如何在 iOS 中为正在运行的视频添加动态视觉效果？

Posted 2023-03-08

【中文标题】如何在 iOS 中为正在运行的视频添加动态视觉效果？

【英文标题】：How to add Dynamic Visual effects to running videos in iOS?

【发布时间】：2014-04-08 07:50:26

【问题描述】：

我想将视觉效果动态更改为正在运行的视频。我正在使用 GPUImage 框架来改变视觉效果。我从Here 下载了示例项目。在这个 GPUImage 中，我选择了 SimpleVideoFileFilter 示例。此示例使用一个过滤器运行，只是我修改了代码，目前它支持 10 个过滤器。我的问题是，视频文件正在 GPUImageView 中播放，现在我选择了另一个过滤器。突然间，视频效果也发生了变化。但是那个视频是从头开始的。我想为当前播放的视频动态更改过滤器。 我的代码是：

#pragma mark - Play Video with Effects

- (void)getVideo:(NSURL *)url

    movieFile = [[GPUImageMovie alloc] initWithURL:url];

    movieFile.runBenchmark = YES;
    movieFile.playAtActualSpeed = YES;
    //    filter = [[GPUImagePixellateFilter alloc] init];


    [movieFile addTarget:filter];

    // Only rotate the video for display, leave orientation the same for recording
    filterView = (GPUImageView *)self.view;
    [filter addTarget:filterView];

    // In addition to displaying to the screen, write out a processed version of the movie to disk
    NSString *pathToMovie = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Movie.m4v"];
    unlink([pathToMovie UTF8String]); // If a file already exists, AVAssetWriter won't let you record new frames, so delete the old movie
    NSURL *movieURL1 = [NSURL fileURLWithPath:pathToMovie];

    movieWriter = [[GPUImageMovieWriter alloc] initWithMovieURL:movieURL1 size:CGSizeMake(640.0, 480.0)];
    [filter addTarget:movieWriter];

    // Configure this for video from the movie file, where we want to preserve all video frames and audio samples
    movieWriter.shouldPassthroughAudio = YES;
    movieFile.audioEncodingTarget = movieWriter;
    [movieFile enableSynchronizedEncodingUsingMovieWriter:movieWriter];

    [movieWriter startRecording];
    [movieFile startProcessing];

    [movieWriter setCompletionBlock:^
        [filter removeTarget:movieWriter];
        [movieWriter finishRecording];
        UISaveVideoAtPathToSavedPhotosAlbum(pathToMovie, nil, nil, nil);
    ];


- (void)event:(UIButton*)sender

    [filter removeTarget:filterView];
    UIButton *selectedBtn = sender;
    [movieFile removeTarget:filter];
    switch (selectedBtn.tag)
    
        case 0:
            filter = [[GPUImageBrightnessFilter alloc] init];
            break;
        case 1:
            filter = [[GPUImageGrayscaleFilter alloc] init];
            break;
        case 2:
            filter = [[GPUImageSketchFilter alloc] init];
            break;
        case 3:
            filter = [[GPUImageToonFilter alloc] init];
            break;
        case 4:
            filter = [[GPUImageMonochromeFilter alloc] init];
            break;
        case 5:
            filter = [[GPUImagePixellateFilter alloc] init];
            break;
        case 6:
            filter = [[GPUImageCrosshatchFilter alloc] init];
            break;
        case 7:
            filter = [[GPUImageVignetteFilter alloc] init];
            break;
        case 8:
            filter = [[GPUImageColorInvertFilter alloc] init];
            break;
        case 9:
            filter = [[GPUImageLevelsFilter alloc] init];
            [(GPUImageLevelsFilter *)filter setRedMin:1.0 gamma:1.0 max:0.0 minOut:0.5 maxOut:0.5];
            break;

        default:
            break;        
    
    [self getVideo:movieURL];

请帮我解决这个问题。

【问题讨论】：

为什么每次更改过滤器设置时都重新运行[self getVideo:movieURL];？当然，这会重新启动您的视频。只需更改过滤器属性或更换过滤器，无需重新生成您的电影实例。您可以轻松地暂停电影、更改滤镜并重新启动电影以动态更改这些效果。

嗨 @BradLarson，首先感谢您提供宝贵的 GPUImage 框架。实际上对这个问题感到震惊。请帮我解决这个问题。我不知道如何动态更换过滤器。请您编辑上述代码并作为答案发布。

@BradLarson 如何暂停正在播放的电影？

我也面临同样的问题。请发布解决方案。

@QUserS - 发布解决方案。

【参考方案1】：

我自己找到了答案。解决办法是，

- (void)event:(UIButton*)sender

    //  isMoviePlayCompleted = NO;
    if (btnTag != sender.tag)
    
        btnTag = (int)sender.tag;
        NSLog(@"tag:%d",btnTag);
        [self applyFilter:sender.tag];
    

