I need to write a component that should be called any time an
application wants to play video through QuickTime so it can check
some data in the movie file (in media "Initialize") and either modify
it before playing or let QT do its things as usual.
I thought of creating a derived media handler to override the Apple
Video Media Handler ('mhlr'/'vide') which seems to be used for every
kind of video files I must check. I decided to capture this media
handler so that each time an application opens a video movie, my
component is called first. It can then check if it must act on the
media or not. If not, it just calls the original media handler.
Otherwise it edits the data (in the idle function) before drawing it
with the regular codec.
So far my component appears to register properly, with the intended
flags, type, subtype and manufacturer. I can verify that the captured
media handler is removed from the list of available media handlers.
Also, I can verify that the Open and Close functions are called
properly and the memory allocated, set and disposed as I want. But
that's all. At the moment I would like to use the "Idle" and
"Initialize" functions in my component and delegating all the others
but they are never called. For testing, I added SetDimensions and
SetMatrix too but they are not called either when I changed the size
of the window playing the movie.
I looked carefully at the Apple sample codes, but they are all for
codecs or importers/exporters. I found 3 older examples of media
handlers but they are not directly applicable because many things
seemed to have changed (in particular the use of
ComponentDispatchHelper.c.
So I guess my question is twofold:
1. Is my approach correct or is it too dangerous or forbidden to
override this kind of "low level" component?
2. Why only "Open" and "Close" are called and not "Initialize" and
"Idle"?
(by the way, I could not get the "Register" function to be called
even after setting the corresponding flag in the component resource;
I no longer use this flag now anyway, since I read it is not
recommended on Mac OS X: <http://developer.apple.com/qa/qa2001/
qa1192.html>)
Sorry for the long post...
I've spent the last few days trying to make this work but to no
avail. I've read everything I could find on the subject in the
archives, the sample codes and elsewhere thanks to Google, but it has
only got me started. The most interesting articles on media handlers
and component capture I could find are more than 10 years old so
things have changed in some areas.
// Type definitions
// Instance storage (passed by the Component Manager)
typedef struct MYMH_Globals {
// component stuff
ComponentInstance fDelegate; // the base component we are
delegating to
ComponentInstance fSelf; // ourself
ComponentInstance fParent; // our parent, if we are targeted by
another media handler
... (allocate the instance memory (myStorage) then tell the Comp. Mgr)
(*myStorage)->fSelf = theSelf;
SetComponentInstanceStorage(theSelf, (Handle)myStorage);
... (allocate the component memory (mySharedStorage) if needed)
... (get our component rather than the instance: myComponent)
... (get the component to be captured: delegateComponent)
// Capture the base video media handler
mySharedStorage->delegateComponent = CaptureComponent
(delegateComponent, myComponent);
if (!mySharedStorage->delegateComponent) return (componentNotCaptured);
// open the base video media handler component and target it
result = OpenAComponent( mySharedStorage->delegateComponent, &
((*myStorage)->fDelegate) );
if (result == noErr) {
result = ComponentSetTarget((*myStorage)->fDelegate, (*myStorage)-
>fSelf);
//if (result == badComponentSelector) SysBeep(60); // testing...
}
(mySharedStorage->instanceCount)++;
(*myStorage)->fParent = theSelf;
PASCAL_RTN ComponentResult MYMH_Target (MYMH_GlobalsHdl storage,
ComponentInstance theTarget)
{
// remember who is at the top of our calling chain
(**storage).fParent = theTarget;
if ((**storage).fDelegate)
// inform the base media handler of the change
ComponentSetTarget((**storage).fDelegate, theTarget);
ComponentComment ("Count of selectors in range 0")
ComponentSelectorOffset (6)
//ComponentSelectorOffset (7) // if we add Unregister call, the
count is 7
ComponentComment ("Last selector range of this component")
ComponentRangeCount (6)
ComponentComment ("Size of each selector range in bits")
ComponentRangeShift (8)
ComponentRangeMask (FF)
ComponentComment ("Core Selector Range")
ComponentRangeBegin (0)
//StdComponentCall (Unregister)
StdComponentCall (Target)
StdComponentCall (Register) // No change if I use ComponentError
StdComponentCall (Version) // instead of StdComponentCall for
StdComponentCall (CanDo) // CanDo or Register
StdComponentCall (Close)
StdComponentCall (Open)
ComponentRangeEnd (0)
resource 'thng' (kMYMH_ComponentResID, kMYMH_Name, purgeable) {
kMYMH_ComponentType, // component type
kMYMH_MediaType, // component subtype
kMYMH_ComponentManufacturer, // component manufacturer
0, // component flags
kAnyComponentFlagsMask, // component flags mask
0, // no 68K code use componentHasMultiplePlatforms
0, // no 68K code
'STR ', // component name resource type
kMYMH_NameStringResID, // component name resource ID
'STR ', // component info resource type
kMYMH_InfoStringResID, // component info resource ID
0, // component icon resource type
0, // component icon resource ID
kMYMH_Version,
componentDoAutoVersion | componentHasMultiplePlatforms,
0, // Resource ID of Icon Family
{
#if TARGET_OS_MAC
#if TARGET_REZ_CARBON_MACHO
#if !(TARGET_REZ_MAC_PPC || TARGET_REZ_MAC_X86)
#error "Platform architecture not defined!"
#endif
#if TARGET_REZ_MAC_PPC
0x10000000, // Flags
'dlle', // Code Resource type - Entry point
kMYMH_ComponentResID, // ID of 'mhlr' resource
platformPowerPCNativeEntryPoint // PowerPC-based Macintosh
#endif
#if TARGET_REZ_MAC_X86
0, // Flags
'dlle', // Code Resource type - Entry point
kMYMH_ComponentResID, // ID of 'dlle' resource
platformIA32NativeEntryPoint // Intel-based Macintosh
#endif
#else
#error "TARGET_REZ_CARBON_MACHO should be defined."
#endif
#elif TARGET_OS_WIN32
#if TARGET_REZ_WIN32
0,
'dlle',
kMYMH_ComponentResID,
platformWin32
#else
#error "TARGET_REZ_WIN32 should be defined."
#endif
#else
#error "I have no idea what you're trying to do!"
#endif
}
};
...
#if TARGET_REZ_CARBON_MACHO || TARGET_REZ_WIN32
// Code Entry Point for Mach-O and Windows
resource 'dlle' (kMYMH_ComponentResID, kMYMH_Name) {
"MYMH_ComponentDispatch"
};
#endif
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