QTKit - 合并两个具有不同宽度和高度的视频？

我刚刚制作了一个简单的应用程序，它使用 QTKit 将两个视频合并在一起

这里是problem:

我刚刚发现，如果我尝试合并两个宽度和高度不同的视频，输出的视频的高度和宽度与大视频相同，但包含带有黑色和宽边框的小视频。

问题：

如何将两个视频合并在一起并获得具有正确格式（宽度/高度）的输出视频？

更好地理解我需要什么的示例：

我有两个视频：

视频 1 = 1920 x 1280 视频 2 = 1280 x 960

我想要的： 1920 x 1280 的视频（需要放大并裁剪小视频）

Code:

-(void)voidMethodToCombine {


NSError *err = nil;
QTMovie *myCombinedMovie = [[QTMovie alloc] initToWritableData:[NSMutableData data] error:&err];
if (err)
{
    NSRunAlertPanel(@"Errore nella creazione del video",[err localizedDescription], nil, @"Chiudi", nil, nil);
    return;
    return;
}


// Create the File Open Dialog class.
NSSavePanel *savePanel = [NSSavePanel savePanel]; //Dove salvo il video ?


if ([savePanel runModal])//Se premo ok
{   
    [indicatore setUsesThreadedAnimation:YES];
    [indicatore startAnimation:self];
    NSURL *saveURL = savePanel.URL;
    NSString *savePath = [saveURL path];
//Prelevo i 2 percorsi e gli inserisco negli array

NSString *video1 = [URLVideo1 stringValue];
NSString *video2 = [URLVideo2 stringValue];

NSURL *theURLvideo1 = [NSURL fileURLWithPath:video1];

NSURL *theURLvideo2 = [NSURL fileURLWithPath:video2];

if((theURLvideo1) && (theURLvideo2)) {



NSArray *myMovieURLs = [NSArray arrayWithObjects:theURLvideo1,theURLvideo2, nil];

for (NSURL *url in myMovieURLs)
{
    QTMovie *theMovie = [QTMovie movieWithURL:url error:&err];
    if (err){
        NSRunAlertPanel(@"Errore durante il caricamento di uno dei film",[err localizedDescription], nil, @"Chiudi", nil, nil);
        return;
    }
    QTTimeRange timeRange = QTMakeTimeRange(QTZeroTime, [theMovie duration]);
    QTTime insertionTime = [myCombinedMovie duration]; 
    [myCombinedMovie insertSegmentOfMovie:theMovie timeRange:timeRange atTime:insertionTime];
}

NSDictionary *writeAttributes = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], QTMovieFlatten, nil]; 
//Pannello di path salvataggio

bool success = [myCombinedMovie writeToFile:savePath withAttributes:writeAttributes error:&err];




[indicatore stopAnimation:self];
NSBeep();
NSString *dove = [[NSString alloc] initWithFormat:@"Video esportato in:\n%@",savePath];
NSRunAlertPanel(@"Esportazione avvenuta con successo!", dove, @"Ok", nil, nil);

if (!success)
{
    NSRunAlertPanel(@"Errore durante il salvataggio del video.",[err localizedDescription], nil, @"Chiudi", nil, nil);
    return;
    return;
}
}
//Se non esiste alcun percorso
else {

    NSRunAlertPanel(@"Impossibile selezionare i file.", @"Controlla di aver specificato un percorso.", @"Chiudi", nil, nil);
}

要做到这一点，最简单的方法是使用 AVFoundation 框架而不是 QTKit，因为编辑/操作视频要容易得多（imo），尽管它似乎有点慢并且代码可能不太紧凑。

我建议首先阅读 AVFoundation 编程指南：https://developer.apple.com/library/mac/documentation/AudioVideo/Conceptual/AVFoundationPG/AVFoundationPG.pdf

但这里有一个可以帮助您入门的基本示例。在开始之前，请确保您已链接到 AVFoundation 和 CoreMedia 框架。

在您的标头中，除了您可能添加的任何其他方法或 ivars 之外AVAssetExportSession *exporter and NSTimer *timer，以及一种方法- (void) monitorProgress;.

然后，您的实现文件将包含以下方法（假设您使用名为 doIt 的 IBAction 触发该方法）。并且不要忘记#import <AVFoundation/ AVFoundation.h> and #import <CoreMedia/CoreMedia.h>:

- (IBAction)doIt:(id)sender {
// Initial array of movie URLs
NSArray *myMovieURLs = [NSArray arrayWithObjects:[NSURL fileURLWithPath:@"/path/to/first.mov"], [NSURL fileURLWithPath:@"/path/to/second.mov"], nil];

// Create the composition & A/V tracks
AVMutableComposition *comp = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [comp addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *compositionAudioTrack = [comp addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

// A reference for insertion start time
CMTime startTime = kCMTimeZero;

for (int i=0; i< [myMovieURLs count]; i++){
    // Get asset 
    NSURL *movieURL = [myMovieURLs objectAtIndex:i];
    AVURLAsset *asset = [AVURLAsset URLAssetWithURL:movieURL options:nil];

    // Get video and audio tracks (assuming video exists - test for audio as an empty track will crash the program!) and insert in composition tracks
    AVAssetTrack *videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    bool success = [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:videoTrack atTime:startTime error:nil];

    if ([[asset tracksWithMediaType:AVMediaTypeAudio]count]){
        AVAssetTrack *audioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
        success = [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:audioTrack atTime:startTime error:nil];
    }

    // increment the start time to the end of this first video
    startTime = CMTimeAdd(startTime, [asset duration]);
}

//Set the output URL
NSURL *outputURL = [NSURL fileURLWithPath:@"/path/to/output.mov"];

/* Create the exporter.  
 Note the preset type is up to you to choose.  If you wanted, you could check the asset's size (with [asset naturalSize]) or other values above and use that to base your preset on. 
 Use exportPresetsCompatibleWithAsset: to get a list of presets that are compatible with a specific asset.
 */
NSLog(@"Compat presets you could use: %@", [AVAssetExportSession exportPresetsCompatibleWithAsset:comp]);
exporter = [[AVAssetExportSession alloc] initWithAsset:comp presetName:AVAssetExportPreset640x480];

[exporter setOutputURL:outputURL];
[exporter setOutputFileType:AVFileTypeQuickTimeMovie];
[exporter exportAsynchronouslyWithCompletionHandler:^(void){
    switch ([exporter status]) {
        case AVAssetExportSessionStatusFailed:
            NSLog(@"Export failed: %@", [[exporter error] localizedDescription]);
            break;
        case AVAssetExportSessionStatusCancelled:
            NSLog(@"Export canceled");
            break;
        default:
            break;
    }
}];

// This is just a simple timer that will call a method to log the progress
timer=[NSTimer scheduledTimerWithTimeInterval:5
                                       target:self
                                     selector:@selector(monitorProgress)
                                     userInfo:nil
                                      repeats:YES];
}



-(void)monitorProgress{ 
if ([exporter progress] == 1.0){
    [timer invalidate];
}

NSLog(@"Progress: %f",[exporter progress]* 100);

}