### Interleaved Media Data Layout Example

Source: https://developer.apple.com/documentation/quicktime-file-format/using_quicktime_files_and_media_layouts

Illustrates the optimal ordering of hint track (H) samples and media (A for audio, V for visual) samples within a QuickTime file to minimize file seeks during playback. Hint samples must precede the media data they reference.

```text
H0 A0 H1 V1 H2 V2 H3 A1 H4 A2 V3 H5 V4
```

--------------------------------

### Insert Second Atom Before First Atom

Source: https://developer.apple.com/documentation/quicktime-file-format/creating_new_atoms

This example shows how to insert a second child atom into an existing container. By specifying an index of 1, the new atom is inserted before the first atom, shifting the index of the first atom.

```c
QTAtom secondAtom;

FailOSErr (QTInsertChild (container, kParentAtomIsContainer, 'abcd',
    2000, 1, 0, nil, &secondAtom));
```

--------------------------------

### Implementing a QTVR Intercept Procedure

Source: https://developer.apple.com/documentation/quicktime-file-format/adding_custom_atoms_in_a_quicktime_vr_movie

This C code defines an intercept procedure for handling custom hot spot clicks in a QuickTime VR movie. It checks for a specific custom hot spot type, extracts custom data, and processes it. Install this procedure when opening the movie and uninstall it when no longer needed.

```c
QTVRInterceptProc MyProc = NewQTVRInterceptProc (MyHotSpot);
QTVRInstallInterceptProc (qtvr, kQTVRTriggerHotSpotSelector, myProc,  0, 0);

pascal void MyHotSpot (QTVRInstance qtvr, QTVRInterceptPtr qtvrMsg,
                        SInt32 refCon, Boolean *cancel)
{
    UInt32 hotSpotID = (UInt32) qtvrMsg->parameter[0];
    QTAtomContainer nodeInfo =
            (QTAtomContainer) qtvrMsg->parameter[1];
    QTAtom hotSpotAtom = (QTAtom) qtvrMsg->parameter[2];
    OSType hotSpotType;
    CustomData myCustomData;
    QTAtom myAtom;

    QTVRGetHotSpotType (qtvr, hotSpotID, &hotSpotType);
    if (hotSpotType != kMyAtomType) return;

    // It's our type of hot spot - don't let anyone else handle  it
    *cancel = true;

    // Find our custom atom
    myAtom = QTFindChildByID (nodeInfo, hotSpotAtom, kMyAtomType,  1, nil);
    if (myAtom != 0) {
        OSErr err;
        // Copy the custom data into our structure
        err = QTCopyAtomDataToPtr (nodeInfo, myAtom, false,
                        sizeof(CustomData), &myCustomData, nil);
        if (err == noErr)
            // Do something with it
            DoMyHotSpotStuff (hotSpotID, &myCustomData);
    }
}
```

--------------------------------

### Hypertext Range Definition Atoms

Source: https://developer.apple.com/documentation/quicktime-file-format/hypertext_and_wired_text

Defines the start and end offsets for hypertext within a text stream. These are unsigned long integers.

```text
kRangeStart         strt // unsigned long
kRangeEnd           end  // unsigned long
```

--------------------------------

### Create a New QTAtomContainer for Input Map

Source: https://developer.apple.com/documentation/quicktime-file-format/creating_an_input_map

Initializes a new QuickTime atom container to hold the input map. This is the first step in building an input map.

```c
QTNewAtomContainer(&inputMap);
```

--------------------------------

### Remove all atoms from containers

Source: https://developer.apple.com/documentation/quicktime-file-format/removing_atoms_from_an_atom_container

Use `QTRemoveChildren` with `kParentAtomIsContainer` to clear all atoms from an atom container. This is useful for resetting containers before adding new data, as shown in the example for updating sprite animations.

```c
QTAtomContainer sample, spriteData;

// ...
// Add the sprite key sample.
// ...

// Add override samples to make the sprites spin and move.
for (i = 1; i <= kNumOverrideSamples; i++)
{
    QTRemoveChildren (sample, kParentAtomIsContainer);
    QTRemoveChildren (spriteData, kParentAtomIsContainer);

    // ...
    // Update the sprite:
    // - Update the imageIndex.
    // - Update the location.
    // ...

    // Add atoms to spriteData atom container.
    SetSpriteData (spriteData, &location, nil, nil, &imageIndex);

    // Add the spriteData atom container to sample.
    err = AddSpriteToSample (sample, spriteData, 2);

    // ...
    // Update other sprites.
    // ...

    // Add the sample to the media.
    err = AddSpriteSampleToMedia (newMedia, sample,
        kSpriteMediaFrameDuration, false);
}
```

--------------------------------

### Update Media Input Map for Modifier Track

Source: https://developer.apple.com/documentation/quicktime-file-format/creating_movies_with_modifier_tracks

