I'm working on some face detection code on OSX Mavericks and I'm trying to take advantage of the newish (as of 10.8) face tracking across multiple stills functionality that CIDetector offers.
I have basic face detection working fine, like so:
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CIImage *image = [CIImage imageWithCVImageBuffer:imageBuffer];
CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace
context:nil
options:#{ CIDetectorAccuracy : CIDetectorAccuracyHigh,
CIDetectorTracking : #YES
}];
NSArray *features = [faceDetector featuresInImage:image];
for ( CIFaceFeature *feature in features ) {
if (feature.hasTrackingID) {
NSLog(#"tracking id: %#", #(feature.trackingID));
}
}
}
The features list does get populated correctly but that trackingID never seems to be present.
Has anyone gotten this working on Mavericks? It fails the same way on Mountain Lion.
I have seen a similar question here (CIFaceFeature trackingID is always coming same for multiple faces) but I didn't learn anything new there.
For what it's worth it does seem to function correctly on iOS.
I looked at this code again and the answer turned out to be pretty obvious: I was constantly re-initializing the CIDetector, which was bad for performance and also had the consequence of resetting its internal tracking data each frame. So the first time a face was detected was always the first time a face was detected for that particular CIDetector instance.
Also, CIDetector warns about this in the docs:
"This class can maintain many state variables that can impact performance. So for best performance, reuse CIDetector instances instead of creating new ones.", from https://developer.apple.com/library/mac/documentation/CoreImage/Reference/CIDetector_Ref/Reference/Reference.html.
Related
My CMPedometer is not running.
The code before it and after it gets run, but it itself does not work.
I get no warning or exception.
I'm testing it on a real 5s.
I've tried both querydata and startpedometerupdates.
I am importing core motion and the library is linked.
Any help?
if ([CMPedometer isStepCountingAvailable] == YES)
{
CMPedometer *cmped;
[cmped queryPedometerDataFromDate:start toDate:[NSDate date] withHandler:^(CMPedometerData *pedometerData, NSError *error){
stepslabel.text = [pedometerData.numberOfSteps stringValue];
}];
}
The problem with the original code above is the cmped variable gets deallocated at the end of the if statement, so the query is destroyed before it finishes.
By changing it to a strong property, it is retained in memory for the life of the class.
It seems really odd but I got it working by not declaring in the .h or before using it. What worked was declaring as #property CMPedometer *cmped; right after interface
I'm implementing iCloud + Core Data for Mac OS and I'm having a major issue with mergeChangesFromContextDidSaveNotification.
When NSPersistentStoreDidImportUbiquitousContentChangesNotification is posted, I'm calling the following method:
- (void)mergeChangesFromNotification:(NSNotification *)note
{
self.managedObjectContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;
[self.managedObjectContext performBlock:^{
[self.managedObjectContext mergeChangesFromContextDidSaveNotification:note];
}];
// ....
}
The problem is that mergeChangesFromContextDidSaveNotification: does not return and, also, takes up more and more memory until the system runs out space.
Any thoughts on what the problem might be? I'm doing almost the same thing on iOS and works just fine.
Thanks!
I finally found the bug - and as I expected, it was quite stupid one:
I was merging the changes into the wrong context.
Using the iTunes Scripting Bridge interface, I need to fetch a particular iTunesTrack by its persistentID. I closely examined the header file produced sdp/sdef but it looks like there is no method in the existing interface for performing any kind of query for a track based on any parameter. The next idea I had was to enumerate all of the tracks examining each for a match.
The implication is that this would be slow; the larger the target library the worse the performance. I'm wondering if anyone has a proven solution to this problem that doesn't involve examining every track returned from the scripting bridge, one at a time?
At get a specific track in itunes via ScriptingBridge, Arr MiHardies states that he came up with a solution and would post it but apparently, he never got around to it.
The trick is to get the entire iTunes library as an array, then use Cocoa's NSPredicate filtering to find what you want.
iTunesApplication *iTunes = [SBApplication applicationWithBundleIdentifier:#"com.apple.iTunes"];
SBElementArray *iTunesSources = [iTunes sources];
iTunesSource *library;
for (iTunesSource *thisSource in iTunesSources) {
if ([thisSource kind] == iTunesESrcLibrary) {
library = thisSource;
break;
}
}
SBElementArray *libraryPlaylists = [library libraryPlaylists];
iTunesLibraryPlaylist *libraryPlaylist = [libraryPlaylists objectAtIndex:0];
SBElementArray *musicTracks = [self.libraryPlaylist fileTracks];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"persistentID == %#", persistentID];
[musicTracks filterUsingPredicate:predicate];
In general it's often a good rule of thumb to do as little as possible with Scripting Bridge methods—use them to get the data out, then use normal Cocoa methods for everything else.
