用AVFoundation编写视频

我想根据我的方面撰写视频 . 用户将从库中选择视频 . 看看我的屏幕 . 有一个背景是 UIView . 它的颜色是多变的 . 并且该视图上方有一个AVPlayer . 我已根据所选视频的宽高比调整了 AVPlayer 的大小 . 现在我想编写整个场景并将其保存到照片库 . 到目前为止我已经这样做了 . 保存的视频应该像第二张图像一样 . 但它没有提供随机视频 .

- (IBAction)videoOutput:(id)sender
{
    // 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, self.videoAsset.duration) ofTrack:[[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];


    // 3.1 - Create AVMutableVideoCompositionInstruction

    AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, self.videoAsset.duration);

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

    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
    AVAssetTrack *videoAssetTrack = [[self.videoAsset 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;
        isVideoAssetPortrait_ = YES;
    }
    if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
        videoAssetOrientation_ =  UIImageOrientationLeft;
        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) {
        videoAssetOrientation_ = UIImageOrientationDown;
    }


    CGSize naturalSize;
    if(isVideoAssetPortrait_){
        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
    } else {
        naturalSize = videoAssetTrack.naturalSize;
    }
    NSLog(@"%@",NSStringFromCGSize(naturalSize));

    [videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];

    // 3.3 - Add instructions
    mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

    AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

    mainCompositionInst.renderSize = CGSizeMake(320, 320);
    mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
    mainCompositionInst.frameDuration = CMTimeMake(1, 30);

    [self applyVideoEffectsToComposition:mainCompositionInst size:naturalSize withColor:[array objectAtIndex:colorTag]];

    // 4 - Get path
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:
                             [NSString stringWithFormat:@"FinalVideo-%d.mov",arc4random() % 1000]];
    NSURL *url = [NSURL fileURLWithPath:myPathDocs];

    // 5 - Create exporter
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPreset640x480];
    exporter.outputURL=url;
    exporter.outputFileType = AVFileTypeQuickTimeMovie;
    exporter.shouldOptimizeForNetworkUse = YES;
    exporter.videoComposition = mainCompositionInst;
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            [self exportDidFinish:exporter];
        });
    }];
}

- (void)exportDidFinish:(AVAssetExportSession*)session
{
    if (session.status == AVAssetExportSessionStatusCompleted)
    {
        NSURL *outputURL = session.outputURL;
        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
        if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputURL]) {
            [library writeVideoAtPathToSavedPhotosAlbum:outputURL completionBlock:^(NSURL *assetURL, NSError *error){
                dispatch_async(dispatch_get_main_queue(), ^{
                    if (error) {
                        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Video Saving Failed"
                                                                       delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                        [alert show];
                    } else {
                        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Video Saved" message:@"Saved To Photo Album"
                                                                       delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                        [alert show];
                    }
                });
            }];
        }
    }
}

- (UIImage *)imageWithColor:(UIColor *)color rectSize:(CGRect)imageSize {
    CGRect rect = imageSize;
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
    [color setFill];
    UIRectFill(rect);   // Fill it with your color
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

- (void)applyVideoEffectsToComposition:(AVMutableVideoComposition *)composition size:(CGSize)size withColor:(UIColor *)color
{
    CGFloat temp = 1280;
    CGSize videoSize = size;
    CGFloat width = ((videoSize.width/videoSize.height)*temp);
    CGFloat x = (temp - width)/2;

    UIImage *borderImage = nil;

    borderImage = [self imageWithColor:color rectSize:CGRectMake(0, 0, size.width, size.height)];

    CALayer *backgroundLayer = [CALayer layer];
    [backgroundLayer setContents:(id)[borderImage CGImage]];
     backgroundLayer.frame = CGRectMake(0, 0, 720, 1280);
    [backgroundLayer setMasksToBounds:YES];

    CALayer *videoLayer = [CALayer layer];
    videoLayer.frame = CGRectMake(x, 0, width-00, temp);
    NSLog(@"video layer  >>  %@",NSStringFromCGRect(videoLayer.frame));
    videoLayer.contentsGravity = kCAGravityBottomRight;

    CALayer *parentLayer = [CALayer layer];
    parentLayer.frame = CGRectMake(0, 0, 720, 1280);
    parentLayer.contentsGravity = kCAGravityBottomRight;

    parentLayer.backgroundColor = [UIColor redColor].CGColor;
    [parentLayer addSublayer:backgroundLayer];
    [parentLayer addSublayer:videoLayer];

    composition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
}

- (IBAction)btn_play_pressed:(id)sender
{
    [self.player play];
}

- (void)btn_pressed:(id)sender
{
    colorTag = [(UIButton *)sender tag];
    NSLog(@" %d",colorTag);
    self.backgroundView.backgroundColor = [array objectAtIndex:colorTag];
}