iPhone:以编程方式压缩录制的视频以进行共享？

Question

在录制视频之前调用相机 View 时，我实现了覆盖 View 。

pickerController.cameraOverlayView =myOverlay;

视频录制以及录制视频后将视频保存到相册并通过电子邮件等共享，一切正常。

如果我将视频质量设置为“高质量”，则录制的视频会变得很大。例如，如果我录制 30 秒的高质量视频，则录制的视频大约为 30 - 40 mb。

pickerController.videoQuality = UIImagePickerControllerQualityTypeHigh;

如何编程在共享之前压缩高质量录制的视频，就像 Apple 使用内置视频录像机所做的那样？

请指导我解决这个问题。

谢谢!

更新:

这是我最近尝试的，但仍然没有成功:我想压缩拍摄到 didFinishPickingMediaWithInfo 的录制视频并将其存储在同一个相册中实际视频路径本身，而不是其他任何地方。我测试了当我从照片库中选取时，相同的视频被压缩到非常小的尺寸，但从相机拍摄并通过 didFinishPickingMediaWithInfo 获得的相同视频未压缩，尽管我使用了下面的 AVAssetExportSession 代码。

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{

    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];


if ([mediaType isEqualToString:(NSString *)kUTTypeMovie])
{

    NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL];
    NSString *urlPath = [videoURL path];

    if ([[urlPath lastPathComponent] isEqualToString:@"capturedvideo.MOV"])
    {
        if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum (urlPath))
        {
            [self copyTempVideoToMediaLibrary :urlPath];


        }
        else
        {
            NSLog(@"Video Capture Error: Captured video cannot be saved...didFinishPickingMediaWithInfo()");                
        }
    }       
    else
    {
        NSLog(@"Processing soon to saved photos album...else loop of lastPathComponent..didFinishPickingMediaWithInfo()");
    }
}    
[self dismissModalViewControllerAnimated:YES];
}

- (void)copyTempVideoToMediaLibrary :(NSString *)videoURL {

        dispatch_queue_t mainQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(mainQueue, ^{

    ALAssetsLibrary *library = [[[ALAssetsLibrary alloc] init] autorelease];

    ALAssetsLibraryWriteVideoCompletionBlock completionBlock = ^(NSURL *assetURL, NSError *error) {
        NSLog(@"Saved URL: %@", assetURL);
        NSLog(@"Error: %@", error);

        if (assetURL != nil) {

            AVURLAsset *theAsset = [AVURLAsset URLAssetWithURL:[NSURL URLWithString:videoURL] options:nil];

            NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:theAsset];

            AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:theAsset presetName:AVAssetExportPresetLowQuality];

            [exportSession setOutputURL:[NSURL URLWithString:videoURL]];
            [exportSession setOutputFileType:AVFileTypeQuickTimeMovie];

            [exportSession exportAsynchronouslyWithCompletionHandler:^ {
                switch ([exportSession status]) {
                    case AVAssetExportSessionStatusFailed:
                        NSLog(@"Export session faied with error: %@", [exportSession error]);
                        break;
                    default:
                        //[self mediaIsReady];
                        break;
                }
            }];
        }
    };

    [library writeVideoAtPathToSavedPhotosAlbum:[NSURL URLWithString:videoURL] completionBlock:completionBlock];
});
}

Answer 1

如果您想压缩视频以进行远程共享并在 iPhone 上的本地存储中保持原始质量，您应该查看 AVAssetExportSession或AVAssetWriter .

另请阅读 iOS 如何管理 Assets .

- (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL 
                                   outputURL:(NSURL*)outputURL 
                                     handler:(void (^)(AVAssetExportSession*))handler
{
    [[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];
    AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
    exportSession.outputURL = outputURL;
    exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    [exportSession exportAsynchronouslyWithCompletionHandler:^(void) 
    {
        handler(exportSession);
        [exportSession release];
    }];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info

{   
    NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL];
    NSURL *outputURL = [NSURL fileURLWithPath:@"/Users/josh/Desktop/output.mov"];
    [self convertVideoToLowQuailtyWithInputURL:videoURL outputURL:outputURL handler:^(AVAssetExportSession *exportSession)
     {
         if (exportSession.status == AVAssetExportSessionStatusCompleted)
         {
             printf("completed\n");
         }
         else
         {
             printf("error\n");

         }
     }];

}