I am making minor edits to a QTMovie in an application using NSDocument architecture (such as adding a track, as shown below). After the edit, I want to save to the original file. However, I keep getting a 'file is busy' error. I assume this is due to some oversight I made in the handling of the files, or a failure in how I am using NSDocument. Any tips would be helpful! Here is (some of) the relevant code:
// open file that has the track I want to add to my movie
QTMovie* tempMovie = [QTMovie movieWithURL:outputFileURL error:nil];
// Use old API to add the track
AddMovieSelection([movie quickTimeMovie], [tempMovie quickTimeMovie]);
// get the filename from the NSDocument
NSString *filename = [[self fileURL] path];
NSLog(#"writing to filename: %#", filename);
// FLATTEN the movie file so I don't get external references
NSMutableDictionary *attributes = [NSMutableDictionary dictionaryWithCapacity:1];
[attributes setObject:[NSNumber numberWithBool:YES] forKey:QTMovieFlatten];
// attempt to write
NSError *error;
// this is where I get the "file is busy"
if (![movie writeToFile:filename withAttributes:attributes error:&error]) {
NSLog(#"Error: %#", [error localizedDescription]);
NSRunAlertPanel(#"Error", [error localizedDescription], nil, nil, nil);
}
Do I have to first release the movie in my NSDocument? What is the "proper" way to do that? Keep in mind, I am not necessarily finished with this document, I am not closing it. I have just finished this operation, and I want the file on disk to reflect my changes. I would love to use [movie updateMovieFile], but that call doesn't seem to flatten the movie. I don't want any external references in my file.
I am not too familiar with the QuickTime C API, so I honestly can't tell you anything about what is going wrong there. Absolute guesswork: Maybe a call to EndMediaEdits is missing?
Though that shouldn't be required by AddMovieSelection, you said "[...] such as adding a track [...]". So maybe there is something else going on, like AddMediaSample or something similar?
That said, if you don't need to target anything below 10.5 and all you need to do is add some segment from another movie, you can achieve that without dropping down to the C API:
Have a look at
-[QTMovie insertSegmentOfTrack:fromRange:scaledToRange:]
and
-[QTMovie insertSegmentOfMovie:fromRange:scaledToRange:], if you want to have the inserted segment "overlayed" (temporally speaking).
-[QTMovie insertSegmentOfMovie:timeRange:atTime:] and -[QTMovie insertSegmentOfTrack:timeRange:atTime:], if you want { movieA.firstPart, movieB, movieA.secondPart }.
Do I have to first release the movie in my NSDocument?
You mean in order to write it to disk? No: That should even result in a crash.
The role of release is to handle memory-management. It doesn't have much to do with the busy-state of a file.
Turns out I just wasn't using the NSDocument architecture properly. When I changed it to use Save/SaveAs properly, this problem went away.
Background
I've already posted a question about the basics of sharing a Core Data store between processes.
I'm trying to implement the recommendations given and I'm running into problems.
My Goal
I have two processes - the Helper App and the UI. They both share a single data store. I want the UI to update it's NSManagedObjectContext when the Helper App has saved new data to the store.
Current Program Flow
The Helper App Process writes data to the Store.
In the Helper App, I listen for NSManagedObjectContextDidSaveNotification notifications.
When the context is saved, I encode the inserted, deleted and updated objects using their URI representations and NSArchiver.
I send an NSNotification to the NSDistributedNotificationCenter with this encoded dictionary as the userInfo.
The UI Process is listening for the save notification. When it receives the notification, it unarchives the userInfo using NSUnarchiver.
It looks up all the updated/inserted/deleted objects from the URIs given and replaces them with NSManagedObjects.
It constructs an NSNotification with the updated/inserted/deleted objects.
I call mergeChangesFromContextDidSaveNotification: on the Managed Object Context of the UI Process, passing in the NSNotification I constructed in the previous step.
The Problem
Inserted objects are faulted into the UI Managed Object Context fine and they appear in the UI. The problem comes with updated objects. They just don't update.
What I've tried
The most obvious thing to try would
be to pass the save Notification
from the Helper App process to the
UI process. Easy, right? Well, no.
Distributed Notifications won't
allow me to do that as the userInfo
dictionary is not in the right
format. That's why I'm doing all the
NSArchiving stuff.
I've tried calling
refreshObject:mergeChanges:YES on
the NSManagedObjects to be updated,
but this doesn't seem to have any
effect.
I've tried performing the
mergeChangesFromContextDidSaveNotification:
selector on the main thread and the
current thread. Neither seems to
affect the result.
I've tried using
mergeChangesFromContextDidSaveNotification:
before between threads, which of
course is much simpler and it worked
perfectly. But I need this same
functionality between processes.
Alternatives?
Am I missing something here? I'm consistently getting the feeling I'm making this much more complex than it needs to be, but after reading the documentation several times and spending a few solid days on this, I can't see any other way of refreshing the MOC of the UI.
