Encoding and decoding of HDR video
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README.md

Luma HDRv Luma Hdrv

Project web: http://lumahdrv.org/

General

The Luma HDRv package provides libraries for encoding and decoding of HDR video sequences. The encoding is done using the high bit depth profiles of google's VP9 codec. To be able to store HDR images with the limited bits available, luminance and color transformations are done in such way to ensure that quantization errors are below the visibility threshold of the human visual system. This assumes that the input is given in physical units (cd/m^2).

For examples on how to use the libraries, please see the simple test examples in ./test.

The Luma HDRv package also provides command line applications for encoding, decoding and playback of HDR video using the libraries. The input video for encoding could either be provided as separate OpenEXR frames, or piped from pfstools. The HDR video is stored in a Matroska container, for increased flexibility and compatibility.

For further information on how to use the applications, please see the manual pages provided with each application. After installation these should be available on the system as:

$ man lumaenc
$ man lumadec
$ man lumaplay

Comparison to HDR video formats

Luma HDRv provides capabilities to encode HDR video with a number of different settings (transfer function, color space, bit depth etc.). The default settings encodes luminance between 0.005 and 10000 cd/m^2 at 11 bits by means of the perceptual quantizer (PQ, SMPTE ST 2084) function, and colors at 8 bits/channel in the Lu'v' color space.

It is also possible to encode in a format that is compatible with existing HDR video standards. The following encodes with PQ at 10 bits, and in the YCbCr color space according to recommendation ITU-R BT.2020, with luminance range limited to 0.01-1000 cd/m^2:

lumaenc \
	--input hdr_frames_%06d.exr \
	--frames 1:500 \
	--output hdr_video.mkv \
	--encoding-bitdepth 10 \
	--color-bitdepth 10 \
	--ptf-bitdepth 10 \
	--profile 2 \
	--transfer-function PQ \
	--color-space YCBCR \
	--pre-scaling 20 \
	--max-luminance 1000 \
	--min-luminance 0.01

Please see manual pages for explanation of the different parameters. Note that the --pre-scaling option can be used to approximately calibrate the input to physical units. The result of this encoding is equivalent to the HDR10 standard, which is the most widely supported HDR video format. This makes the video compatible with applications that support HDR10, and that can decode VP9 codec stored in a Matroska container. It is for example possible to upload the result to Youtube and Vimeo, where it is properly recognized as HDR video.

Included libraries and applications

Depending on what is available on the build system (see compilation and installation section), the Luma HDRv package is built with different executables. In a full build, the following parts are included:

  • libluma_encoder -- Luma HDRv encoding library, providing functionalities for encoding and writing of HDR videos.
  • libluma_decoder -- Luma HDRv decoding library, providing functionalities for decoding and reading of HDR videos.
  • lumaenc -- HDR video encoding application, for encoding HDR frames into a HDR video.
  • lumadec -- HDR video decoding application, for decoding of HDR video into separate frames.
  • lumaplay -- Simple playback of encoded HDR videos.
  • test_simple_enc -- Minimal encoding test example, to demonstrate how to use the luma_encoder library.
  • test_simple_dec -- Minimal decoding test example, to demonstrate how to use the luma_decoder library.

Compilation and installation

Compilation is provided through CMake, and should be able to detect which applications to build depending on existing dependencies.

For a minimal build, only providing the Luma HDRv libraries (libluma_encoder and libluma_decoder), there are no external dependencies. The required dependencies for these are included in the build tree and compiled together with the Luma HDRv libraries.

The provided applications are compiled if their dependencies are found. The dependencies are as follows:

UNIX

For an out-of-tree build (recommended) and install, do the following:

$ cd <path_to_luma_hdrv>
$ mkdir build
$ cd build
$ cmake ../
$ make
$ make install

WINDOWS

Since libvpx requires Cygwin to be built, this must be done before compilation of Luma HDRv. A quick guide for installation of libvpx for linking with Luma HDRv follows (please refer to instructions on the WebM webpage for more information on Windows compilation of libvpx):

  1. Extract the provided libvpx archive (lib/libvpx.tar.gz) in place, or download libvpx and put under lib/libvpx.

  2. In Cygwin, go to the build directory of libvpx and build a Visual Studio solution:

    $ cd /cygdrive/<path_to_luma_hdrv>/lib/libvpx/build
    $ ../configure --enable-vp9-highbitdepth --enable-vp9 --enable-multithread
        --as=yasm --disable-avx2 --disable-libyuv --disable-webm_io
        --disable-unit_tests --disable-install-docs --disable-install-bins
        --disable-install-srcs --disable-examples --disable-docs --disable-vp8
        --target=x86-win32-vs10 --enable-static-msvcrt
    $ make
    

    The --target option should be replaced with the appropriate platform and Visual Studio version.

  3. Download the Yasm assembler executable (yasm-x.x.x-win32.exe or yasm-x.x.x-win64.exe), rename it to yasm.exe and place it in the build directory (lib/libvpx/build/), or any directory known by Visual Studio.

  4. Build the VPX Visual Studio solution, and place the compiled library (vpxmt.lib) either in the build directory of Luma HDRv or in the lib folder in the build directory.

  5. Run CMake for Luma HDRv. It should be able to detect VPX library that has been created, and the include files in lib/libvpx/.

  6. Build Luma HDRv Visual Studio solution, and then run the INSTALL project in the solution to install Luma HDRv.

Included libraries

Minimal dependencies are included as is in ./lib, and with no alterations. These can easily be replaced by other versions of the libraries, simply by replacing the source files and recompiling Luma HDRv. The included libraries are:

Please see the respective source directories in ./lib for license information.

Known issues

The library does not work with libvpx3 provided in Ubuntu 16.04. Uninstall libvpx-dev and compile with the static version of libvpx (provided in lib, and automatically used if libvpx cannot be found in the system).

License

Copyright (c) 2015, The LumaHDRv authors. All rights reserved.

Luma HDRv is distributed under a BSD license. See LICENSE for information.

Luma HDRv