataRefs          = 1 << 1,
  newMovieDontAskUnresolvedDataRefs    = 1 << 2,
  newMovieDontAutoAlternates           = 1 << 3,
  newMovieDontUpdateForeBackPointers   = 1 << 4,
  newMovieDontAutoUpdateClock          = 1 << 5,
  newMovieAsyncOK                      = 1 << 8,
  newMovieIdleImportOK                 = 1 << 10,
  newMovieDontInteractWithUser         = 1 << 11
};

For example, to open a movie specified by a URL so that the movie data loads asynchronously and so that the resulting movie is active, we could execute the code in Listing 4.

Listing 4: Loading a movie from a URL with additional properties

QTNewMoviePropertyElement props[3] = {{0}};
DataReferenceRecord dRefRec;
Movie movie = NULL;
Boolean isActive = true;
Boolean isAsync = true;
long num = 0;

dRefRec.dataRefType = URLDataHandlerSubType;
dRefRec.dataRef = url;

props[0].propClass = kQTPropertyClass_DataLocation;
props[0].propID = kQTDataLocationPropertyID_DataReference;
props[0].propValueSize = sizeof(dRefRec);
props[0].propValueAddress = &dRefRec;
num++;

props[1].propClass = kQTPropertyClass_MovieInstantiation;
props[1].propID = kQTMovieInstantiationPropertyID_AsyncOK;
props[1].propValueSize = sizeof(isAsync);
props[1].propValueAddress = &isAsync;
num++;

props[2].propClass = kQTPropertyClass_NewMovieProperty;
props[2].propID = kQTNewMoviePropertyID_Active;
props[2].propValueSize = sizeof(isActive);
props[2].propValueAddress = &isActive;
num++;

err = NewMovieFromProperties(num, props, 0, NULL, &movie);

Output Properties

As noted earlier, NewMovieFromProperties can also return a set of properties to the caller, which indicate additional information about the newly-opened movie. Currently there are two such output properties:

kQTMovieResourceLocatorPropertyID_LegacyResID
kQTMovieResourceLocatorPropertyID_LegacyResName

These indicate the resource ID of the movie and the name of the movie resource. The resource name is generally not terribly useful, but the resource ID can be useful in determining whether the movie atom was loaded from the file's data fork (returned value is -1) or the resource fork (returned value is greater than 0), or whether there was no movie atom in the storage container (returned value is 0).

We can obtain an output property by passing in a second array of QTNewMoviePropertyElement structures, as shown in Listing 5.

Listing 5: Getting an output property

QTNewMoviePropertyElement props[3] = {{0}};
QTNewMoviePropertyElement outProps[1] = {{0}};
Movie movie = NULL;
short resID = 0;
long num = 0;

// set-up of input properties omitted

outProps[0].propClass = 
                  kQTPropertyClass_MovieResourceLocator;
outProps[0].propID = 
                  kQTMovieResourceLocatorPropertyID_LegacyResID;
outProps[0].propValueSize = sizeof(resID);
outProps[0].propValueAddress = &resID;

err = NewMovieFromProperties(num, props, 1, outProps, 
                  &movie);

On successful completion of this code, the local variable resID will contain the resource ID of the movie resource.

Conclusion

In this article, we've learned how to use the NewMovieFromProperties function introduced in QuickTime 7 as a replacement for the array of existing NewMovieFrom functions. We've seen how to specify the location of the movie data and how to set default properties on the new movie. We've also seen how to get values of certain properties back from NewMovieFromProperties.

In the next several articles, we'll continue investigating NewMovieFromProperties. In particular, we'll take a look at the properties associated with the kQTPropertyClass_Context property class, which allows us to set media context properties of a movie. We use these properties to create movies that render into a visual context (such as an OpenGL texture buffer) or to a particular audio device.


