ios中的视频录制问题

Question

I am working on a Video making app.
In that I need to record a video in first View and after that display in second View.
For recording a video I followed this tutorial. In that I have made some changes as per my need in didFinishRecordingToOutputFileAtURL method.

Here is my updated method.

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error
{
    NSLog(@"didFinishRecordingToOutputFileAtURL - enter");

    BOOL RecordedSuccessfully = YES;
    if ([error code] != noErr)
    {
        // A problem occurred: Find out if the recording was successful.
        id value = [[error userInfo] objectForKey:AVErrorRecordingSuccessfullyFinishedKey];
        if (value)
        {
            RecordedSuccessfully = [value boolValue];
        }
    }
    else {
        NSLog(@"didFinishRecordingToOutputFileAtURL error:%@",error);
    }
    if (RecordedSuccessfully)
    {
        //----- RECORDED SUCESSFULLY -----
        NSLog(@"didFinishRecordingToOutputFileAtURL - success");
        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
        if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputFileURL])
        {
            AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];
            AVMutableCompositionTrack *track = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

            AVAsset *asset = [AVAsset assetWithURL:outputFileURL];

            [track insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:CMTimeMake(0, 1) error:nil];

            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];
            NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:
                                     [NSString stringWithFormat:@"%@%d.mov",NSBundle.mainBundle.infoDictionary[@"CFBundleExecutable"],++videoCounter]];
            [[NSFileManager defaultManager] removeItemAtPath:myPathDocs error:nil];

            NSURL *url = [NSURL fileURLWithPath:myPathDocs];

            AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
            instruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);

            AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:track];
            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;
                isVideoAssetPortrait_ = YES;
                if ([[[NSUserDefaults standardUserDefaults] stringForKey:@"orientation"] isEqualToString:@"landscape"]) {
                    videoAssetOrientation_ =  UIImageOrientationUp;
                }
            }
            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;
            }

            float renderWidth, renderHeight;
            if (![self.ratioLabel.text isEqualToString:@"16:9"]) {
                renderWidth = naturalSize.width;
                renderHeight = naturalSize.width;
                NSLog(@"Video:: width=%f height=%f",naturalSize.width,naturalSize.height);
            }
            else {
                renderWidth = naturalSize.width;
                renderHeight = naturalSize.height;
                NSLog(@"Video:: width=%f height=%f",naturalSize.width,naturalSize.height);
            }
            if (![self.ratioLabel.text isEqualToString:@"16:9"])
            {
                CGAffineTransform t1 = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.height, -(videoAssetTrack.naturalSize.width - videoAssetTrack.naturalSize.height) /2);
                CGAffineTransform t2 = CGAffineTransformRotate(t1, M_PI_2);
                [layerInstruction setTransform:t2 atTime:kCMTimeZero];
            }
            else
            {
                CGAffineTransform t2 = CGAffineTransformMakeRotation( M_PI_2);
                [layerInstruction setTransform:t2 atTime:kCMTimeZero];
            }

            AVCaptureDevicePosition position = [[VideoInputDevice device] position];
            if (position == AVCaptureDevicePositionFront)
            {
                /* For front camera only */
                CGAffineTransform t = CGAffineTransformMakeScale(-1.0f, 1.0f);
                t = CGAffineTransformTranslate(t, -videoAssetTrack.naturalSize.width, 0);
                t = CGAffineTransformRotate(t, (DEGREES_TO_RADIANS(90.0)));
                t = CGAffineTransformTranslate(t, 0.0f, -videoAssetTrack.naturalSize.width);
                [layerInstruction setTransform:t atTime:kCMTimeZero];
                /* For front camera only */
            }

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

            instruction.layerInstructions = [NSArray arrayWithObjects:layerInstruction,nil];

            AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];


            mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
            mainCompositionInst.instructions = [NSArray arrayWithObject:instruction];
            mainCompositionInst.frameDuration = CMTimeMake(1, 30);

            AVAssetExportSession *exporter;
            exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPreset1280x720];
            exporter.videoComposition = mainCompositionInst;
            exporter.outputURL=url;
            exporter.outputFileType = AVFileTypeQuickTimeMovie;
            exporter.shouldOptimizeForNetworkUse = YES;

            [exporter exportAsynchronouslyWithCompletionHandler:^{
                dispatch_async(dispatch_get_main_queue(), ^{
                    self.doneButton.userInteractionEnabled = YES;
                    if(videoAddr==nil)
                    {
                        videoAddr = [[NSMutableArray alloc] init];
                    }
                    [videoAddr addObject:exporter.outputURL];
                    [[PreviewLayer connection] setEnabled:YES];
                    AVAsset *asset = [AVAsset assetWithURL:exporter.outputURL];
                    NSLog(@"remaining seconds before:%f",lastSecond);
                    double assetDuration = CMTimeGetSeconds(asset.duration);
                    if (assetDuration>3.0)
                        assetDuration = 3.0;
                    lastSecond = lastSecond- assetDuration;
                    NSLog(@"remaining seconds after:%f",lastSecond);
                    self.secondsLabel.text = [NSString stringWithFormat:@"%0.1fs",lastSecond];
                    self.secondsLabel.hidden = NO;
                    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:videoAddr];

                    [[NSUserDefaults standardUserDefaults] setObject:data forKey:@"videoAddr"];
                    [[NSUserDefaults standardUserDefaults] synchronize];
                    videoURL = outputFileURL;
                    flagAutorotate = NO;
                    self.cancelButton.hidden = self.doneButton.hidden = NO;
                    imgCancel.hidden = imgDone.hidden = NO;
                    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"Vibration"])
                        AudioServicesPlayAlertSound(kSystemSoundID_Vibrate);
                    [[UIApplication sharedApplication] endIgnoringInteractionEvents];
                });
            }];
        }
        else {
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:[NSString stringWithFormat:@"Video can not be saved\nPlease free some storage space"] delegate:self cancelButtonTitle:nil otherButtonTitles:nil, nil];
            [alert show];
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                [alert dismissWithClickedButtonIndex:0 animated:YES];
            });
        }

    }
}

But here Is the issue.
Video is not being recorded exactly shown in preview. See these 2 screenShots.

Video recording preview


Video Playing View

Answer 1

The reason is because your iPad screen aspect ratio is not the same as camera aspect ratio.

You can modify camera preview size by setting videoGravity property of AVCaptureVideoPreviewLayer , which influences how content is viewed relative to the layer bounds:

layer.videoGravity = AVLayerVideoGravityResizeAspect;

But in that case preview won't be fullscreen.

If you want the video with the same aspect ratio as on preview fullscreen, you will have to crop it. Cropping process explained here:

Exporting AVCaptureSession video in a size that matches the preview layer

Video capture with 1:1 aspect ratio in iOS