Question

我有一组视频剪辑，我想将它们合并在一起，然后在上面添加水印。

我可以单独执行这两项功能，但是在一起执行这些功能时会出现问题。

所有要合并的剪辑都是1920x1080或960x540。

出于某种原因，AVAssetExportSession无法很好地显示它们。

以下是基于3种不同场景的2个错误： Merged Screenshot

此图片的结果是：

合并剪辑

正如您所看到的，这里没有任何错误，输出视频会产生所需的效果。

然而，当我尝试添加水印时，会产生以下问题： Merged and watermarked

此图片的结果是：

合并剪辑
在上面加上水印

BUG 1：视频中的某些片段会因任何原因调整大小，而其他片段则不会。

Merged, watermarked, and edited

此图片的结果是：

合并剪辑
调整960x540到1920x1080
在上面加上水印

错误2 现在需要调整大小的剪辑会调整大小，但旧的未显示剪辑仍然存在。

合并/调整代码：

-(void) mergeClips{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];      

    AVMutableCompositionTrack *mutableVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

    AVMutableCompositionTrack *mutableAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

    // loop through the list of videos and add them to the track
    CMTime currentTime = kCMTimeZero;

    NSMutableArray* instructionArray = [[NSMutableArray alloc] init];
    if (_clipsArray){
        for (int i = 0; i < (int)[_clipsArray count]; i++){
            NSURL* url = [_clipsArray objectAtIndex:i];

            AVAsset *asset = [AVAsset assetWithURL:url];

            AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
            AVAssetTrack *audioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

            CGSize size = videoTrack.naturalSize;
            CGFloat widthScale = 1920.0f/size.width;
            CGFloat heightScale = 1080.0f/size.height;

// lines that performs resizing
            AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:mutableVideoTrack];
            CGAffineTransform scale = CGAffineTransformMakeScale(widthScale,heightScale);
            CGAffineTransform move = CGAffineTransformMakeTranslation(0,0);
            [layerInstruction setTransform:CGAffineTransformConcat(scale, move) atTime:currentTime];
            [instructionArray addObject:layerInstruction];


            [mutableVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                                ofTrack:videoTrack
                                 atTime:currentTime error:nil];

            [mutableAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                                ofTrack:audioTrack
                                 atTime:currentTime error:nil];

            currentTime = CMTimeMakeWithSeconds(CMTimeGetSeconds(asset.duration) + CMTimeGetSeconds(currentTime), asset.duration.timescale);
        }
    }

    AVMutableVideoCompositionInstruction * mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, currentTime);
    mainInstruction.layerInstructions = instructionArray;


    // 4 - Get path
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *lastPostedDayPath = [documentsDirectory stringByAppendingPathComponent:@"lastPostedDay"];

    //Check if folder exists, if not create folder
    if (![[NSFileManager defaultManager] fileExistsAtPath:lastPostedDayPath]){
        [[NSFileManager defaultManager] createDirectoryAtPath:lastPostedDayPath withIntermediateDirectories:NO attributes:nil error:nil];
    }


    NSString *fileName = [NSString stringWithFormat:@"%li_%li_%li.mov", (long)_month, (long)_day, (long)_year];

    NSString *finalDayPath = [lastPostedDayPath stringByAppendingPathComponent:fileName];

    NSURL *url = [NSURL fileURLWithPath:finalDayPath];

    BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:finalDayPath];
    if (fileExists){
        NSLog(@"file exists");
        [[NSFileManager defaultManager] removeItemAtURL:url error:nil];
    }

    AVMutableVideoComposition *mainComposition = [AVMutableVideoComposition videoComposition];

    mainComposition.instructions = [NSArray arrayWithObject:mainInstruction];
    mainComposition.frameDuration = CMTimeMake(1, 30);
    mainComposition.renderSize = CGSizeMake(1920.0f, 1080.0f);

    // 5 - Create exporter
    _exportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                            presetName:AVAssetExportPresetHighestQuality];
    _exportSession.outputURL=url;
    _exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    _exportSession.shouldOptimizeForNetworkUse = YES;
    _exportSession.videoComposition = mainComposition;

    [_exportSession exportAsynchronouslyWithCompletionHandler:^{
        [merge_timer invalidate];
        merge_timer = nil;

        switch (_exportSession.status) {
            case AVAssetExportSessionStatusFailed:
                NSLog(@"Export failed -> Reason: %@, User Info: %@",
                      _exportSession.error.localizedDescription,
                      _exportSession.error.userInfo.description);
                [self showSavingFailedDialog];
                break;

            case AVAssetExportSessionStatusCancelled:
                NSLog(@"Export cancelled");
                [self showSavingFailedDialog];

                break;

            case AVAssetExportSessionStatusCompleted:
                NSLog(@"Export finished");
                [self addWatermarkToExportSession:_exportSession];

                break;

            default:
                break;
        }
    }];
});
}

完成此操作后，我会通过另一个只添加水印的导出会话来运行它。

我的代码或流程中是否存在错误？有没有更简单的方法来实现这一目标？

感谢您的时间！

Answer 1

我能够解决我的问题。出于某种原因，AVAssetExportSession实际上不会创建合并剪辑的“平面”视频文件，因此在添加导致它们调整大小的水印时，它仍会识别较低分辨率的剪辑及其位置。

我要解决的问题是，首先使用AVAssetWriter合并我的剪辑并创建一个“平面”文件。然后，我可以在没有调整大小问题的情况下添加水印。

希望这有助于将来可能遇到此问题的任何人！

Answer 2

我也遇到了同样的问题，您可以在一个视频结束后设置不透明度，如下所示：

[layerInstruction setOpacity:0.0 atTime:duration];

合并具有不同分辨率的剪辑

2 个答案: