我正在尝试使用 AVURLAsset 加载 webvtt 文件。
下面是我的代码。
NSString *urlAddress = @"http://somewhere/some.vtt";
NSURL *urlStream = [[NSURL alloc] initWithString:urlAddress];
AVAsset *avAsset = [AVURLAsset URLAssetWithURL:urlStream options:nil];
NSArray *requestKeys = [NSArray arrayWithObjects:@"tracks",@"playable",nil];
[avAsset loadValuesAsynchronouslyForKeys:requestKeys completionHandler:^{
dispatch_async(dispatch_get_main_queue(),^{
//complete block here
AVKeyValueStatus status =[avAsset statusOfValueForKey:@"tracks" error:nil];
if(status == AVKeyValueStatusLoaded) {
//loaded block !
//Question 1
CMTime assetTime = [avAsset duration];
Float64 duration = CMTimeGetSeconds(assetTime);
NSLog(@"%f", duration);
//Question 2
AVMediaSelectionGroup *subtitle = [avAsset mediaSelectionGroupForMediaCharacteristic: AVMediaCharacteristicLegible];
NSLog(@"%@", subtitle);
}
else {
//don’t load block !
}
});
}];
问题1:总是进入“Loaded Block”,但是我发现avAsset的duration不完整,是不是数据没有加载?我应该如何修改它?
问题 2:我试图将它用于我的 avplayer 的字幕,但 AVMediaSelectionGroup 始终为空。我应该怎么办?