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Short Description
Kvazaar is an open-source HEVC encoder licensed under LGPLv2.1
Full Description


An open-source HEVC encoder licensed under LGPLv2.1

Join channel #kvazaar_hevc in Freenode IRC network to contact us.

Kvazaar is still under development. Speed and RD-quality will continue to improve. for more information.

  • Linux/Mac
  • Windows

Using Kvazaar


kvazaar --input BQMall_832x480_60.yuv --output out.hevc

The mandatory parameters are input and output. If the resolution of the input file is not in the filename, or when pipe is used, the input resolution must also be given: --input-res=1920x1080.

The default input format is 8-bit yuv420p for 8-bit and yuv420p10le for 10-bit. Input format and bitdepth can be selected with --input-format and --input-bitdepth.

Speed and compression quality can be selected with --preset, or by setting the options manually.


kvazaar -i <input> --input-res <width>x<height> -o <output>

  -i, --input                : Input file
      --input-res <res>      : Input resolution [auto]
                               auto: detect from file name
                               <int>x<int>: width times height
  -o, --output               : Output file

      --preset=<preset>      : Set options to a preset [medium]
                                   - ultrafast, superfast, veryfast, faster,
                                     fast, medium, slow, slower, veryslow

  -n, --frames <integer>     : Number of frames to code [all]
      --seek <integer>       : First frame to code [0]
      --input-fps <num>/<denom> : Framerate of the input video [25.0]
      --source-scan-type <string> : Set source scan type [progressive].
                                   - progressive: progressive scan
                                   - tff: top field first
                                   - bff: bottom field first
      --input-format         : P420 or P400
      --input-bitdepth       : 8-16
      --loop-input           : Re-read input file forever

      --help                 : Print this help message and exit
      --version              : Print version information and exit
      --aud                  : Use access unit delimiters
      --debug <string>       : Output encoders reconstruction.
      --cpuid <integer>      : Disable runtime cpu optimizations with value 0.
      --hash                 : Decoded picture hash [checksum]
                                   - none: 0 bytes
                                   - checksum: 18 bytes
                                   - md5: 56 bytes
      --no-psnr              : Don't calculate PSNR for frames
      --no-info              : Don't add encoder info SEI.

Video structure:
  -q, --qp <integer>         : Quantization Parameter [32]
  -p, --period <integer>     : Period of intra pictures [0]
                               - 0: only first picture is intra
                               - 1: all pictures are intra
                               - 2-N: every Nth picture is intra
      --vps-period <integer> : Specify how often the video parameter set is
                               re-sent. [0]
                                   - 0: only send VPS with the first frame
                                   - N: send VPS with every Nth intra frame
  -r, --ref <integer>        : Reference frames, range 1..15 [3]
      --gop <string>         : Definition of GOP structure [0]
                                   - 0: disabled
                                   - 8: B-frame pyramid of length 8
                                   - lp-<string>: lp-gop definition
                                         (e.g. lp-g8d4t2, see README)
      --cqmfile <string>     : Custom Quantization Matrices from a file
      --bitrate <integer>    : Target bitrate. [0]
                                   - 0: disable rate-control
                                   - N: target N bits per second
      --lossless             : Use lossless coding
      --mv-constraint        : Constrain movement vectors
                                   - none: no constraint
                                   - frametile: constrain within the tile
                                   - frametilemargin: constrain even more
      --roi <string>         : Use a delta QP map for region of interest
                                   Read an array of delta QP values from
                                   a file, where the first two values are the
                                   width and height, followed by width*height
                                   delta QP values in raster order.
                                   The delta QP map can be any size or aspect
                                   ratio, and will be mapped to LCU's.
      --(no-)erp-aqp         : Use adaptive QP for 360 video with
                               equirectangular projection

Compression tools:
      --deblock [<beta:tc>]  : Deblocking
                                     - beta: between -6 and 6
                                     - tc: between -6 and 6
      --(no-)sao             : Sample Adaptive Offset
      --(no-)rdoq            : Rate-Distortion Optimized Quantization
      --(no-)signhide        : Sign Hiding
      --(no-)smp             : Symmetric Motion Partition
      --(no-)amp             : Asymmetric Motion Partition
      --rd <integer>         : Intra mode search complexity
                                   - 0: skip intra if inter is good enough
                                   - 1: rough intra mode search with SATD
                                   - 2: refine intra mode search with SSE
      --(no-)mv-rdo          : Rate-Distortion Optimized motion vector costs
                             : Try all intra modes during rough search.
      --(no-)transform-skip  : Transform skip
      --me <string>          : Integer motion estimation
                                   - hexbs: Hexagon Based Search
                                   - tz:    Test Zone Search
                                   - full:  Full Search
                                   - full8, full16, full32, full64
      --subme <integer>      : Set fractional pixel motion estimation level
                                   - 0: only integer motion estimation
                                   - 1: + 1/2-pixel horizontal and vertical
                                   - 2: + 1/2-pixel diagonal
                                   - 3: + 1/4-pixel horizontal and vertical
                                   - 4: + 1/4-pixel diagonal
      --pu-depth-inter <int>-<int>
                             : Range for sizes for inter predictions
                                   - 0, 1, 2, 3: from 64x64 to 8x8
      --pu-depth-intra <int>-<int> : Range for sizes for intra predictions
                                   - 0, 1, 2, 3, 4: from 64x64 to 4x4
      --(no-)bipred          : Bi-prediction
                             : CU split search termination condition
                                   - off: Never terminate cu-split search
                                   - zero: Terminate with zero residual
      --(no-)me-early-termination : ME early termination condition
                                   - off: Don't terminate early
                                   - on: Terminate early
                                   - sensitive: Terminate even earlier
      --(no-)implicit-rdpcm  : Implicit residual DPCM
                               Currently only supported with lossless coding.
      --(no-)tmvp            : Temporal Motion Vector Prediction
      --(no-)rdoq-skip       : Skips RDOQ for 4x4 blocks

Parallel processing:
      --threads <integer>    : Number of threads to use [auto]
                                   - 0: process everything with main thread
                                   - N: use N threads for encoding
                                   - auto: select based on number of cores
      --owf <integer>        : Frame parallelism [auto]
                                   - N: Process N-1 frames at a time
                                   - auto: Select automatically
      --(no-)wpp             : Wavefront parallel processing [enabled]
                               Enabling tiles automatically disables WPP.
                               To enable WPP with tiles, re-enable it after
                               enabling tiles.
      --tiles <int>x<int>    : Split picture into width x height uniform tiles.
      --tiles-width-split <string>|u<int> :
                               Specifies a comma separated list of pixel
                               positions of tiles columns separation coordinates.
                               Can also be u followed by and a single int n,
                               in which case it produces columns of uniform width.
      --tiles-height-split <string>|u<int> :
                               Specifies a comma separated list of pixel
                               positions of tiles rows separation coordinates.
                               Can also be u followed by and a single int n,
                               in which case it produces rows of uniform height.
      --slices <string>      : Control how slices are used
                                   - tiles: put tiles in independent slices
                                   - wpp: put rows in dependent slices
                                   - tiles+wpp: do both

Video Usability Information:
      --sar <width:height>   : Specify Sample Aspect Ratio
      --overscan <string>    : Specify crop overscan setting [undef]
                                   - undef, show, crop
      --videoformat <string> : Specify video format [undef]
                                   - component, pal, ntsc, secam, mac, undef
      --range <string>       : Specify color range [tv]
                                   - tv, pc
      --colorprim <string>   : Specify color primaries [undef]
                                   - undef, bt709, bt470m, bt470bg,
                                     smpte170m, smpte240m, film, bt2020
      --transfer <string>    : Specify transfer characteristics [undef]
                                   - undef, bt709, bt470m, bt470bg,
                                     smpte170m, smpte240m, linear, log100,
                                     log316, iec61966-2-4, bt1361e,
                                     iec61966-2-1, bt2020-10, bt2020-12
      --colormatrix <string> : Specify color matrix setting [undef]
                                   - undef, bt709, fcc, bt470bg, smpte170m,
                                     smpte240m, GBR, YCgCo, bt2020nc, bt2020c
      --chromaloc <integer>  : Specify chroma sample location (0 to 5) [0]

Deprecated parameters: (might be removed at some point)
  -w, --width                 : Use --input-res
  -h, --height                : Use --input-res

LP-GOP syntax

The LP-GOP syntax is "lp-g(num)d(num)t(num)", where

  • g = GOP length.
  • d = Number of GOP layers.
  • t = How many references to skip for temporal scaling, where 4 means only
    every fourth picture needs to be decoded.
+4  o o o o  
+3   o   o    o o o o 
+2     o       o o o    ooooooo
+1 o       o o       o o       o ooooooooo
   g8d4t1    g8d3t1    g8d2t1    g8d1t1


The names of the presets are the same as with x264: ultrafast,
superfast, veryfast, faster, fast, medium, slow, slower, veryslow and
placebo. The effects of the presets are listed in the following table,
where the names have been abbreviated to fit the layout in GitHub.

0-uf 1-sf 2-vf 3-fr 4-f 5-m 6-s 7-sr 8-vs 9-p
rd 0 0 0 1 1 1 1 1 1 1
pu-depth-intra 2-3 2-3 2-3 2-3 2-3 1-3 1-3 1-3 1-4 1-4
pu-depth-inter 2-3 2-3 2-3 1-3 1-3 1-3 1-3 0-3 0-3 0-3
me hexbs hexbs hexbs hexbs hexbs hexbs hexbs hexbs hexbs tz
ref 1 1 1 1 1 1 2 2 3 4
deblock 1 1 1 1 1 1 1 1 1 1
signhide 0 0 0 0 0 0 1 1 1 1
subme 0 0 2 2 4 4 4 4 4 4
sao 0 1 1 1 1 1 1 1 1 1
rdoq 0 0 0 0 0 1 1 1 1 1
rdoq-skip 1 1 1 1 1 1 1 1 1 0
transform-skip 0 0 0 0 0 0 0 0 0 1
mv-rdo 0 0 0 0 0 0 0 0 0 1
full-intra-search 0 0 0 0 0 0 0 0 0 0
smp 0 0 0 0 0 0 0 0 0 1
amp 0 0 0 0 0 0 0 0 0 1
cu-split-termination zero zero zero zero zero zero zero zero zero off
me-early-termination sens. sens. sens. sens. on on on on on off

Kvazaar library

See kvazaar.h for the library API and its

When using the static Kvazaar library on Windows, macro KVZ_STATIC_LIB
must be defined. On other platforms it's not strictly required.

