VStabiliser interface C++ library

v2.4.4

Table of contents

• Overview
• Versions
• Library files
• VStabiliser class description
  • VStabiliser class declaration
  • getVersion method
  • initVStabiliser method
  • setParam method
  • getParam method
  • getParams method
  • executeCommand method
  • stabilise method
  • getOffsets methods
  • encodeSetParamCommand method
  • encodeCommand method
  • decodeCommand method
  • decodeAndExecuteCommand method
• Data structures
  • VStabiliserParam enum
  • VStabiliserCommand enum
• VStabiliserParams class description
  • VStabiliserParams class declaration
  • Serialize video stabiliser params
  • Deserialize video stabiliser params
  • Read params from JSON file and write to JSON file
• Build and connect to your project
• How to make custom implementation

Overview

VStabiliser C++ library provides standard interface as well defines data structures and rules for different implementation of video stabilization algorithms. VStabiliser interface class doesn't do anything, just provides interface, defines data structures and provides methods to encode/decode commands and encode/decode params. Different video stabilizer classes inherit interface form VStabiliser C++ class. VStabiliser.h file contains list of data structures (VStabiliserCommand enum, VStabiliserParam enum and VStabiliserParams class) and VStabiliser class declaration. VStabiliserCommand enum contains IDs of commands supported by VStabiliser class. VStabiliserParam enum contains IDs of params supported by VStabiliser class. VStabiliserParams class contains fields for video stabilizer params values and provides methods to encode/decode and read/write params from JSON file. All video stabilizers should include params and commands listed in VStabiliser.h file. VStabiliser class depends on two external libraries (included as submodule): Frame (describes video frame data structure, source code included, Apache 2.0 license) and ConfigReader (provides methods to read/write JSON config files, source code included, Apache 2.0 license). It uses C++17 standard. The library is licensed under the Apache 2.0 license.

Versions

Table 1 - Library versions.

Version	Release date	What's new
1.0.0	18.05.2023	First version.
2.0.0	11.07.2023	- Added VStabiliserParams class to keep library parameters. - Added method to encode/decode commands. - Added test application. - Added license. - Repository made public.
2.0.1	12.07.2023	- Fixed typo in VStabiliserParams - Updated test application.
2.1.0	30.07.2023	- Switched from radians to radians in params.
2.2.0	24.07.2023	- Updated encode(...) and decode(...) methods of VStabiliserParams. - Added decodeAndExecuteCommand(...) method. - Added example of video stabiliser implementation.
2.3.0	26.09.2023	- Signature of getParams(...) method changed.
2.3.1	13.11.2023	- Frame class updated.
2.4.1	14.12.2023	- Virtual destructor added. - Frame class updated.
2.4.2	04.01.2024	- GitHub compliant license added.
2.4.3	25.03.2024	- Frame class updated. - ConfigReader class updated. - Documentation updated.

Library files

The library supplied by source code only. The user would be given a set of files in the form of a CMake project (repository). The repository structure is shown below:

CMakeLists.txt ------------------- Main CMake file of the library.
3rdparty ------------------------- Folder with third-party libraries.
    CMakeLists.txt --------------- CMake file which includes third-party. libraries.
    ConfigReader ----------------- Folder with ConfigReader library source code.
    Frame ------------------------ Folder with Frame library source code.
example -------------------------- Folder with custom video stabilizer class.
    CMakeLists.txt --------------- CMake file for custom video stabilizer class.
    CustomVStabiliser.cpp -------- Source code file of the CustomVStabiliser class.
    CustomVStabiliser.h ---------- Header with CustomVStabiliser class declaration.
    CustomVStabiliserVersion.h --- Header file which includes CustomVStabiliser version.
    CustomVStabiliserVersion.h.in  CMake service file to generate version file.
test ----------------------------- Folder with test application.
    CMakeLists.txt --------------- CMake file for test application.
    main.cpp --------------------- Source code file of test application.
src ------------------------------ Folder with source code of the library.
    CMakeLists.txt --------------- CMake file of the library.
    VStabiliser.cpp -------------- Source code file of the library.
    VStabiliser.h ---------------- Header file which includes VStabiliser class declaration.
    VStabiliserVersion.h --------- Header file which includes version of the library.
    VStabiliserVersion.h.in ------ CMake service file to generate version file.

VStabiliser class description

VStabiliser class declaration

VStabiliser.h file contains VStabiliser class declaration. Class declaration:

class VStabiliser
{
public:

    /// Class destructor.
    virtual ~VStabiliser();
    
    /// Get string of current class version.
    static std::string getVersion();

    /// Init all video stabiliser params by params structure.
    virtual bool initVStabiliser(VStabiliserParams& params) = 0;

    /// Set param.
    virtual bool setParam(VStabiliserParam id, float value) = 0;

    /// Get param.
    virtual float getParam(VStabiliserParam id) = 0;

    /// Get params.
    virtual void getParams(VStabiliserParams& params) = 0;

    /// Execute command.
    virtual bool executeCommand(VStabiliserCommand id) = 0;

    /// Stabilise video frame.
    virtual bool stabilise(cr::video::Frame& src, cr::video::Frame& dst) = 0;

    /// Get offsets: horithontal, vertical and rotation.
    virtual void getOffsets(float& dX, float& dY, float& dA) = 0;

    /// Encode set param command.
    static void encodeSetParamCommand(
            uint8_t* data, int& size, VStabiliserParam id, float value);

    /// Encode command.
    static void encodeCommand(
            uint8_t* data, int& size, VStabiliserCommand id);

    /// Decode command.
    static int decodeCommand(uint8_t* data,
                             int size,
                             VStabiliserParam& paramId,
                             VStabiliserCommand& commandId,
                             float& value);

    /// Decode and execute command.
    virtual bool decodeAndExecuteCommand(uint8_t* data, int size) = 0;
};

getVersion method

The getVersion() method return string of current version of VStabiliser class. Method declaration:

static std::string getVersion();

Method can be used without VStabiliser class instance. Example:

cout << "VStabiliser class version: " << VStabiliser::getVersion() << endl;

Console output:

VStabiliser class version: 2.4.4

initVStabiliser method

The initVStabiliser(...) method initializes video stabilizer parameters by parameters structure. Method copy all video stabilizer parameter to internal variables. Method declaration:

virtual bool initVStabiliser(VStabiliserParams& params) = 0;

Parameter	Description
params	Parameters class (see VStabiliserParams class description).

Returns: TRUE if params was accepted or FALSE if not.

setParam method

The setParam(...) method intended to change video stabilizer parameter. The particular implementation of the video stabilizer must provide thread-safe setParam(...) method call. This means that the setParam(...) method can be safely called from any thread. Method declaration:

virtual bool setParam(cr::vstab::VStabiliserParam id, float value) = 0;

Parameter	Description
id	Parameter ID according to VStabiliserParam enum.
value	Parameter value. Depends on parameter ID.

Returns: TRUE if param was accepted or FALSE if not.

getParam method

The getParam(...) method intended to get video stabilizer parameter value. The particular implementation of the video stabilizer must provide thread-safe getParam(...) method call. This means that the getParam(...) method can be safely called from any thread. Method declaration:

virtual float getParam(cr::vstab::VStabiliserParam id) = 0;

Parameter	Description
id	Parameter ID according to VStabiliserParam enum.

Returns: Parameter value or -1 if this param not supported by implementation.

getParams method

The getParams(...) method designed to obtain all video stabilizer parameters. The particular implementation of the video stabilizer must provide thread-safe getParams(...) method call. This means that the getParams(...) method can be safely called from any thread. Method declaration:

virtual void getParams(VStabiliserParams& params) = 0;

Parameter	Description
params	VStabiliserParams class object.

executeCommand method

The executeCommand(...) method intended to execute video stabilizer command. The particular implementation of the video stabiliser must provide thread-safe executeCommand(...) method call. This means that the executeCommand(...) method can be safely called from any thread. Method declaration:

virtual bool executeCommand(cr::vstab::VStabiliserCommand id) = 0;

Parameter	Description
id	Command ID according to VStabiliserCommand enum.

Returns: TRUE if the command executed or FALSE if not.

stabilise method

The stabilise(...) method performs video stabilization. Method declaration:

virtual bool stabilise(cr::video::Frame& src, cr::video::Frame& dst) = 0;

Parameter	Description
src	Source frame. The methods accepts only RAW frame data (not compressed pixel formats, see description of Frame class). Particular implementation can support all, only one or few pixel formats listed in Frame class description.
dst	Result frame. The pixel format of the result frame must be the same as source frame. If stabilization disabled (param MODE set to 0) the library must copy data from source frame to result frame.

Returns: TRUE if video frame processed or FALSE in case any errors.

getOffsets methods

The getOffsets(...) method returns horizontal offset (pixels), vertical offset (pixels) and rotation angle (radians) implemented to last processed video frame (stabilise method). The particular implementation of the video stabiliser must provide thread-safe getOffsets(...) method call. This means that the getOffsets(...) method can be safely called from any thread. Method declaration:

virtual void getOffsets(float& dX, float& dY, float& dA) = 0;

Parameter	Description
dX	Reference to output value of horizontal offset (pixels) implemented to last processed video frame.
dY	Reference to output value of vertical offset (pixels) implemented to last processed video frame.
dA	Reference to output value of rotational angle (radians) implemented to last processed video frame.

encodeSetParamCommand method

The encodeSetParamCommand(...) static method designed to encode command to change any parameters of remote video stabiliser. To control a stabiliser remotely, the developer has to develop his own protocol and according to it encode the command and deliver it over the communication channel. To simplify this, the VStabiliser class contains static methods for encoding the control commands. The VStabiliser class provides two types of commands: a parameter change command (SET_PARAM) and an action command (COMMAND). encodeSetParamCommand(...) designed to encode SET_PARAM command. Method declaration:

static void encodeSetParamCommand(uint8_t* data, int& size, VStabiliserParam id, float value);

Parameter	Description
data	Pointer to data buffer for encoded command. Must have size >= 11.
size	Size of encoded data. Will be 11 bytes.
id	Parameter ID according to VStabiliserParam enum.
value	Parameter value.

encodeSetParamCommand(...) is static and used without VStabiliser class instance. This method used on client side (control system). Example:

// Buffer for encoded data.
uint8_t data[11];
// Size of encoded data.
int size = 0;
// Random parameter value.
float outValue = (float)(rand() % 20);
// Encode command.
VStabiliser::encodeSetParamCommand(data, size, VStabiliserParam::INSTANT_X_OFFSET, outValue);

encodeCommand method

The encodeCommand(...) static method designed to encode video stabiliser action command. To control a stabiliser remotely, the developer has to develop his own protocol and according to it encode the command and deliver it over the communication channel. To simplify this, the VStabiliser class contains static methods for encoding the control commands. The VStabiliser class provides two types of commands: a parameter change command (SET_PARAM) and an action command (COMMAND). encodeCommand(...) designed to encode COMMAND command (action command). Method declaration:

static void encodeCommand(uint8_t* data, int& size, VStabiliserCommand id);

Parameter	Description
data	Pointer to data buffer for encoded command. Must have size >= 11.
size	Size of encoded data. Will be 7 bytes.
id	Command ID according to VStabiliserCommand enum.

encodeCommand(...) is static and used without VStabiliser class instance. This method used on client side (control system). Encoding example:

// Buffer for encoded data.
uint8_t data[11];
// Size of encoded data.
int size = 0;
// Encode command.
VStabiliser::encodeCommand(data, size, VStabiliserCommand::ON);

decodeCommand method

The decodeCommand(...) static method designed to decode command on video stabiliser side. To control a stabiliser remotely, the developer has to develop his own protocol and according to it encode the command and deliver it over the communication channel. To simplify this, the VStabiliser interface class contains static method to decode input command (commands should be encoded by methods encodeSetParamsCommand(...) or encodeCommand(...)). The VStabiliser class provides two types of commands: a parameter change command (SET_PARAM) and an action command (COMMAND). Method declaration:

static int decodeCommand(uint8_t* data, int size, VStabiliserParam& paramId, VStabiliserCommand& commandId, float& value);

Parameter	Description
data	Pointer to input command.
size	Size of command. Should be 11 bytes (for SET_PARAMS) or 7 bytes for (COMMAND).
paramId	Video stabiliser parameter ID according to VStabiliserParam enum. After decoding SET_PARAM command the method will return parameter ID.
commandId	Video stabiliser command ID according toVStabiliserCommand enum. After decoding COMMAND the method will return command ID.
value	Video stabiliser parameter value after decoding SET_PARAM command.

Returns: 0 - in case decoding COMMAND, 1 - in case decoding SET_PARAM command or -1 in case errors.

decodeCommand(...) is static and used without VStabiliser class instance. Command decoding example:

// Buffer for encoded data.
uint8_t data[11];
int size = 0;
VStabiliser::encodeCommand(data, size, VStabiliserCommand::ON);

// Decode command.
VStabiliserCommand commandId;
VStabiliserParam paramId;
float value = (float)(rand() % 20);
if (VStabiliser::decodeCommand(data, size, paramId, commandId, value) != 0)
{
    cout << "Command not decoded" << endl;
    return false;
}

decodeAndExecuteCommand method

The decodeAndExecuteCommand(...) method decodes and executes command on video stabiliser side. The particular implementation of the video stabiliser must provide thread-safe decodeAndExecuteCommand(...) method call. This means that the decodeAndExecuteCommand(...) method can be safely called from any thread. Method declaration:

virtual bool decodeAndExecuteCommand(uint8_t* data, int size) = 0;

Parameter	Description
data	Pointer to input command.
size	Size of command. Must be 11 bytes for SET_PARAM or 7 bytes for COMMAND.

Returns: TRUE if command decoded (SET_PARAM or COMMAND) and executed (action command or set param command).

Data structures

VStabiliserParam enum

VStabiliserParam enum lists video stabiliser parameters to set or to obtain. Enum declaration.

enum class VStabiliserParam
{
    /// Scale factor. Value depends on implementation. Default:
    /// If 1 the library will process original frame size, if 2
    /// the library will scale original frame size by 2, if 3 - by 3.
    SCALE_FACTOR = 1,
    /// Maximum horizontal image shift in pixels per video frame. If image shift
    /// bigger than this limit the library should compensate only X_OFFSET_LIMIT
    /// shift.
    X_OFFSET_LIMIT,
    /// Maximum vertical image shift in pixels per video frame. If image shift
    /// bigger than this limit the library should compensate only Y_OFFSET_LIMIT
    /// shift.
    Y_OFFSET_LIMIT,
    /// Maximum rotational image angle in radians per video frame. If image
    /// absolute rotational angle bigger than this limit the library should
    /// compensate only A_OFFSET_LIMIT angle.
    A_OFFSET_LIMIT,
    /// Horizontal smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilization
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    X_FILTER_COEFF,
    /// Vertical smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilization
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    Y_FILTER_COEFF,
    /// Rotational smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilization
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    A_FILTER_COEFF,
    /// Stabilization mode:
    /// 0 - Stabilization off. The library should just copy input image.
    /// 1 - Stabilization on.
    MODE,
    /// Transparent border mode:
    /// 0 - Not transparent borders (black borders).
    /// 1 - Transparent borders (parts of previous images).
    /// Particular implementation can have additional modes.
    TRANSPARENT_BORDER,
    /// Constant horizontal image offset in pixels. The library should add this
    /// offset to each processed video frame.
    CONST_X_OFFSET,
    /// Constant vertical image offset in pixels. The library should add this
    /// offset to each processed video frame.
    CONST_Y_OFFSET,
    /// Constant rotational angle in radians. The library should add this
    /// offset to each processed video frame.
    CONST_A_OFFSET,
    /// Instant (for one frame) horizontal image offset in pixels. The library
    /// should add this offset to next processed video frame.
    INSTANT_X_OFFSET,
    /// Instant (for one frame) vertical image offset in pixels. The library
    /// should add this offset to next processed video frame.
    INSTANT_Y_OFFSET,
    /// Instant (for one frame) rotational angle in radians. The library
    /// should add this offset to next processed video frame.
    INSTANT_A_OFFSET,
    /// Algorithm type. Default values:
    /// 0 - 2D type 1. Stabilization only on horizontal and vertical.
    /// 1 - 2D type 2. Stabilization only on horizontal and vertical.
    /// 2 - 3D. Stabilization on horizontal and vertical + rotation.
    /// Particular implementation can have unique values.
    TYPE,
    /// Cat frequency, Hz. Stabiliser will block vibrations with frequency
    /// > CUT_FREQUENCY_HZ.
    CUT_FREQUENCY_HZ,
    /// Frames per second of input video.
    FPS,
    /// Processing time, mks. Processing time for last video frame.
    PROCESSING_TIME_MKS,
    /// Logging mode. Values: 0 - Disable, 1 - Only file, 2 - Only terminal,
    /// 3 - File and terminal.
    LOG_MODE
};

Table 2 - Video stabiliser parameters description.

Parameter	Description
SCALE_FACTOR	Scale factor. Value depends on implementation. Default: If 1 the library will process original frame size, if 2 the library will scale original frame size by 2, if 3 - by 3.
X_OFFSET_LIMIT	Maximum horizontal image shift in pixels per video frame. If image shift bigger than this limit the library should compensate only X_OFFSET_LIMIT shift.
Y_OFFSET_LIMIT	Maximum vertical image shift in pixels per video frame. If image shift bigger than this limit the library should compensate only Y_OFFSET_LIMIT shift.
A_OFFSET_LIMIT	Maximum rotational image angle in radians per video frame. If image absolute rotational angle bigger than this limit the library should compensate only A_OFFSET_LIMIT angle.
X_FILTER_COEFF	Horizontal smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilization algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
Y_FILTER_COEFF	Vertical smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilization algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
A_FILTER_COEFF	Rotational smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilization algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
MODE	Stabilization mode: 0 - Stabilization off. The library should just copy input image. 1 - Stabilization on.
TRANSPARENT_BORDER	Transparent border mode: 0 - Not transparent borders (black borders). 1 - Transparent borders (parts of previous images). Particular implementation can have additional modes.
CONST_X_OFFSET	Constant horizontal image offset in pixels. The library should add this offset to each processed video frame.
CONST_Y_OFFSET	Constant vertical image offset in pixels. The library should add this offset to each processed video frame.
CONST_A_OFFSET	Constant rotational angle in radians. The library should add this offset to each processed video frame.
INSTANT_X_OFFSET	Instant (for one frame) horizontal image offset in pixels. The library should add this offset to next processed video frame.
INSTANT_Y_OFFSET	Instant (for one frame) vertical image offset in pixels. The library should add this offset to next processed video frame.
INSTANT_A_OFFSET	Instant (for one frame) rotational angle in radians. The library should add this offset to next processed video frame.
TYPE	Algorithm type. Particular implementation can have unique values. Default values: 0 - 2D. Stabilization only on horizontal and vertical directions. 1 - 3D. Stabilization on horizontal and vertical directions + rotation.
CUT_FREQUENCY_HZ	Cat frequency, Hz. Stabiliser will block vibrations with frequency CUT_FREQUENCY_HZ.
FPS	Frames per second of input video.
PROCESSING_TIME_MKS (Read only parameter)	Processing time, mks. Processing time for last video frame.
LOG_MODE	Logging mode. Values: 0 - Disable, 1 - Only file, 2 - Only terminal, 3 - File and terminal.

VStabiliserCommand enum

VStabiliserCommand enum lists video stabiliser commands. Enum declaration.

enum class VStabiliserCommand
{
    /// Reset stabilisation algorithm.
    RESET = 1,
    /// Enable stabilisation. After execution parameter MODE must be set to 1.
    ON,
    /// Disable stabilisation. After execution parameter MODE must be set to 0.
    OFF
};

Table 3 - Video stabiliser commands description.

Parameter	Description
RESET	Reset stabilisation algorithm.
ON	Enable stabilisation. After execution parameter MODE must be set to 1.
OFF	Disable stabilisation. After execution parameter MODE must be set to 0.

VStabiliserParams class description

VStabiliserParams class used for video stabiliser initialization (initVStabiliser(...) method) or to get all actual params (getParams() method). Also VStabiliserParams provide structure to write/read params from JSON files (JSON_READABLE macro) and provide methos to encode and decode params.

VStabiliserParams class declaration

VStabiliser.h file contains VStabiliserParams class declaration. Class declaration:

class VStabiliserParams
{
public:
    /// Scale factor. Value depends on implementation. Default:
    /// If 1 the library will process original frame size, if 2
    /// the library will scale original frame size by 2, if 3 - by 3.
    int scaleFactor{1};
    /// Maximum horizontal image shift in pixels per video frame. If image shift
    /// bigger than this limit the library should compensate only xOffsetLimit
    /// shift.
    int xOffsetLimit{150};
    /// Maximum vertical image shift in pixels per video frame. If image shift
    /// bigger than this limit the library should compensate only yOffsetLimit
    /// shift.
    int yOffsetLimit{150};
    /// Maximum rotational image angle in readians per video frame. If image
    /// absolute rotational angle bigger than this limit the library should
    /// compensate only aOffsetLimit angle.
    float aOffsetLimit{10.0f};
    /// Horizontal smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilisation
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    float xFilterCoeff{0.9f};
    /// Vertical smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilisation
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    float yFilterCoeff{0.9f};
    /// Rotational smoothing coefficient of constant camera movement. The range
    /// of values depends on the specific implementation of the stabilisation
    /// algorithm. Default values [0-1]: 0 - the library will not compensate for
    /// constant camera motion, video will not be stabilized, 1 - no smoothing
    /// of constant camera motion (the library will compensate for the current
    /// picture drift completely without considering constant motion).
    float aFilterCoeff{0.9f};
    /// Enable/disable stabilisation.
    bool enable{true};
    /// Enable/disable trasparent borders.
    bool transparentBorder{true};
    /// Constant horizontal image offset in pixels. The library should add this
    /// offset to each processed video frame.
    int constXOffset{0};
    /// Constant vertical image offset in pixels. The library should add this
    /// offset to each processed video frame.
    int constYOffset{0};
    /// Constant rotational angle in radians. The library should add this
    /// offset to each processed video frame.
    float constAOffset{0.0f};
    /// Instant (for one frame) horizontal image offset in pixels. The library
    /// should add this offset to next processed video frame.
    int instantXOffset{0};
    /// Instant (for one frame) vertical image offset in pixels. The library
    /// should add this offset to next processed video frame.
    int instantYOffset{0};
    /// Instant (for one frame) rotational angle in radians. The library
    /// should add this offset to next processed video frame.
    float instantAOffset{0.0f};
    /// Algorithm type. Default values:
    /// 0 - 2D type 1. Stabilisation only on horizontal and vertical.
    /// 1 - 2D type 2. Stabilisation only on horizontal and vertical.
    /// 2 - 3D. Stabilisation on horizontal and vertical + rotation.
    /// Particular implementation can have unique values.
    int type{2};
    /// Cat frequency, Hz. Stabiliser will block vibrations with frequency
    /// > cutFrequencyHz.
    float cutFrequencyHz{2.0f};
    /// Frames per second of input video.
    float fps{30.0f};
    /// Processing time, mks. Processing time for last video frame.
    int processingTimeMks{0};
    /// Logging mode. Values: 0 - Disable, 1 - Only file, 2 - Only terminal,
    /// 3 - File and terminal.
    int logMod{0};

