iOS AVPlayer播放没有.mp3后缀的链接

把原来的：

AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:urlStr]];
AVPlayer *player = [[AVPlayer alloc] initWithPlayerItem:playerItem];

指定MP3类型，改为：

NSString *mimeType = @"audio/mp3";
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL URLWithString:urlStr] options:@{@"AVURLAssetOutOfBandMIMETypeKey": mimeType}];
AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithAsset:asset];
AVPlayer *player = [[AVPlayer alloc] initWithPlayerItem:playerItem];