Creating movie on background thread
Creating movie on background thread
- Subject: Creating movie on background thread
- From: "Roger Herikstad" <email@hidden>
- Date: Tue, 2 Sep 2008 12:50:19 +0800
Hi lists,
Sorry for the cross-posting, but I thought my issue to relevant for
both lists. I need to create an image sequence of some plots from a
graphing application that i'm writing, and I would like to be able to
do this on a background thread. Basically, I ask my app to plot some
signals on screen (~1000 individual signals) and once I'm happy with
how the signals look, I'd like to create an image sequence so that if
I want to look at those signals again, I have only to load up the
movie instead of plotting them again. I'm using an NSOperation object
for constructing my movie. The relevant code is
- (void)createMovieInRect:(NSRect)aRect
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSError *error = [NSError errorWithDomain: @"thisDomain" code: 1
userInfo: nil];
QTMovie *movie = [[QTMovie alloc] initToWritableFile: output_file
error: &error];
//QTMovie *movie = [QTMovie movie];
//NSImage *image = NULL;
QTTime duration = QTMakeTime(1,10);
NSDictionary *attribs = nil;
attribs = [NSDictionary dictionaryWithObjectsAndKeys:@"avc1",
QTAddImageCodecType,
[NSNumber numberWithLong:codecHighQuality],
QTAddImageCodecQuality,
nil];
QTTime dur;
BOOL success = NO;
int i;
NSLog([NSString stringWithFormat: @"Creating movie of %d
frames\n",num_waves ]);
for(i=0;i< num_waves;i++)
{
[_image release];
_image = NULL;
[self setdrawWaves: [NSIndexSet indexSetWithIndex: i]];
[self drawInRect: aRect];
[movie addImage: [self image] forDuration: duration
withAttributes: attribs];
success = [movie updateMovieFile];
CGContextRestoreGState(context);
}
[movie release];
[_image release];
[pool release];
}
When I create my operation object and add it to the queue, the process
of creating the movie seems exceedingly slow, 1 hour+ to create a
movie consisting of 1,000 images. My question is, is there something
in the QTKit that prevents it from working properly on a background
thread? There are probably other issues with my code that could be
optimised, but I just wanted to rule out multi-threading problems.
Thanks!
~ Roger
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