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[算法]iOS 视频添加水印,合成视频两种方案(整体渲染和分割渲染)

[算法]iOS 视频添加水印,合成视频两种方案(整体渲染和分割渲染)

现手机里有一段视频,通过APP给他添加一个水印。iOS提供了在视频上添加layer的接口,添加一个水印还是很方便的(添加水印)。添加完水印有一个渲染过程,在手机这种设备上还是比较慢的,比如:对1分钟的高清视频(960x540)进行渲染需要20秒左右。如何在现有API基础上提高渲染速度,提升用户体验,成了问题。笔者发现两种渲染方法:

        先看图,这有一个6秒的视频,我抓了四张关键帧。只在第2,3两张关键帧上添加字幕(一个关键帧代表1.5秒。所以,两个关键帧就代表是3秒时长)




        第一种方案:视频分割 + 逐段渲染 + 合并

            将视频分割为3端,即第1、第2,3、第4。有水印的是一组,没水印也是一组。对第2,3渲染。最后将三段视频合并到一起。

        第二种方案:整体渲染

            水印虽然不是从一开始出现,但是,我们可以对layer添加动画(参考下面OC代码)。

举个例子,假如水印少的情况。比如只对第一帧添加水印。分割渲染方案是3.0秒,整体渲染方案是3.5秒。假如水印多的情况,第1,2,3帧都有水印。分割渲染方案是4.1秒,整体渲染方案还是3.5秒。通过结果得出一点结论:整体渲染,无论水印多还是少,耗时是一样的。分割渲染怎么会有这么个差别呢?

        分割渲染:由于涉及三步:1.分割,2.渲染视频,3.合并视频。每一步都需要时间。根据测试经验,第一步分割视频的时间很少,可以忽略。那么就剩下渲染和合并时间了。就拿刚才6秒的视频来说:一张水印和三张水印。合并视频时间是一样的。都是两段(一段1.5秒,另外一段4.5秒)。但是水印多了渲染时间就长了。

        最后得出结论:水印少的时候,使用分割渲染方法。水印多的情况使用整体渲染。


整体渲染代码:


#define kEffectVideoFileName_Animation @"tmpMov-effect.mov"

    - (void)renderWholeVideo:(AVAsset *)asset{

    // 1 - Early exit if there's no video file selected

    if (!asset) {

        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Please Load a Video Asset First"

                                                       delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

        [alert show];

        return;

    }

    

    // 2 - Create AVMutableComposition object. This object will hold your AVMutableCompositionTrack instances.

    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];

    

    // 3 - Video track

    AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo

                                                                        preferredTrackID:kCMPersistentTrackID_Invalid];

    [videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)

                        ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]

                         atTime:kCMTimeZero error:nil];

    

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

    [audioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[asset tracksWithMediaType:AVMediaTypeAudio][0] atTime:kCMTimeZero error:nil];

    

    // 3.1 - Create AVMutableVideoCompositionInstruction

    AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);

    

    // 3.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.

    __block     CGSize naturalSize;

    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [self transformVideo:asset track:videoTrack isVideoAssetPortrait:^(CGSize finalSize) {

        naturalSize = finalSize;

    }];

    [videolayerInstruction setOpacity:0.0 atTime:asset.duration];

    

    // 3.3 - Add instructions

    mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

    

    AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

    

    

    float renderWidth, renderHeight;

    renderWidth = naturalSize.width;

    renderHeight = naturalSize.height;

    mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);

    mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];

    mainCompositionInst.frameDuration = CMTimeMake(1, 30);

    

    

    

    [self applyVideoEffectsWithAnimation:mainCompositionInst size:naturalSize];

    

    

    NSString *myPathDocs = [NSTemporaryDirectory() stringByAppendingPathComponent:kEffectVideoFileName_Animation];

    NSURL *url = [NSURL fileURLWithPath:myPathDocs];

    /*先移除旧文件*/

    [PublicUIMethod removeFile:url];

    

    // 5 - Create exporter

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition

                                                                      presetName:AVAssetExportPresetHighestQuality];

    [self.exportSessions addObject:exporter];

    exporter.outputURL=url;

    exporter.outputFileType = AVFileTypeQuickTimeMovie;

    exporter.shouldOptimizeForNetworkUse = YES;

    exporter.videoComposition = mainCompositionInst;

    weakifyself;

    [exporter exportAsynchronouslyWithCompletionHandler:^{

        strongifyself;

        dispatch_async(dispatch_get_main_queue(), ^{

            switch ([exporter status]) {

                case AVAssetExportSessionStatusFailed:

                    

                    DDLogWarn(@"render Export failed: %@ and order : %d", [exporter error], 0);

                    break;

                case AVAssetExportSessionStatusCancelled:

                    

                    NSLog(@"render Export canceled order : %d", 0);

                    break;

                default:

                {

                    NSLog(@"'%@' render finish",[myPathDocs lastPathComponent]);

                    [self pushToPreviePage:myPathDocs];

                }

                    break;

            }

        });

    }];

    [self monitorSingleExporter:exporter];

}

 

- (void)applyVideoEffectsWithAnimation:(AVMutableVideoComposition *)composition size:(CGSize)size

{

    // Set up layer

    CALayer *parentLayer = [CALayer layer];

    CALayer *videoLayer = [CALayer layer];

    parentLayer.frame = CGRectMake(0, 0, size.width, size.height);

    videoLayer.frame = CGRectMake(0, 0, size.width, size.height);

    [parentLayer addSublayer:videoLayer];

    

    

    /**/

    CMTime timeFrame = [self frameTime];

