ios - 将视频保存到 DocumentsDirectory

Question

我正在尝试通过编写 Objective c 来提高自己，但我还不足以解决这个问题。我正在使用下面的代码将视频与音频合并并将最终视频保存到相机胶卷。代码工作完美，但我需要的是将该视频保存到临时文档中，以便我可以更改或修改视频，而无需每次进行小更改时都保存它。

这是我的代码:

- (IBAction)addBackgroundMusicAction:(UIButton *)sender {
    if (self.asset == nil) {
        return;
    }


    NSString *outPutPath = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"mergeVideo-%d.mov",arc4random() % 1000]];

    NSURL *outPutUrl = [NSURL fileURLWithPath:outPutPath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:outPutPath])
    {
        [[NSFileManager defaultManager] removeItemAtPath:outPutPath error:nil];
    }
    AVMutableComposition *composition = [AVMutableComposition composition];
    CMTimeRange videoTimeRange = CMTimeRangeMake(kCMTimeZero, self.asset.duration);
    AVMutableCompositionTrack *videoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

    AVAssetTrack *videoAssetTrack = [[self.asset tracksWithMediaType:AVMediaTypeVideo] firstObject];
    [videoTrack insertTimeRange:videoTimeRange ofTrack:videoAssetTrack atTime:kCMTimeZero error:nil];

    AVURLAsset *audioAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"myAudio" ofType:@"mp3"]] options:nil];
    AVMutableCompositionTrack *audioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    AVAssetTrack *audioAssetTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] firstObject];
    [audioTrack insertTimeRange:videoTimeRange ofTrack:audioAssetTrack atTime:kCMTimeZero error:nil];


    // 3.1 - Create AVMutableVideoCompositionInstruction
    AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, self.asset.duration);
    // 3.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
    AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
    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;
    }
    [videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
    [videolayerInstruction setOpacity:0.0 atTime:self.asset.duration];

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

    AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

    CGSize naturalSize;
    if(isVideoAssetPortrait_){
        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
    } else {
        naturalSize = videoAssetTrack.naturalSize;
    }

    float renderWidth, renderHeight;
    renderWidth = naturalSize.width;
    renderHeight = naturalSize.height;
    mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
    mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
    mainCompositionInst.frameDuration = CMTimeMake(1, 30);


    AVAssetExportSession * assetExport = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality];
    assetExport.outputURL = outPutUrl;
    assetExport.outputFileType = AVFileTypeQuickTimeMovie;
    assetExport.shouldOptimizeForNetworkUse = YES;
    assetExport.videoComposition = mainCompositionInst;
    [assetExport exportAsynchronouslyWithCompletionHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            [self exportDidFinish:assetExport];
        });
    }];
}

她是我将视频导出到相机胶卷的地方:

- (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 {
                        AVPlayerItem * playeritem = [AVPlayerItem playerItemWithURL:outputURL];
                        [_player replaceCurrentItemWithPlayerItem:playeritem];
                        [_player play];

                    }
                });
            }];
        }
    }
}

正如我所说，我不需要将视频保存到相机胶卷中，我只需要将其临时保存。当我按下另一个按钮时，我还需要加载该视频。保存该视频并再次加载。

谢谢

Answer 1

使用以下代码:

 NSData *videoData = [NSData dataWithContentsOfURL:outputURL];
    if (videoData) {
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"MyFolder"];
        // Create folder if needed
        [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:YES attributes:nil error:nil];

        NSString *filePath = [dataPath stringByAppendingPathComponent:@"test.mp4"];
        if ([videoData writeToFile:filePath atomically:YES]) {
            // yeah - file written
        } else {
            // oops - file not written
        }
    } else {
        // oops - couldn't get data
    }