Tim Monroe is a member of the QuickTime engineering team at Apple. You can contact him at monroe@mactech.com. The views expressed here are not necessarily shared by his employer.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Can PokeMatch help you find love with Po...
The unofficial Pokemon GO companion app space has exploded almost as fast as the game itself over the last few weeks. Aspiring app developers, many of them working solo, have given us apps that locate Pokemon, keep track of the server status, and... | Read more »
How to get started with Prisma
If there's one thing people like to do more than taking pictures with their smartphones, it's tinkering with those photos in some way. Numerous apps have sprung up over the last several years that allow you to use filters and special effects to... | Read more »
6 Pokemon GO updates you can expect, acc...
Pokemon GO had a scheduled appearance at this year's San Diego Comic-Con for a while, but it was only relatively close to the show that it was upgraded to a spot in Hall H. That's the biggest venue at SDCC, one usually reserved for the largest... | Read more »
How to evolve Eevee in Pokemon GO
By now, almost everyone should be hip to how to evolve Pokemon in Pokemon GO (and if not, there's a guide for that). Just gather enough candy of the appropriate type, feed them all to the Pokemon, and evolution happens. It's a miracle that would... | Read more »
CSR Racing 2: Guide to all game modes
It might not seem like there are all that many ways to go fast in a straight line, but CSR Racing 2 begs to differ. [Read more] | Read more »
Bulb Boy (Games)
Bulb Boy 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Multi-award winning 2D point & click horror adventure about a boy with a glowing head. | Read more »
5 top free emoji keyboard apps
If we're not at peak emoji yet as a society, it feels like we definitely should be. The emoji concept has gone far beyond what anyone in Japan could have envisioned when the people there unleashed it on an unsuspecting world, but the West has... | Read more »
How to unlock more characters in Disney...
One of the big charms of Disney Emoji Blitz is seeing a wide variety of beloved Disney and Pixar characters transformed into smiling emojis. Even someone like the sneaky Randall from Monsters Inc., who probably never cracked a smile on film, is... | Read more »
Cubway (Games)
Cubway 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Cubway is a journey with an abstract story of lifecycle of rebirth, called Samsara. Guide the cube through the long way full of dangers... | Read more »
Colorcube (Games)
Colorcube 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Turn pieces and blend colours in this minimal yet visually stunning puzzler.Over 200 handcrafted and challenging levels. Features... | Read more »

Price Scanner via MacPrices.net

Clearance 12-inch Retina MacBooks, Apple refu...
Apple has Certified Refurbished 2015 12″ Retina MacBooks available starting at $929. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The following... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina MacBook Pros on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro: $1199 $100 off MSRP - 13″ 2.7GHz/... Read more
13-inch 1.6GHz/128GB MacBook Air on sale for...
Amazon has the 13″ 1.6GHz/128GB MacBook Air on sale for $200 off MSRP for a limited time. Shipping is free: - 13″ 1.6GHz/128GB MacBook Air (sku MMGF2LL/A): $799.99 $200 off MSRP Their price is the... Read more
13-inch 1.6GHz/256GB MacBook Air on sale for...
Amazon has the 13″ 1.6GHz/256GB MacBook Air on sale for $200 off MSRP for a limited time. Shipping is free: - 13″ 1.6GHz/256GB MacBook Air (sku MMGG2LL/A): $999.99 $200 off MSRP Their price is the... Read more
Free iOS Business App notably* Helps Service...
PayStudio Inc. has introduced their new business app notably* 1.0, developed for iPhone and iPod touch. notably* was specifically developed to help service and trade professionals go digital and... Read more
27-inch iMacs on sale for $200 off MSRP
Amazon has 27″ iMacs on sale for $200 off MSRP including free shipping: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $1799.99 $200 off MSRP - 27″ 3.2GHz/1TB HD iMac 5K... Read more
Mac Pros on sale for $200 off MSRP
B&H Photo has Mac Pros on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3799, $200... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
13-inch 2.5GHz MacBook Pro (Apple refurbished...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros... Read more

Jobs Board

*Apple* Retail - Multiple Positions, Willow...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Evangelist - JAMF Software (United S...
The Apple Evangelist is responsible for building and cultivating strategic relationships with Apple 's small and mid-market business development field teams. This Read more
*Apple* Solutions Consultant - APPLE (United...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
*Apple* Professional Learning Specialist - A...
Job Summary The Apple Professional Learning Specialist is a full-time position for one year with Apple in the Phoenix, AZ area. This position requires a high Read more
*Apple* Picker - Apple Hill Orchard (United...
Apple Hill Orchard, Co. Rte. 21,Whitehall, NY 9/7/16-10/228/16. Pick fresh market or processing apples Productivity of 60 boxes and 80 boxes processing fruit per Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.