ios - IOS AVFoundation - 正方形のビデオ

Question

ビデオのフォーマットを変更する良い方法は何ですか?

複数のビデオをまとめてマージし、AVAssetExportSession を使用してエクスポートするために、次のようなことを行っています。

AVMutableComposition *mixComposition = [AVMutableComposition composition];
    AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    AVMutableCompositionTrack *compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    NSError * error = nil;
    AVURLAsset *assetClip;
    AVAssetTrack *clipVideoTrack;
    AVAssetTrack *clipAudioTrack;
    for (int i = [clipPaths count]-1; i >= 0; i--) {
        assetClip = [AVURLAsset URLAssetWithURL:[clipPaths objectAtIndex:i] options:nil];
        clipVideoTrack = [[assetClip tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
        clipAudioTrack = [[assetClip tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

        [compositionVideoTrack insertTimeRange:clipVideoTrack.timeRange ofTrack:clipVideoTrack atTime:kCMTimeZero error:&error];
        [compositionAudioTrack insertTimeRange:clipAudioTrack.timeRange ofTrack:clipAudioTrack atTime:kCMTimeZero error:&error];
    } 

    NSString *cachesFolder = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingString:@"/"];
    NSString *finalPath = [cachesFolder stringByAppendingPathComponent:[self.currentFileName stringByAppendingString:@".mov"]];

    // Remove video file if it exists 
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if([fileManager fileExistsAtPath:finalPath]) {
        [fileManager removeItemAtPath:finalPath error:&error];
    }

    NSURL *lastURL = [NSURL fileURLWithPath:finalPath];

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
    exporter.outputFileType = AVFileTypeQuickTimeMovie;
    exporter.outputURL = lastURL;
    [exporter exportAsynchronouslyWithCompletionHandler:^(void){
        switch(exporter.status) {
            case AVAssetExportSessionStatusFailed:
                NSLog(@"exporting failed"); 
                break;
            case AVAssetExportSessionStatusCompleted:
                NSLog(@"exporting completed"); 
                [[NSNotificationCenter defaultCenter] postNotificationName:@"didCompleteMovieMerging" object:nil];
                break;
            case AVAssetExportSessionStatusCancelled:
                NSLog(@"export cancelled");
                break;
        }
    }];

私はあなたが使用できることを見ました

AVMutableVideoComposition* videoComposition = [AVMutableVideoComposition videoComposition];
videoComposition.renderSize = CGSizeMake(320, 320);
videoComposition.frameDuration = CMTimeMake(1, 30);

AVAssetExportSession の代わりに、これらの両方を連携させる方法が見つかりません。