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Technote 1035

MARCH 1996

You should be thoroughly familiar with the QuickTime Movie Toolbox, as documented in Inside Macintosh: QuickTime. In particular, knowledge of the sections on creating a movie and working with media samples is essential for making use of the information in this document.

Note:

Although this file format will be supported in future versions of QuickTime VR, be aware that the panorama movie file format will change significantly in the next release.

• About the Panorama Movie File Format
  
• QuickTime VR Panorama Movie Authoring
  
• Summary
  

In a single node movie the panorama track contains one media sample. In a multinode panorama, the panorama track contains one sample for each node in the movie. Data in each sample contain information about the panoramic image for the particular node. The scene track contains the panoramic image, usually multiple samples comprising the diced frames of the panorama for a particular node.

When the panorama needs to be imaged, the video samples are decompressed into an offscreen buffer, reconstructing the original uncorrected panoramic image. Based on the current pan, tilt, and zoom angle, a portion of the uncorrected image is copied and partially corrected (1D correction) to another offscreen buffer, whose size is the same as the display window. Then the contents of that buffer are copied to the screen, going through the final correction phase (2D correction). If circumstances (such as a non-rectangular clipped view) do not allow writing directly to the screen, then a second offscreen correction buffer is used and the image is then copied to the screen. If the imaging update mode is set to partial or no correction, then the corresponding correction steps are skipped.

QuickTime VR Panorama Movie Authoring

Two things to keep in mind:

• The QuickTime VR components must be registered when you are authoring a QuickTime VR movie. If the components are not registered, NewTrackMedia will fail when you try to create media for the panorama track.

• QuickTime VR 1.0 requires that QuickTime 2.0 or greater be installed in your system.

The Movie File

Also, as with any QuickTime file that is intended to be played on both platforms, a data fork version of the file should be created using the FlattenMovie Movie Toolbox call with the flattenAddMovieToDataFork flag set.

Movie Controller User Data

	UserData uDat;
	OSType controllerSubType = 'STpn';
	uDat = GetMovieUserData(newMovie);
	SetUserDataItem(uDat, &controllerSubType, 
		sizeof(controllerSubType), 'ctyp', 1);

The Scene and Hot Spot Tracks

You can optionally store a low resolution version of the panoramic image in a video track called the low resolution scene track. If the low resolution scene track exists and there is not enough memory to use the normal scene track, then QuickTime VR uses the low resolution scene track. The low resolution track contains diced frames just like the higher resolution track, but the reconstructed panoramic image is half the height and half the width of the higher resolution version. The number of diced frames for the low resolution scene track is usually half that of the scene track.

The hot spot track is another optional video track that contains a parallel panorama, with colored regions corresponding to hot spots in the scene track's panorama. The hot spot panoramic image must be 8 bits deep. Each diced frame of the hot spot panoramic image must be compressed with a lossless compressor such as QuickTime's Graphics compressor. The dimensions of the hot spot panoramic image is usually the same as that of the scene track's panoramic image, but it is not required. The dimensions must, however, have the same aspect ratio as the scene track's panoramic image.

As with the scene track, the panoramic images corresponding to the low resolution scene track and the hot spot track must be rotated 90deg. counterclockwise.

The Panorama Track

Each sample in the panorama track corresponds to one node in the scene. Panorama track samples with similar characteristics share a sample description of type PanoramaDescription. This data structure contains data that specifies the track IDs of the scene and hot spot tracks. It also contains information about how the panoramic image has been diced.

Each individual panorama track sample contains data about one node. This includes default view angles, pan and zoom constraints, and hot spot information.

The format of the media info, panorama description, and panorama samples are described in the following sections. Figure 1 illustrates how a scene track is created.

Figure 1 Creating the Scene Track

Note:

In the following data structure descriptions, here are the sizes of the standard Macintosh data types used:

Type		bit size
long			32 
unsigned long		32
short			16
unsigned short		16
Fixed			32
OSType			32
Str31			256
TimeValue		32
Rect			64

The structures all use Macintosh 68K alignment. To ensure Mac 68K alignment, place this pragma statment in front of all data structures:

#pragma options align = mac68k

The Media Info Data

MediaGetMediaInfo is defined in the header file MediaHandlers.h and documented in the Derived Media Handler Components section of Inside Macintosh: QuickTime Components, although again, it is documented from the point of view of the media handler implementor. You pass a handle to the PanoMediaInfo structure when you call MediaGetMediaInfo. QuickTime VR will make a copy of the data. You are responsible for disposing of your copy of the handle.

struct PanoMediaInfo {
	long		size;		// the size of the entire media info
	OSType		type;		// must be 'pInf'

	Str31		name;		// the name of the scene
	unsigned long	defNodeID;	// the node to display initially
	Fixed		defZoom;	// the default zoom for all nodes
	long		reserved;	// must be zero

	short		pad;		// must be zero
	short		numEntries;	// the number of nodes in the scene
	IDTableEntry	idToTime[1];	// table mapping node IDs to movie time
};

struct IDTableEntry {
	unsigned long	nodeID;
	TimeValue	time;
};

The following code snippet adds the media info for a two node scene with node IDs 6 and 9.

