Question

我正在使用Brad Larson的优秀图书馆GPUImage进行申请。目前我遇到了一个问题。我的应用程序捕获10秒视频，之后允许filter申请。在filters中应用GPUImageMovie时，我无法暂停播放并应用新的filter，以便视频可以在不从头开始的情况下连续播放。

我看到了一个开放的github问题here。如果有人遇到类似问题并找到解决方案，请发布您的答案。提前谢谢。

Answer 1

最后我在经过太多搜索后尝试修复此问题。我们需要使用AVPlayerItem而不是URL来启动GPUImageMovie。我从here得到了这个有价值的线索。

我发布了我目前在我的应用程序中使用的代码，它正在按预期工作。但iPod 6.1中存在性能问题，我正在努力改进它。

设置GPUImageMovie的初始方法，

- (void)setupVideo
{
    playerItem = [[AVPlayerItem alloc]initWithURL:self.recordSession.outputUrl];
    player = [AVPlayer playerWithPlayerItem:playerItem];

    movieFile = [[GPUImageMovie alloc] initWithPlayerItem:playerItem];

    movieFile.runBenchmark = YES;
    movieFile.playAtActualSpeed = YES;
    [self.view sendSubviewToBack:self.videoView];

    [movieFile addTarget:filter];
    [filter addTarget:self.videoView];

    [movieFile startProcessing];
    movieRunning = YES;

    dispatch_async(dispatch_get_main_queue(), ^{
        self.playButton.hidden = YES;
    });

    player.rate = 1.0;
}

当用户点击过滤器按钮时，会调用此方法。

- (void)filterClicked:(UIButton *)button
{
    // Set paused time. If player reaches end of the video, set pausedTime to 0.
    if (CMTIME_COMPARE_INLINE(pausedTime, !=,  player.currentItem.asset.duration)) {
        pausedTime = player.currentTime;
    } else {
        pausedTime = CMTimeMake(0, 600.0);
    }
    [self.videoView setBackgroundColor:[UIColor clearColor]];

    [movieFile cancelProcessing];

    switch (button.tag)
    {
    case 0:
        filter = [[GPUImageFilter alloc] init];
        break;
    case 1:
        filter = [[GPUImageColorInvertFilter alloc] init];
        break;
    case 2:
        filter = [[GPUImageEmbossFilter alloc] init];
        break;
    case 3:
        filter = [[GPUImageGrayscaleFilter alloc] init];
        break;
    default:
        filter = [[GPUImageFilter alloc] init];
        break;
    }

    [self filterVideo];

}

生成过滤器后，此方法将处理视频播放恢复。

- (void)filterVideo {

    // AVPlayerItem is initialized with required url

    playerItem = [[AVPlayerItem alloc]initWithURL:self.outputUrl]; 
    [player replaceCurrentItemWithPlayerItem:playerItem];

    //GPUImageMovie is initialized with AVPlayerItem

    movieFile = [[GPUImageMovie alloc] initWithPlayerItem:playerItem];

    movieFile.runBenchmark = YES;
    movieFile.playAtActualSpeed = YES;

    // Adding targets for movieFile and filter

    [movieFile addTarget:filter];
    [filter addTarget:self.videoView]; // self.videoView is my GPUImageView

    [movieFile startProcessing];
    movieRunning = YES;

    dispatch_async(dispatch_get_main_queue(), ^{
        self.playButton.hidden = YES;
    });

    // Player rate is set to 0 means player is paused

    [player setRate:0.0];

    // Seeking to the point where video was paused

     if (CMTIME_COMPARE_INLINE(pausedTime, !=, player.currentItem.asset.duration)) {
        [player seekToTime:pausedTime];
    }
    [player play];
}

Answer 2

对于我来说，使用AVPlayerItem是不可行的（我使用合成）。

相反，我编写了以下代码：

class PausableGPUImageMovie: GPUImageMovie {
    var isPaused = false

    override func readNextVideoFrame(from readerVideoTrackOutput: AVAssetReaderOutput!) -> Bool {
        while isPaused {
            usleep(100_000)
        }
        return super.readNextVideoFrame(from: readerVideoTrackOutput)
    }
}

非常垃圾，但是随时可以改善它。

应用过滤器时GPUImageMovie暂停

2 个答案: