Live Stitching

Paper

Please cite this paper for the video stitcher:

M. Atokari, M. Viitanen, A. Mercat, E. Kattainen, and J. Vanne, “Parallax-tolerant 360 live video stitcher,” in Proc. IEEE Int. Conf. Visual Comm. and Image Proc., Sydney, Australia, Dec. 2019.

Or in BibTex:

@inproceedings{Atokari2019,
  author={M. {Atokari} and M. {Viitanen} and A. {Mercat} and E. {Kattainen} and J. {Vanne}},
  booktitle={2019 IEEE Visual Communications and Image Processing (VCIP)},
  title={Parallax-Tolerant 360 Live Video Stitcher},
  year={2019},
  location = {Sydney, Australia},
  doi={10.1109/VCIP47243.2019.8965900},
}

Building

Requirements

• CUDA
• Custom OpenCV (Included in the directory)
  • Custom OpenCV has some changes in stitching module
• Eigen
• Kvazaar

CUDA

• Install CUDA
  • Windows: https://docs.nvidia.com/cuda/cuda-installation-guide-microsoft-windows/index.html
    • copy the cuda lib and include folders to $(ProjectDir)
  • Linux: https://docs.nvidia.com/cuda/cuda-installation-guide-linux/index.html

OpenCV

• Make visual studio project with cmake from $(ProjectDir)../sources to $(ProjectDir)../opencv_build
• set WITH_CUDA flag true and CUDA_HOST_COMPILER to the path where your visual c compiler is. (VSINSTALLFOLDER/VC/Tools/MSVC/VERSIONNUMBER/bin/Hostx64/x64/cl.exe)
• In visual studio build the project "INSTALL"
• On linux run following commands starting in base folder

  sudo apt install libgtk2.0-dev pkg-config ffmpeg libavcodec-dev libavformat-dev libavdevice-dev
  mkdir opencv_build
  cd opencv_build
  cmake -DCMAKE_CXX_COMPILER=g++ -DCMAKE_C_COMPILER=gcc -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D WITH_CUDA=ON -D ENABLE_FAST_MATH=1 -D CUDA_FAST_MATH=1 -D WITH_CUBLAS=1 -D WITH_PNG=OFF -DBUILD_opencv_cudacodec=OFF ../sources/
  make -j8
  sudo make install

Eigen

• Windows:
  • Download Eigen and copy the Eigen folder to $(ProjectDir)include
    • http://eigen.tuxfamily.org/index.php?title=Main_Page
• Linux:
  • run following commands in base folder

    git clone https://github.com/eigenteam/eigen-git-mirror
    cp -r eigen-git-mirror/Eigen 360_stitcher

Kvazaar

https://gitlab.tut.fi/TIE/ultravideo/kvazaar#compiling-kvazaar

Building and running on Linux

After building custom OpenCV and before building 360_stitcher, make symbolic link from CUDA lib directory (most likely /usr/local/cuda/lib64) to /usr:

sudo ln -s /usr/local/cuda/lib64 /usr

If the stitcher complains about not finding shared libraries (f.ex. libopencv_core), run ldconfig

sudo ldconfig

After that the build should work:

cd 360_stitcher
make
cd build
./stitcher

Flags

• string base: Name of the folder where to search for input videos
• int skip_frames: Amount frames to skip from start of all video streams
• int offsets: Amount frames to skip from start of each video stream individually. (Use calibrate.py to get required offsets)
• bool wrapAround: If true input streams wrap around 360 degrees
• bool recalibrate: If true recalibrate the CPW mesh periodically.
• bool enable_local: If true enable content preserving warping
• bool save_video: If true save the stitched video to a file
• bool show_out: If true use imshow
• bool use_stream: If true use network streams as input. If false use video streams
• bool clear_buffers: If true, clear all frame buffers between threads before pushing more data. Not really needed, only slows the program down.
• bool debug_stream: If true show the input from network streams directly
• bool use_surf: If true use SURF to find features. If false use ORB instead. ORB is faster but SURF gives way better features
• bool send_results: If true, send the result to the player on PLAYER_ADDRESS, using PLAYER_TCP_PORT (defaults are localhost, 55555)
• bool send_height_info: If true and send_results is true, the height of the result image is sent to the player first. If send_results is false, this is ignored.
• bool keep_aspect_ratio: If true, keep the aspect ratio of the image when resizing to the final size. Otherwise stretch the image to fit the output size.
• bool add_black_bars: If true and keep_aspect_ratio is true, black bars are added above and below the image to fit the output size. If keep_aspect_ratio is false, this is ignored.
• int NUM_IMAGES: Amount of video or network streams to stitch together
• unsigned char clientAddrStart: Smallest value of the capture board IP's last octet. The boards have consecutive addresses (by default 10.21.25.41, ... , 10.21.25.46, i.e. clientAddrStart = 41). This is used so that every board is in the same position every time, and the video streams are always in the correct order.
• int OUTPUT_WIDTH, OUTPUT_HEIGHT: Dimensions of the output image. If keep_aspect_ratio is true and add_black_bars is false, the final output height may be smaller than this. Only the width of the output is guaranteed to always have this value.
• unsigned int RESULTS_MAX_SIZE: Max size of the results queue, 0 means no limit. This is meant to avoid memory overflow if the frames are produced faster than consumed. However, checking the size every time slows the program down, so 0 is the fastest setting.
• int RECALIB_DEL: Amount of frames inbetween recalibration
• double WORK_MEGAPIX: Size of images for feature finding and mesh warping
• double SEAM_MEGAPIX: Size of used seam masks
• double COMPOSE_MEGAPIX: Size of images when stitching
• float MATCH_CONF: Minimum confidence when matching SURF features
• int HESS_THRESH, NOCTAVES, NOCTAVES_LAYERS: Parameters for SURF feature finding
• int MAX_FEATURES_PER_IMAGE: Limit of features used per pair of images when optimizing CPW mesh
• bool VISUALIZE_MATCHES: Visualize feature matches in image pairs. It is a bit broken for images wrapping around border.
• bool VISUALIZE_WARPED: Visualize the CPW mesh
• int N, M: Size of the used mesh by CPW
• float ALPHAS[3]: Weights for different cost functions in CPW
• int GLOBAL_DIST: Max distance of a feature in global cost function in CPW