    JSON_READABLE(VStabiliserParams, scaleFactor, xOffsetLimit, yOffsetLimit,
                  aOffsetLimit, xFilterCoeff, yFilterCoeff, aFilterCoeff,
                  enable, transparentBorder, constXOffset, constYOffset,
                  constAOffset, type, cutFrequencyHz, fps, logMod);

    /// operator =
    VStabiliserParams& operator= (const VStabiliserParams& src);

    /// Encode params.
    bool encode(uint8_t* data, int bufferSize,
                int& size, VStabiliserParamsMask* mask = nullptr);

    /// Decode params.
    bool decode(uint8_t* data, int dataSize);
};

Table 4 - VStabiliserParams class fields description is equivalent to VStabiliserParam enum description.

Field	type	Description
scaleFactor	int	Scale factor. Value depends on implementation. Default: If 1 the library will process original frame size, if 2 the library will scale original frame size by 2, if 3 - by 3.
xOffsetLimit	int	Maximum horizontal image shift in pixels per video frame. If image shift bigger than this limit the library should compensate only xOffsetLimit shift.
yOffsetLimit	int	Maximum vertical image shift in pixels per video frame. If image shift bigger than this limit the library should compensate only yOffsetLimit shift.
aOffsetLimit	float	Maximum rotational image angle in radians per video frame. If image absolute rotational angle bigger than this limit the library should compensate only aOffsetLimit angle.
xFilterCoeff	float	Horizontal smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilisation algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
yFilterCoeff	float	Vertical smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilisation algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
aFilterCoeff	float	Rotational smoothing coefficient of constant camera movement. The range of values depends on the specific implementation of the stabilisation algorithm. Default values [0-1]: 0 - the library will not compensate for constant camera motion, video will not be stabilized, 1 - no smoothing of constant camera motion (the library will compensate for the current picture drift completely without considering constant motion).
enable	bool	Enable/disable stabilisation.
transparentBorder	bool	Enable/disable transparent borders.
constXOffset	int	Constant horizontal image offset in pixels. The library should add this offset to each processed video frame.
constYOffset	int	Constant vertical image offset in pixels. The library should add this offset to each processed video frame.
constAOffset	float	Constant rotational angle in radians. The library should add this offset to each processed video frame.
instantXOffset	int	Instant (for one frame) horizontal image offset in pixels. The library should add this offset to next processed video frame.
instantYOffset	int	Instant (for one frame) vertical image offset in pixels. The library should add this offset to next processed video frame.
instantAOffset	int	Instant (for one frame) rotational angle in radians. The library should add this offset to next processed video frame.
type	int	Algorithm type. Default values: 0 - 2D type 1. Stabilization only on horizontal and vertical. 1 - 2D type 2. Stabilization only on horizontal and vertical. 2 - 3D. Stabilization on horizontal and vertical + rotation. Particular implementation can have unique values.
cutFrequencyHz	float	Cat frequency, Hz. Stabiliser will block vibrations with frequency > cutFrequencyHz.
fps	float	Frames per second of input video.
processingTimeMks (read only parameter)	int	Processing time, mks. Processing time for last video frame.
logMod	int	Logging mode. Values: 0 - Disable, 1 - Only file, 2 - Only terminal, 3 - File and terminal.

None: VStabiliserParams class fields listed in Table 4 must reflect params set/get by methods setParam(...) and getParam(...).

Serialize video stabiliser params

VStabiliserParams class provides method encode(...) to serialize video stabiliser params (fields of VStabiliserParams class, see Table 4). Serialization of params necessary in case when you need to send params via communication channels. Method provide options to exclude particular parameters from serialization. To do this method inserts binary mask (3 bytes) where each bit represents particular parameter and decode(...) method recognizes it. Method declaration:

bool encode(uint8_t* data, int bufferSize, int& size, VStabiliserParamsMask* mask = nullptr);

Parameter	Value
data	Pointer to data buffer.
bufferSize	Data buffer size. Must have size >= 80 bytes.
size	Size of encoded data.
mask	Parameters mask - pointer to VStabiliserParamsMask structure. VStabiliserParamsMask (declared in VStabiliser.h file) determines flags for each field (parameter) declared in VStabiliserParams class. If the user wants to exclude any parameters from serialization, he can put a pointer to the mask. If the user wants to exclude a particular parameter from serialization, he should set the corresponding flag in the VStabiliserParamsMask structure.

