AVPlayer物品获得持续时间 [英] AVPlayer Item get a nan duration

问题描述

我正在播放文件.网址中的mp3(按流). 我使用的是AVPlayer，当我试图获取构建进度条的总时间时，只要时间是零，我都会得到.

I'm playing a file. mp3 from url by stream. I'm using AVPlayer and when I am trying to get the total time to build a progress bar, I get whenever time is nan.

 NSError *setCategoryError = nil;
    if ([ [AVAudioSession sharedInstance] isOtherAudioPlaying]) { // mix sound effects with music already playing
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategorySoloAmbient error:&setCategoryError];
    } else {
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:&setCategoryError];
    }
    if (setCategoryError) {
        NSLog(@"Error setting category! %ld", (long)[setCategoryError code]);
    }
    NSURL *url = [NSURL URLWithString:@"http://..//46698"];

    AVPlayer *player = [AVPlayer playerWithURL:url];
    songPlayer=player;
    [songPlayer addObserver:self forKeyPath:@"status" options:0 context:nil];



- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if (object == songPlayer && [keyPath isEqualToString:@"status"]) {
        if (songPlayer.status == AVPlayerStatusFailed) {
            NSLog(@"AVPlayer Failed");

        } else if (songPlayer.status == AVPlayerStatusReadyToPlay) {
            NSLog(@"AVPlayerStatusReadyToPlay");
            [songPlayer play];
            [songPlayer addPeriodicTimeObserverForInterval:CMTimeMake(1, 1) queue:dispatch_get_main_queue() usingBlock:^(CMTime time){
                CMTime aux = [songPlayer currentTime];
                AVPlayerItem *item=[songPlayer currentItem];
                CMTime dur=[item duration];
                NSLog(@"%f/%f", CMTimeGetSeconds(aux),  CMTimeGetSeconds(dur));
            }];
        } else if (songPlayer.status == AVPlayerItemStatusUnknown) {
            NSLog(@"AVPlayer Unknown");

        }
    }
}

我已经尝试了一切.

[item duration]; /// Fail

[[item asset] duration]; /// Fail

没有任何作用

有人知道为什么吗?

推荐答案

在加载基础资产的持续时间之前，duration属性的值将报告为kCMTimeIndefinite.有两种方法可以确保只有在持续时间值可用后才能对其进行访问:

The value of duration property will be reported as kCMTimeIndefinite until the duration of the underlying asset has been loaded. There are two ways to ensure that the value of duration is accessed only after it becomes available:

1. 等待，直到AVPlayerItem的状态为AVPlayerItemStatusReadyToPlay.

注册以观察duration属性的键值，并请求初始值.如果初始值报告为kCMTimeIndefinite，则AVPlayerItem会在知道其值后立即通过键值观察方式通知您该项目持续时间的可用性.

Register for key-value observation of the duration property, requesting the initial value. If the initial value is reported as kCMTimeIndefinite, the AVPlayerItem will notify you of the availability of the item's duration via key-value observing as soon as its value becomes known.

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