应用过滤器

    -(void) applyFilter:(NSInteger) tag
    
        [[NSFileManager defaultManager] removeItemAtURL:saveTempUrl error:nil];
        recording = NO;
        switch (tag)
        
            case 0:
                filter =nil;
                filter  = [[GPUImagePixellateFilter alloc] init];
                [(GPUImagePixellateFilter *)filter setFractionalWidthOfAPixel:0.0];
                break;
            case 1:
                filter =nil;
                filter = [[GPUImageGrayscaleFilter alloc] init];
                break;
            case 2:
                filter =nil;
                filter = [[GPUImageSketchFilter alloc] init];
                break;
            case 3:
                filter =nil;
                filter = [[GPUImageToonFilter alloc] init];
                break;
            case 4:
                filter =nil;
                filter = [[GPUImageMonochromeFilter alloc] init];
                break;
            case 5:
                filter =nil;
                filter = [[GPUImageVignetteFilter alloc] init];
                break;
      default:
                break;
        

        [self getVideo:movieURL];

使用效果播放视频

- (void)getVideo:(NSURL *)url


        [filter removeAllTargets];
        movieFile.audioEncodingTarget = nil;
        [movieWriter cancelRecording];
        [movieFile cancelProcessing];
        [movieWriter finishRecording];
        movieWriter = nil;
        movieFile = nil;
        filterView = nil;
    recording = YES;
    anAsset = [[AVURLAsset alloc] initWithURL:url options:nil];
    movieFile = [[GPUImageMovie alloc] initWithURL:url];
        movieFile.delegate = self;
        movieFile.runBenchmark = NO;
    movieFile.playAtActualSpeed = YES;

        [movieFile addTarget:filter];

    // Only rotate the video for display, leave orientation the same for recording
    filterView = (GPUImageView *)self.view;

        [filter addTarget:filterView];

        NSString *pathName = [NSString stringWithFormat:@"Doc.MOV"];
        // In addition to displaying to the screen, write out a processed version of the movie to disk
        NSString *pathToMovie = [NSTemporaryDirectory() stringByAppendingPathComponent:pathName];
        NSFileManager *fileTmp = [[NSFileManager alloc] init];
        if ([fileTmp fileExistsAtPath:pathToMovie]) 
            [fileTmp removeItemAtPath:pathToMovie error:nil];
        
        unlink([pathToMovie UTF8String]); // If a file already exists, AVAssetWriter won't let you record new frames, so delete the old movie
        saveTempUrl =  [NSURL fileURLWithPath:pathToMovie];
        movieWriter = [[GPUImageMovieWriter alloc] initWithMovieURL:saveTempUrl size:size];
        [filter addTarget:movieWriter];
[movieFile enableSynchronizedEncodingUsingMovieWriter:movieWriter];
    [movieWriter startRecording];
    [movieFile startProcessing];
    __unsafe_unretained typeof(self) weakSelf = self;
    [weakSelf->movieWriter setCompletionBlock:^

        NSLog(@"write completed");
        [filter removeTarget:movieWriter];
        [movieWriter finishRecording];
        movieWriter = nil;
        movieFile = nil;
        filterView = nil;
        recording = NO;
        if (saveFilter)
        
            saveFilter = NO;
            UISaveVideoAtPathToSavedPhotosAlbum([saveTempUrl path], self, @selector(video:didFinishSavingWithError:contextInfo:), nil);
            shareFilter = YES;
        

    ];

就是这样。现在，当我选择任何过滤器时，它都会重新填充。所以内存问题解决了。现在它适用于我的应用程序。

【讨论】：

抱歉回复晚了，感谢您的解决方案。我刚刚试用了您的代码，但没有得到预期的结果。每当更改过滤器时，我都需要恢复视频。目前它正在从应用每个过滤器的起点开始播放。请提出建议。

【参考方案2】：

// Use this code

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieFinished) name:MPMoviePlayerPlaybackDidFinishNotification object:videoPlayer];
[videoPlayer play];


-(void)movieFinished

[videoPlayer play];
  



-(void) playTheVideo:(NSURL *)videoURL

NSTimeInterval time= videoPlayer.currentPlaybackTime;
UIView *parentView = imageViewFiltered; // adjust as needed
CGRect bounds = parentView.bounds; // get bounds of parent view
CGRect subviewFrame = CGRectInset(bounds, 0, 0); 
videoPlayer.view.frame = subviewFrame;
videoPlayer.view.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
[parentView addSubview:videoPlayer.view];
videoPlayer.contentURL = videoURL;
[videoPlayer setCurrentPlaybackTime:time];
[videoPlayer stop];
NSLog(@"Videoplayer stop or play in this view ");
[videoPlayer play];
self.showLoading = NO;
self.showLoading =NO;