如何判断QTMovie何时开始播放？

[qtMovie addObserver:self forKeyPath:@"rate" options:NSKeyValueObservingOptionNew context:nil];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"rate"]) {
        if (self.qtMovie.rate > 0) {
            NSLog(@"QTMovie开始播放");
        } else {
            NSLog(@"QTMovie暂停播放");
        }
    }
}

[qtMovie addObserver:self forKeyPath:@"currentTime" options:NSKeyValueObservingOptionNew context:nil];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"currentTime"]) {
        if (self.qtMovie.currentTime > 0) {
            NSLog(@"QTMovie开始播放");
        } else {
            NSLog(@"QTMovie准备播放");
        }
    }
}