IOS How to convert resize and quanlity movie

/* Convert resize and quanlity movie */
+ (void) resizeVideo:(NSString*)inputVideo output:(NSString*) outputVideo size:(CGSize) size bitsPerPixel:(float) bitsPerPixel {
    NSAutoreleasePool *pools = [[NSAutoreleasePool alloc] init];
    NSURL *outPath = [NSURL fileURLWithPath:outputVideo];
    NSURL *inputPath = [NSURL fileURLWithPath:inputVideo];
    NSError *error = nil;   
    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:outPath fileType:AVFileTypeQuickTimeMovie error:&error];
    NSParameterAssert(videoWriter);
    AVAsset *avAsset = [[[AVURLAsset alloc] initWithURL:inputPath options:nil] autorelease];
   
    int numPixels = size.width * size.height;
    NSLog(@"bitsPerPixel:%f",bitsPerPixel);
    int bitsPerSecond = numPixels * bitsPerPixel;
   
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInteger:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInteger:size.height], AVVideoHeightKey,
                                   [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSNumber numberWithInteger:bitsPerSecond], AVVideoAverageBitRateKey,
                                    [NSNumber numberWithInteger:30], AVVideoMaxKeyFrameIntervalKey,
                                    nil], AVVideoCompressionPropertiesKey,
                                   nil];
   
    AVAssetWriterInput* videoWriterInput = [[AVAssetWriterInput
                                             assetWriterInputWithMediaType:AVMediaTypeVideo
                                             outputSettings:videoSettings] retain];
    NSParameterAssert(videoWriterInput);
    NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
    videoWriterInput.expectsMediaDataInRealTime = YES;
    [videoWriter addInput:videoWriterInput];
    NSError *aerror = nil;
    AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:avAsset error:&aerror];
    AVAssetTrack *videoTrack = [[avAsset tracksWithMediaType:AVMediaTypeVideo]objectAtIndex:0];
    videoWriterInput.transform = CGAffineTransformRotate(videoTrack.preferredTransform, DEGREES_TO_RADIANS(180));//videoTrack.preferredTransform;
    NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
    AVAssetReaderTrackOutput *asset_reader_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:videoOptions];
    [reader addOutput:asset_reader_output];
   
    /* Begin convert */
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];
    [reader startReading];
    dispatch_queue_t _processingQueue = dispatch_queue_create("assetAudioWriterQueue", NULL);
    [videoWriterInput requestMediaDataWhenReadyOnQueue:_processingQueue usingBlock:
     ^{
         while ([videoWriterInput isReadyForMoreMediaData]) {
             CMSampleBufferRef sampleBuffer;
             if ([reader status] == AVAssetReaderStatusReading &&
                 (sampleBuffer = [asset_reader_output copyNextSampleBuffer])) {
                
                 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
                 BOOL result = [videoWriterInput appendSampleBuffer:sampleBuffer];
                 CMSampleBufferInvalidate(sampleBuffer);
                 CFRelease(sampleBuffer);
                 sampleBuffer = nil;
                 if (!result) {
                     [reader cancelReading];
                     break;
                 }
                 [pool release];
             } else {
                 [videoWriterInput markAsFinished];
                
                 switch ([reader status]) {
                     case AVAssetReaderStatusReading:
                         // the reader has more for other tracks, even if this one is done
                         break;
                        
                     case AVAssetReaderStatusCompleted:
                         [videoWriter finishWriting];
                         [videoWriter release];
                         [videoWriterInput release];
                         [asset_reader_output release];
                         break;
                     case AVAssetReaderStatusFailed:
                         [videoWriter cancelWriting];
                         [videoWriter release];
                         [videoWriterInput release];
                         [asset_reader_output release];
                         break;
                 }
                
                 break;
             }
         }
     }
     ];
   
    [pools release];
}