	PanoMediaInfo **mediaInfoH;
	long numNodes = 2;
	mediaInfoH = (PanoMediaInfo **) NewHandleClear(sizeof(PanoMediaInfo)
			+ (numNodes-1)*sizeof(IDTableEntry));
	(*mediaInfoH )->size = GetHandleSize((Handle) mediaInfoH );
	(*mediaInfoH )->type = 'pInf';
	(*mediaInfoH )->defNodeID = 6;
	(*mediaInfoH )->defZoom = 65L << 16;
	(*mediaInfoH )->numEntries = numNodes;
	(*mediaInfoH )->idToTime[0].nodeID = 6;
	(*mediaInfoH )->idToTime[0].time = 0;
	(*mediaInfoH )->idToTime[1].nodeID = 9;
	(*mediaInfoH )->idToTime[1].time = 7200;
	MediaGetMediaInfo(panoMediaHandler, (Handle)mediaInfoH); 
				// Yes, that's Get, not Set!
	DisposeHandle((Handle) mediaInfoH);

The Panorama Track's Sample Description

struct PanoramaDescription {
	long	size;			// total size of the PanoramaDescription
	long	type;			// must be 'pano'

	long	reserved1;		// must be zero
	long	reserved2;		// must be zero

	short	majorVersion;		// must be zero
	short	minorVersion;		// must be zero

	long	sceneTrackID;		// ID of video track that contains
					  panoramic scene
	long	loResSceneTrackID;	// ID of video track that contains low
					  res panoramic scene
	long	reserved3[6];		// must be zero
	long	hotSpotTrackID;		// ID of video track that contains
					  hotspot image
	long	reserved4[9];		// must be zero

	Fixed	hPanStart;		// horizontal pan range start angle
					  (e.g. 0)
	Fixed	hPanEnd;		// horizontal pan range end angle 
					  (e.g. 360)
	Fixed	vPanTop;		// vertical pan range top angle
					  (e.g. 42.5)
	Fixed	vPanBottom;		// vertical pan range bottom angle 
					  (e.g. -42.5)
	Fixed	minimumZoom;		// minimum zoom angle (e.g. 5; use 0 for
					  default)
	Fixed	maximumZoom;		// maximum zoom angle (e.g. 65; use 0
					  for default)

	// Info for highest res version of scene track
	long	sceneSizeX;		// pixel width of the panorama (e.g. 768)
	long	sceneSizeY;		// pixel height of the panorama (e.g.
					  2496)
	long	numFrames;		// number of diced frames (e.g. 24)
	short	reserved5;		// must be zero
	short	sceneNumFramesX;	// diced frames wide (e.g. 1)
	short	sceneNumFramesY;	// diced frames high (e.g. 24)
	short	sceneColorDepth;	// bit depth of the scene track (e.g. 32)

	// Info for highest res version of hotSpot track
	long	hotSpotSizeX;		// pixel width of the hot spot panorama
					  (e.g. 768)
	long	hotSpotSizeY;		// pixel height of the hot spot panorama
					  (e.g. 2496)
	short	reserved6;		// must be zero
	short	hotSpotNumFramesX;	// diced frames wide (e.g. 1)
	short	hotSpotNumFramesY;	// diced frames high (e.g. 24)
	short	hotSpotColorDepth;	// must be 8

};

Note:

hPan, vPan, and zoom angles will be called pan, tilt, and field of view in future versions of QuickTime VR.

The Panorama Track Samples

Note:

This file format pre-dates the QuickTime 2.1 Atom Data routines and is not compatible with them.