The needed linker and compiler flags can be obtained with pkg-config.

Compiling Kvazaar

If you have trouble regarding compiling the source code, please make an
issue about in Github.
Others might encounter the same problem and there is probably much to
improve in the build process. We want to make this as simple as

Required libraries

  • For Visual Studio, the pthreads-w32 library is required. Platforms
    with native POSIX thread support don't need anything.
    • The project file expects the library to be in ../pthreads.2/
      relative to Kvazaar. You can just extract the pre-built library
    • The executable needs pthreadVC2.dll to be present. Either install it
      somewhere or ship it with the executable.


Depending on the platform, some additional tools are required for compiling Kvazaar with autotools.
For Ubuntu, the required packages are automake autoconf libtool m4 build-essential yasm. Yasm is
optional, but some of the optimization will not be compiled in if it's missing.

Run the following commands to compile and install Kvazaar.

sudo make install

See ./configure --help for more options.


  • Install Homebrew
  • run brew install automake libtool yasm
  • Refer to Autotools instructions

Visual Studio

  • At least VisualStudio 2013 is required.
  • Project files can be found under build/.
  • Requires external vsyasm.exe
    in %PATH%


This project includes a Dockerfile, which enables building for Docker. Kvazaar is also available in the Docker Hub ultravideo/kvazaar
Build using Docker: docker build -t kvazaar .
Example usage: docker run -i -a STDIN -a STDOUT kvazaar -i - --input-res=320x240 -o - < testfile_320x240.yuv > out.265
For other examples, see Dockerfile

Visualization (Windows only)

Branch visualizer has a visual studio project, which can be compiled to enable visualization feature in Kvazaar.

Additional Requirements: SDL2, SDL2-ttf.

Directory visualizer_extras is expected to be found from the same directory level as the kvazaar project directory. Inside should be directories include and lib found from the development library zip packages.

SDL2.dll, SDL2_ttf.dll, libfreetype-6.dll, zlib1.dll, and pthreadVC2.dll should be placed in the working directory (i.e. the folder the kvazaar.exe is in after compiling the kvazaar_cli project/solution) when running the visualizer. The required .dll can be found in the aforementioned lib-folder (lib\x64) and the dll folder inside the pthreads folder (see Required libraries).

Note: The solution should be compiled on the x64 platform in visual studio.

Optional font file arial.ttf is to be placed in the working directory, if block info tool is used.

Contributing to Kvazaar

We are happy to look at pull requests in Github. There is still lots of work to be done.

Code documentation

You can generate Doxygen documentation pages by running the command
"doxygen docs.doxy". Here is a rough sketch of the module structure:

For version control we try to follow these conventions:

  • Master branch always produces a working bitstream (can be decoded with
  • Commits for new features and major changes/fixes put to a sensibly
    named feature branch first and later merged to the master branch.
  • Always merge the feature branch to the master branch, not the other
    way around, with fast-forwarding disabled if necessary.
  • Every commit should at least compile.


  • Main automatic way of testing is with Travis CI. Commits, branches
    and pull requests are tested automatically.
    • Uninitialized variables and such are checked with Valgrind.
    • Bitstream validity is checked with HM.
    • Compilation is checked on GCC and Clang on Linux, and Clang on OSX.
  • Windows msys2 build is checked automatically on Appveyor.
  • If your changes change the bitstream, decode with HM to check that
    it doesn't throw checksum errors or asserts.
  • If your changes shouldn't alter the bitstream, check that they don't.
  • Automatic compression quality testing is in the works.

Unit tests

  • There are some unit tests located in the tests directory. We would
    like to have more.
  • The Visual Studio project links the unit tests against the actual .lib
    file used by the encoder. There is no Makefile as of yet.
  • The unit tests use "greatest" unit testing framework. It is included
    as a submodule, but getting it requires the following commands to be
    run in the root directory of kvazaar:

      git submodule init
      git submodule update
  • On Linux, run make test.

Code style

We try to follow the following conventions:

  • C99 without features not supported by Visual Studio 2013 (VLAs).
    • // comments allowed and encouraged.
  • Follow overall conventions already established in the code.
  • Indent by 2 spaces. (no tabs)
  • { on the same line for control logic and on the next line for functions
  • Reference and deference next to the variable name.
  • Variable names in lowered characters with words divided by underscore.
  • Maximum line length 79 characters when possible.
  • Functions only used inside the module shouldn't be defined in the
    module header. They can be defined in the beginning of the .c file if
  • Symbols defined in headers prefixed with kvz or KVZ.
  • Includes in alphabetic order.
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