xeye - combine side-by-side 3d into red/blue glasses format

main.m

// Written March 26th 2013

#import <Cocoa/Cocoa.h>
#import <AVFoundation/AVFoundation.h>

int main(int argc, char **argv) {
  NSLog(@"Hello world");

  NSError *err;

  NSURL *inURL = [NSURL fileURLWithPath:@"/Users/william/Desktop/Hobbit3d.mp4"];
  NSURL *outURL = [NSURL fileURLWithPath:@"/Users/william/Desktop/Hobbit3d.Converted.mov"];

  AVAsset *asset = [AVAsset assetWithURL:inURL];
  assert(asset);

  // Construct reader

  AVAssetReader *reader = [AVAssetReader assetReaderWithAsset:asset error:&err];
  if (!reader) { NSLog(@"Couldn't create reader: %@", err); }
  assert(reader);

  NSArray *audioTracks = [asset tracksWithMediaType:AVMediaTypeAudio];
  NSArray *videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];

  // Add audio track outputs to reader

  AVAssetReaderOutput *audioReaderOutput = [AVAssetReaderAudioMixOutput assetReaderAudioMixOutputWithAudioTracks:audioTracks audioSettings:nil];
  assert(audioReaderOutput);
  assert([reader canAddOutput:audioReaderOutput]);
  [reader addOutput:audioReaderOutput];

  // Add video track outputs to reader

  NSDictionary *videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA)};
  AVAssetReaderTrackOutput *videoReaderOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTracks[0] outputSettings:videoSettings];
  assert(videoReaderOutput);
  assert([reader canAddOutput:videoReaderOutput]);
  [reader addOutput:videoReaderOutput];

  // -----

  // Construct writer

  AVAssetWriter *writer = [AVAssetWriter assetWriterWithURL:outURL fileType:AVFileTypeQuickTimeMovie error:&err];
  if (!writer) { NSLog(@"Couldn't create writer: %@", err); }
  assert(writer);

  // Add audio track inputs to writer

  // AudioChannelLayout channelLayout;
  // memset(&channelLayout, 0, sizeof(AudioChannelLayout));
  // channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
  // NSDictionary *outputSettings = @{
  //   AVFormatIDKey: @(kAudioFormatLinearPCM),
  //   AVSampleRateKey: @44100.0,
  //   AVNumberOfChannelsKey: @2,
  //   AVChannelLayoutKey: [NSData dataWithBytes:&channelLayout length:sizeof(AudioChannelLayout)],
  //   AVLinearPCMBitDepthKey: @16,
  //   AVLinearPCMIsNonInterleaved: @NO,
  //   AVLinearPCMIsFloatKey: @NO,
  //   AVLinearPCMIsBigEndianKey: @NO
  // };

  AVAssetWriterInput *audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:nil];
  assert(audioWriterInput);
  assert([writer canAddInput:audioWriterInput]);
  [writer addInput:audioWriterInput];


  // Add video track input to writer

  // NSDictionary *videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA)};
  AVAssetWriterInput *videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:nil];
  assert(videoWriterInput);
  assert([writer canAddInput:videoWriterInput]);
  [writer addInput:videoWriterInput];


  // -----
  // Begin!

  [writer startWriting];
  [reader startReading];

  AVAssetTrack *soundTrack = audioTracks[0];
  CMTime startTime = CMTimeMake(0, soundTrack.naturalTimeScale);
  [writer startSessionAtSourceTime:startTime];


  BOOL audioFinished = NO;
  BOOL videoFinished = NO;

  int videoFrame = 0;

  @try {
    while (reader.status == AVAssetReaderStatusReading) {
      if (!audioFinished && audioWriterInput.readyForMoreMediaData) {
        CMSampleBufferRef buffer = [audioReaderOutput copyNextSampleBuffer];
        if (buffer) {
          [audioWriterInput appendSampleBuffer:buffer];
          CFRelease(buffer);
        } else {
          audioFinished = YES;
        }
      }

      if (!videoFinished && videoWriterInput.readyForMoreMediaData) {
        videoFrame ++;
        CMSampleBufferRef buffer = [videoReaderOutput copyNextSampleBuffer];
        if (buffer) {
          @autoreleasepool {

            if (videoFrame == 2000) {
              NSLog(@"Beginning effect");
            } else if (videoFrame == 3000) {
              NSLog(@"Finished with effect");
              break;
            }
            if (videoFrame > 2000 && videoFrame < 3000) {
              CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(buffer);
              CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)imageBuffer;
              CVPixelBufferLockBaseAddress(pixelBuffer, 0);

              uint8_t *pixels = CVPixelBufferGetBaseAddress(pixelBuffer);

              size_t width = CVPixelBufferGetWidth(pixelBuffer);
              size_t bpr = CVPixelBufferGetBytesPerRow(pixelBuffer);
              size_t bpp = bpr / width;
              for (int y = 0; y < CVPixelBufferGetHeight(pixelBuffer); y++) {
                for (int x = width / 2; x < width; x++) {
                  uint8_t leftB = pixels[y * bpr + x * bpp - bpp / 2 * width];
                  uint8_t leftG = pixels[y * bpr + x * bpp - bpp / 2 * width + 1];
                  uint8_t leftR = pixels[y * bpr + x * bpp - bpp / 2 * width + 2];
                  uint8_t rightB = pixels[y * bpr + x * bpp];
                  uint8_t rightG = pixels[y * bpr + x * bpp + 1];
                  uint8_t rightR = pixels[y * bpr + x * bpp + 2];

                  pixels[y * bpr + x * bpp - bpp / 2 * width] = 0;
                  pixels[y * bpr + x * bpp - bpp / 2 * width + 1] = 0;
                  pixels[y * bpr + x * bpp - bpp / 2 * width + 2] = 0;

                  pixels[y * bpr + x * bpp + 2] = (uint8_t)((0.7 * leftG) + (0.3 * leftB));
                }
              }

              CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
              [videoWriterInput appendSampleBuffer:buffer];
              CFRelease(imageBuffer);
            } else {
              [videoWriterInput appendSampleBuffer:buffer];
            }

            CFRelease(buffer);
          }
        } else {
          videoFinished = YES;
        }
      }
    }
  } @catch (NSException *ex) {
    NSLog(@"boom! %@", ex);
  }

  NSLog(@"Finishing up.");
  [writer finishWriting];
  [reader cancelReading];
  NSLog(@"Done");


  return 0;
}