Is there a more elegant way of doing this? Or am I just making a silly mistake somewhere in my code?
The Code
I've tried to make it as readable as possible, but it's still a mess. Sorry.
Helper App Code
-(void)workerThreadObjectContextDidSave:(NSNotification *)saveNotification {
NSMutableDictionary *savedObjectsEncodedURIs = [NSMutableDictionary dictionary];
NSArray *savedObjectKeys = [[saveNotification userInfo] allKeys];
for(NSString *thisSavedObjectKey in savedObjectKeys) {
// This is the set of updated/inserted/deleted NSManagedObjects.
NSSet *thisSavedObjectSet = [[saveNotification userInfo] objectForKey:thisSavedObjectKey];
NSMutableSet *thisSavedObjectSetEncoded = [NSMutableSet set];
for(id thisSavedObject in [thisSavedObjectSet allObjects]) {
// Construct a set of URIs that will be encoded as NSData
NSURL *thisSavedObjectURI = [[(NSManagedObject *)thisSavedObject objectID] URIRepresentation];
[thisSavedObjectSetEncoded addObject:thisSavedObjectURI];
}
// Archive the set of URIs.
[savedObjectsEncodedURIs setObject:[NSArchiver archivedDataWithRootObject:thisSavedObjectSetEncoded] forKey:thisSavedObjectKey];
}
if ([[savedObjectsEncodedURIs allValues] count] > 0) {
// Tell UI process there are new objects that need merging into it's MOC
[[NSDistributedNotificationCenter defaultCenter] postNotificationName:#"com.synapticmishap.lapsus.save" object:#"HelperApp" userInfo:(NSDictionary *)savedObjectsEncodedURIs];
}
}
UI Code
-(void)mergeSavesIntoMOC:(NSNotification *)notification {
NSDictionary *objectsToRefresh = [notification userInfo];
NSMutableDictionary *notificationUserInfo = [NSMutableDictionary dictionary];
NSArray *savedObjectKeys = [[notification userInfo] allKeys];
for(NSString *thisSavedObjectKey in savedObjectKeys) {
// Iterate through all the URIs in the decoded set. For each URI, get the NSManagedObject and add it to a set.
NSSet *thisSavedObjectSetDecoded = [NSUnarchiver unarchiveObjectWithData:[[notification userInfo] objectForKey:thisSavedObjectKey]];
NSMutableSet *savedManagedObjectSet = [NSMutableSet set];
for(NSURL *thisSavedObjectURI in thisSavedObjectSetDecoded) {
NSManagedObject *thisSavedManagedObject = [managedObjectContext objectWithID:[persistentStoreCoordinator managedObjectIDForURIRepresentation:thisSavedObjectURI]];
[savedManagedObjectSet addObject:thisSavedManagedObject];
// If the object is to be updated, refresh the object and merge in changes.
// This doesn't work!
if ([thisSavedObjectKey isEqualToString:NSUpdatedObjectsKey]) {
[managedObjectContext refreshObject:thisSavedManagedObject mergeChanges:YES];
[managedObjectContext save:nil];
}
}
[notificationUserInfo setObject:savedManagedObjectSet forKey:thisSavedObjectKey];
}
// Build a notification suitable for merging changes into MOC.
NSNotification *saveNotification = [NSNotification notificationWithName:#"" object:nil userInfo:(NSDictionary *)notificationUserInfo];
[managedObjectContext performSelectorOnMainThread:#selector(mergeChangesFromContextDidSaveNotification:)
withObject:saveNotification
waitUntilDone:YES];
}
I used the method in
http://www.mlsite.net/blog/?p=518
then every object is correctly faulted but the faults are fetch in cache so still no update
I had to do
[moc stalenessInterval = 0];
And it finally worked, with relationship.
You're looking for - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag I believe.
This will refresh the object with the info in the persistent store, merging changes if you want.
I'd go with Mike's suggestion and just watch the store file for changes.
Though it may not be the most efficient, I've had success using - [NSManagedObjectContext reset] from a second process when there's a change to a store. In my case case, the code is fairly linear — all I do is run a fetch request for some data after resetting. I don't know how this will work with bindings and a complicated UI, but you may be able to post a notification to manually update things if it's not handled automatically.
I had this exact same issue with an iPhone app that I've been working on. In my case, the solution involved setting the Context's stalenessInterval to something suitably infinitesimal (e.g., 0.5 seconds).
This works, except for sandboxes apps. You can't send a notification with a user info dict. Instead consider some other IPC like XPC or DO.
On a side note, using NSDustributedNotificationCenter is not always 100% if the system is busy.
Setting stalenessInterval of managed object context works. My case involves multiple threads instead of process though.
Starting with iOS 9, you should now use mergeChangesFromRemoteContextSave:intoContexts:. See this for an explanation: https://www.innoq.com/en/blog/ios-writing-core-data-in-today-extension/