After adding a track reference, update the receiving track's media input map to describe how the modifier data should be interpreted. This example sets the input type to kTrackModifierTypeClip.

```c
QTAtomContainer inputMap;
QTAtom inputAtom;
OSType inputType;


Media aVideoMedia = GetTrackMedia(aVideoTrack);
GetMediaInputMap (aVideoMedia, &inputMap);

QTInsertChild(inputMap, kParentAtomIsContainer, kTrackModifierInput,
        addedIndex, 0,0, nil, &inputAtom);

inputType = kTrackModifierTypeClip;
QTInsertChild (inputMap, inputAtom, kTrackModifierType, 1, 0,
        sizeof(inputType), &inputType, nil);

SetMediaInputMap(aVideoMedia, inputMap);
QTDisposeAtomContainer(inputMap);
```

--------------------------------

### Create Atom Container for QTVR Import Preview

Source: https://developer.apple.com/documentation/quicktime-file-format/sample_atom_container_for_the_qtvr_flattener

Use this code to create an atom container and add atoms that indicate an import preview file for the QTVR flattener. Ensure `previewSpec` is defined elsewhere.

```c
Boolean yes = true;
QTAtomContainer exportData;
QTAtom parent;
err = QTNewAtomContainer(&exportData);
// create a parent for the other settings atoms
err = QTInsertChild (exportData, kParentAtomIsContainer,
            QTVRFlattenerParentAtomType, 1, 0, 0, nil, &parent);
// Add child atom to indicate we want to import the preview from  a file
err = QTInsertChild (exportData, parent, QTVRImportPreviewAtomType,  1, 0,
            sizeof (yes), &yes, nil);
// Add child atom to tell which file to import
err = QTInsertChild (exportData, parent, QTVRImportSpecAtomType,  1, 0,
            sizeof (previewSpec), &previewSpec, nil);
// Tell the export component
MovieExportSetSettingsFromAtomContainer (qtvrExport, exportData);
```

--------------------------------

### Insert New Parent Atom and Then Its Children

Source: https://developer.apple.com/documentation/quicktime-file-format/copying_existing_atoms

First, insert a new parent atom into a container using QTInsertChild. Then, use QTInsertChildren to insert another container as children of the newly created parent atom. Error checking is done via FailOSErr.

```c
FailOSErr (QTInsertChild (theSample, kParentAtomIsContainer,
    kSpriteAtomType, spriteID, 0, 0, nil, &newSpriteAtom));

FailOSErr (QTInsertChildren (theSample, newSpriteAtom, theSprite));

```

--------------------------------

### QuickTime VR Sample Description Structure

Source: https://developer.apple.com/documentation/quicktime-file-format/quicktime_vr_sample_description

Defines the structure for QuickTime VR sample descriptions. This structure is required by QuickTime for the first several bytes of sample descriptions.

```c
typedef struct QTVRSampleDescription {
    UInt32                              size;
    UInt32                              type;
    UInt32                              reserved1;
    UInt16                              reserved2;
    UInt16                              dataRefIndex;
    UInt32                              data;
} QTVRSampleDescription, *QTVRSampleDescriptionPtr, **QTVRSampleDescriptionHandle;

```

--------------------------------

### Adjust Display Offsets for Composition

Source: https://developer.apple.com/documentation/quicktime-file-format/using_composition_offset_and_composition_shift_least_greatest_atoms

Write a composition offset table atom by adjusting each display offset. Subtract the calculated composition offset shift from the original display offset to get the new composition offset. If a composition shift least greatest atom is absent, assume the shift is zero.

```pseudocode
compositionOffset[n] = displayOffset[n] - compositionOffsetToDisplayOffsetShift;
```

--------------------------------

### QuickTime Streaming Media Sample Description Structure

Source: https://developer.apple.com/documentation/quicktime-file-format/streaming_media

Defines the structure for interpreting streaming media data in QuickTime. The 'dataFormat' field specifies how to interpret the sample, with 'rtsp' and 'sdp ' being currently defined values.

```c
struct QTSSampleDescription {
    long                            descSize;
    long                            dataFormat;
    long                            resvd1;     /* set to 0*/
    short                           resvd2;     /* set to 0*/
    short                           dataRefIndex;
    UInt32                          version;
    UInt32                          resvd3;     /* set to 0*/
    SInt32                          flags;
                                                /* qt atoms follow:*/
                                    /* long size, long type, some  data*/
                                                /* repeat as necessary*/
};
typedef struct QTSSampleDescription     QTSSampleDescription;
```

--------------------------------

### Create an Atom Container

Source: https://developer.apple.com/documentation/quicktime-file-format/creating_copying_and_disposing_of_atom_containers

Call `QTNewAtomContainer` to create a new atom container. Ensure you have a valid `OSErr` variable to capture potential errors.

```c
QTAtomContainer spriteData;
OSErr err
// Create an atom container to hold a sprite’s data.
err=QTNewAtomContainer (&spriteData);
```