将 AVPlayerViewController.player 设置为 nil 会中断隐藏式字幕

Question

根据 Apple 的文档，如果您想在后台播放视频的音频内容，则必须在移动应用程序时断开 AVPlayer 与其 AVPlayerViewController 或 AVPlayerLayer 的连接到后台以防止音频自动暂停：

https://developer.apple.com/documentation/avfoundation/media_assets_playback_and_editing/creating_a_basic_video_player_ios_and_tvos/playing_audio_from_a_video_asset_in_the_background

我注意到在 iOS 13 中，这样做会导致隐藏式字幕中断。我创建了一个新项目（单视图应用程序）来为这个问题创建一个最小的重现案例。我的情节提要由一个视图和一个按钮组成，按钮作为一个动作连接到我的视图控制器 ("playPressed")。这是我的 ViewController.m:

的代码

//
//  ViewController.m
//  AVPlayerViewControllerBug
//
//  Created by Steven Barnett on 9/27/19.
//  Copyright © 2019 BlueFrame Tech. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
{
    @private
    AVPlayerViewController *controller;
    AVPlayer *player;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    controller = [[AVPlayerViewController alloc] init];
    player = [[AVPlayer alloc] initWithURL:[NSURL URLWithString:@"https://vcloud.blueframetech.com/file/hls/143758.m3u8"]];
    controller.player = player;

    [player addObserver:self forKeyPath:@"rate" options:0 context:nil];

}

- (IBAction)playPressed:(id)sender {
    [self presentViewController:controller animated:YES completion:nil];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    // Since we're ONLY observing "rate" on the player, assume
    // that's what changed to call this
    AVPlayer *player = (AVPlayer*)object;

    if (player.rate == 0)
    {
        // Unbind the player from the view controller when paused
        controller.player = nil;

        // Since I haven't built custom controls for the player,
        // when it's unbound there's no way to hit the play
        // button. So we'll just start playing after a timer
        // has elapsed
        [NSTimer scheduledTimerWithTimeInterval:2.0 repeats:NO block:^(NSTimer * _Nonnull timer) {
            [player play];
        }];
    }
    else
    {
        // Re-bind the player when playing
        controller.player = player;
    }
}

@end

如果您将这段代码复制到您自己的应用程序中，或者自己尝试一下，您会发现调用 controller.player = nil 时，它会导致字幕在 AVPlayer 上停止工作。我发现修复它的唯一方法是删除 AVPlayer 对象并创建一个全新的 AVPlayer 来替换它。

是否有我遗漏的东西、我不知道的方法调用或我误解的东西？或者这只是一个 iOS 13 错误？

Answer 1

我找到了一个不太优雅的解决方案来解决这个问题！

当您调用controller.player = nil;时，您还必须完全销毁AVPlayerViewController：[controller.view removeFromSuperview]; controller = nil;

然后当你想再次设置播放器时，你创建一个新的AVPlayerViewController。这会导致音频和视频中出现一个小插曲（大约 0.1 秒），但字幕会起作用！

将 AVPlayerViewController.player 设置为 nil 会中断隐藏式字幕

Setting AVPlayerViewController.player to nil breaks closed captions

ios

objective-c

avplayer