The panorama header atom (type 'pHdr') contains information about the node itself, such as its node ID, the default viewing angles, and panning and zooming constraints specific to this node. If there are no constraints specific to this node, then 0 should be used for the min and max values. The nameStrOffset and commentStrOffset fields (in this and other atoms) contain offsets into the string table atom.

struct PanoSampleHeaderAtom {
	long		size;
	OSType		type;			// must be 'pHdr'

	unsigned long	nodeID;			// corresponds to a node ID in the
						  idToTime table above
	Fixed		defHPan;		// default horizontal pan angle when
						  displaying this node
	Fixed		defVPan;		// default vertical pan angle when
						  displaying this node
	Fixed		defZoom;		// default zoom angle when displaying
						  this node

	// constraints for this node; use zero for default
	Fixed		minHPan;	
	Fixed		minVPan;
	Fixed		minZoom;
	Fixed		maxHPan;
	Fixed		maxVPan;
	Fixed		maxZoom;

	long		reserved1;		// must be zero
	long		reserved2;		// must be zero
	long		nameStrOffset;		// offset into string table atom
	long		commentStrOffset;	// offset into string table atom
};

struct StringTableAtom {
	long	size;
	OSType	type;			// must be 'strT'
	char	bunchOstrings[1];	// concatenated Pascal strings
};

struct HotSpotTableAtom {
	long		size;
	OSType		type;		// must be 'pHot'

	short		pad;		// must be zero
	short		numHotSpots;
	HotSpot		hotSpots[1];
};

struct HotSpot {
	unsigned short	hotSpotID;	// the ID of this hot spot
	short		reserved1;	// must be zero
	OSType		type;		// the hot spot type (e.g. 'link',
					  'navg', etc)
	unsigned long	typeData;	// for link and navg, the ID in the link
					  and navg table

	// canonical view for this hot spot
	Fixed		viewHPan;
	Fixed		viewVPan;
	Fixed		viewZoom;
	
	Rect		hotSpotRect;	// bounding rectangle of the hot spot in
					  the panorama

	long		mouseOverCursorID;
	long		mouseDownCursorID;
	long		mouseUpCursorID;
	long		reserved2;		// must be zero
	long		nameStrOffset;		// offset into string table atom
	long		commentStrOffset;	// offset into string table atom
};

struct LinkTableAtom {
	long		size;
	OSType		type;			// must be 'pLnk'
	
	short		pad;			// must be zero
	short		numLinks;
	PanoLink		links[1];
};

struct PanoLink {
	unsigned short	linkID;			// ID referred to by the typeData
						  field in the hot spot atom
	short		reserved1;		// must be zero
	long		reserved2;		// must be zero
	long		reserved3;		// must be zero
	unsigned long	toNodeID;		// the node id of the destination
						  node
	long		reserved4[3];		// must be zero
	Fixed		toHPan;			// horizontal pan angle to set at
						  the destination node
	Fixed		toVPan;			// vertical pan angle to set at the
				 		  destination node
	Fixed		toZoom;			// zoom angle to set at the
						  destination node
	long		reserved5;		// must be zero
	long		reserved6;		// must be zero
	long		nameStrOffset;		// offset into string table atom
	long		commentStrOffset;	// offset into string table atom
};

Note:

Navigable Object movies are called simply Object movies in future versions of QuickTime VR; the term "navigable" is going away.

struct NavgTableAtom {
	long		size;
	OSType		type;			// must be 'pNav'
	
	short		pad;			// must be zero
	short		numObjects;
	NavgObject	objects[1];		//  navigable objects
};

struct NavgObject {
	unsigned short	objID;			// ID referred to by the typeData
						  field in the hot spot atom
	short		reserved1;		// must be zero
	long		reserved2;		// must be zero

	// Info for Navigable Movie Controller
	Fixed		navgHPan;		// the object's orientation in the
						  scene
	Fixed		navgVPan;
	Fixed		navgZoom;
	Rect		zoomRect;		// starting rect for zoom out
						  transition

	long		reserved3;		// must be zero
	long		nameStrOffset;		// offset into string table atom
	long		commentStrOffset;	// offset into string table atom
};

Track Layout

Figure 2 Single Node Panorama File

Figure 3 Multinode Panorama File

The video samples corresponding to the low resolution scene track, if one exists, are also located at the same time and total duration as the panorama sample. Likewise, the hot spot track, if it exists, has its samples for a particular node located at the same time and total duration as the panorama sample. (Figure 4).

Figure 4 Multinode Panorama File with Low-Res Scene Track and Hot Spot Track

In a panorama movie file the scene track, low resolution scene track, and hot spot track are all disabled. Only the panorama track is enabled. The track dimensions and track matrix of the panorama track determine the rectangle returned by the GetMovieBox call.

Summary

Authoring a multi-node panorama file with hot spots is a complex process. Make sure you verify the resulting file using QTVRPlayer.

• Inside Macintosh: QuickTime
• Inside Macintosh: QuickTime Components
• Technote 1036, "QuickTime VR 1.0 Object Movie File Format"