    CGFloat granularity = CMTimeGetSeconds(timeFrame);

    /*caption layer*/

    for (int j=0; j<self.effectsArray.count; j++) {

        NSArray* effectSeries = (NSArray *)self.effectsArray[j];

        FSVideoCaptionDescriptionModel *description = [[effectSeries firstObject] as:FSVideoCaptionDescriptionModel.class];

        NSArray *captions = [description reOrder];

        if (!captions || captions.count == 0) {

            //没有字幕就别瞎搞了

            continue;

        }

        

        FSCaptionModel *captionModel = captions.firstObject;

        UIImage *image = captionModel.image;/*将水印生成图片,采用图片方法添加水印*/

        CGFloat scaleY = captionModel.scaleY;

        CGFloat scaleHeight = captionModel.scaleHeight;

        CALayer *layer = [CALayer layer];

        layer.frame = CGRectMake(0, size.height * scaleY, size.width, size.height * scaleHeight);

        layer.contents = (__bridge id)image.CGImage;

        

        /*

         字幕动画由两个组成:

         1. 显示所有字幕<动画开始前保持,初始状态。动画时间是0.结束后不移除动画>

         2. 隐藏字幕,到最后。

         */

        CGFloat showStartTime = description.startIndex * granularity;

        CGFloat hiddenAginStartTime = showStartTime + effectSeries.count*granularity;

        

        CABasicAnimation *animation = nil;

        if (showStartTime > 0) {

            animation = [CABasicAnimation animationWithKeyPath:@"opacity"];

            animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];

            [animation setFromValue:[NSNumber numberWithFloat:0.0]];

            [animation setToValue:[NSNumber numberWithFloat:1.0]];

            [animation setBeginTime:showStartTime];

            [animation setFillMode:kCAFillModeBackwards];/*must be backwards*/

            [animation setRemovedOnCompletion:NO];/*must be no*/

            [layer addAnimation:animation forKey:@"animateOpacityShow"];

        }

        /*最后一个字幕片段不是整的1.5s或者5秒。就不隐藏动画了*/

        if (j != self.effectsArray.count-1) {

            animation = [CABasicAnimation animationWithKeyPath:@"opacity"];

            animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];

            [animation setFromValue:[NSNumber numberWithFloat:1.0]];

            [animation setToValue:[NSNumber numberWithFloat:0.0]];

            [animation setBeginTime:hiddenAginStartTime];

            [animation setRemovedOnCompletion:NO];/*must be no*/

            [animation setFillMode:kCAFillModeForwards];

            [layer addAnimation:animation forKey:@"animateOpacityHiddenAgin"];

        }

        

        [parentLayer addSublayer:layer];

    }

    

    parentLayer.geometryFlipped = YES;

    composition.animationTool = [AVVideoCompositionCoreAnimationTool

                                 videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

}

 

- (void)monitorSingleExporter:(AVAssetExportSession *)exporter{

    double delay = 1.0;

    int64_t delta = (int64_t)delay * NSEC_PER_SEC;

    dispatch_time_t poptime = dispatch_time(DISPATCH_TIME_NOW, delta);

    dispatch_after(poptime, dispatch_get_main_queue(), ^{

        if (exporter.status == AVAssetExportSessionStatusExporting) {

            NSLog(@"whole progress is %f",  exporter.progress);

            [self monitorSingleExporter:exporter];

        }

    });

}

-(AVMutableVideoCompositionLayerInstruction *) transformVideo:(AVAsset *)asset track:(AVMutableCompositionTrack *)firstTrack isVideoAssetPortrait:(void(^)(CGSize size))block{

    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:firstTrack];

    

    

    AVAssetTrack *videoAssetTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;

    BOOL isVideoAssetPortrait_  = NO;

    CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;

    if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {

        videoAssetOrientation_ = UIImageOrientationRight;

        videoTransform = CGAffineTransformMakeRotation(M_PI_2);

 

        videoTransform = CGAffineTransformTranslate(videoTransform, 0, -videoAssetTrack.naturalSize.height);

        isVideoAssetPortrait_ = YES;

    }

    if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {

        videoAssetOrientation_ =  UIImageOrientationLeft;

        //这个地方很恶心,涉及到reveal看不到的坐标系

        videoTransform = CGAffineTransformMakeRotation(-M_PI_2);

        videoTransform = CGAffineTransformTranslate(videoTransform, - videoAssetTrack.naturalSize.width, 0);

        isVideoAssetPortrait_ = YES;

    }

    if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {

        videoAssetOrientation_ =  UIImageOrientationUp;

    }

    if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {

        videoTransform = CGAffineTransformMakeRotation(-M_PI);

        videoTransform = CGAffineTransformTranslate(videoTransform, -videoAssetTrack.naturalSize.width, -videoAssetTrack.naturalSize.height);

//        videoTransform = CGAffineTransformRotate(videoTransform, M_PI/180*45);

        videoAssetOrientation_ = UIImageOrientationDown;

    }

    [videolayerInstruction setTransform:videoTransform atTime:kCMTimeZero];

    

    CGSize naturalSize;

    if(isVideoAssetPortrait_){

        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);

    } else {

        naturalSize = videoAssetTrack.naturalSize;

    }

    

    

    if(block){

        block(naturalSize);

    }

    return videolayerInstruction;

}


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版权声明:本文为CSDN博主「hherima」的原创文章,遵循CC 4.0 BY-SA版权协议,转载请附上原文出处链接及本声明。

原文链接:https://blog.csdn.net/hherima/article/details/72725395


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