VStabiliserParamsMask structure declaration:

typedef struct VStabiliserParamsMask
{
    bool scaleFactor{true};
    bool xOffsetLimit{true};
    bool yOffsetLimit{true};
    bool aOffsetLimit{true};
    bool xFilterCoeff{true};
    bool yFilterCoeff{true};
    bool aFilterCoeff{true};
    bool enable{true};
    bool transparentBorder{true};
    bool constXOffset{true};
    bool constYOffset{true};
    bool constAOffset{true};
    bool instantXOffset{false};
    bool instantYOffset{false};
    bool instantAOffset{false};
    bool type{true};
    bool cutFrequencyHz{true};
    bool fps{true};
    bool processingTimeMks{true};
    bool logMod{true};
} VStabiliserParamsMask;

Example without parameters mask:

// Encode data.
VStabiliserParams in;
uint8_t data[1024];
int size = 0;
in.encode(data, 1024, size);
cout << "Encoded data size: " << size << " bytes" << endl;

Example without parameters mask:

// Prepare mask.
VStabiliserParamsMask mask;
mask.scaleFactor = true; // Exclude scaleFactor. Others by default.

// Encode data.
VStabiliserParams in;
uint8_t data[1024];
int size = 0;
in.encode(data, 1024, size, &mask);
cout << "Encoded data size: " << size << " bytes" << endl;

Deserialize video stabiliser params

VStabiliserParams class provides method decode(...) to deserialize params (fields of VStabiliserParams class, see Table 4). Deserialization of params necessary in case when you need to receive params via communication channels. Method automatically recognizes which parameters were serialized by encode(...) method. Method declaration:

bool decode(uint8_t* data, int dataSize);

Parameter	Value
data	Pointer to data buffer.

Returns: TRUE if data decoded (deserialized) or FALSE if not.

Example:

// Encode data.
VStabiliserParams in;
uint8_t data[1024];
int size = 0;
in.encode(data, 1024, size);
cout << "Encoded data size: " << size << " bytes" << endl;

// Decode data.
VStabiliserParams out;
if (!out.decode(data))
    cout << "Can't decode data" << endl;

Read params from JSON file and write to JSON file

VStabiliser interface class library depends on ConfigReader library which provides method to read params from JSON file and to write params to JSON file. Example of writing and reading params to JSON file:

// Prepare random params.
VStabiliserParams in;
in.scaleFactor = rand() % 255;
in.xOffsetLimit = rand() % 255;
in.yOffsetLimit = rand() % 255;
in.aOffsetLimit = static_cast<float>(rand() % 255);

// Write params to file.
cr::utils::ConfigReader inConfig;
inConfig.set(in, "VStabiliserParams");
inConfig.writeToFile("TestVStabiliserParams.json");

// Read params from file.
cr::utils::ConfigReader outConfig;
if(!outConfig.readFromFile("TestVStabiliserParams.json"))
{
    cout << "Can't open config file" << endl;
    return false;
}

VStabiliserParams out;
if(!outConfig.get(out, "VStabiliserParams"))
{
    cout << "Can't read params from file" << endl;
    return false;
}

TestVStabiliserParams.json will look like:

{
    "VStabiliserParams": {
        "aFilterCoeff": 5.0,
        "aOffsetLimit": 13.0,
        "constAOffset": 16.0,
        "constXOffset": 57,
        "constYOffset": 33,
        "cutFrequencyHz": 161.0,
        "enable": false,
        "fps": 90.0,
        "logMod": 99,
        "scaleFactor": 53,
        "transparentBorder": true,
        "type": 208,
        "xFilterCoeff": 76.0,
        "xOffsetLimit": 51,
        "yFilterCoeff": 230.0,
        "yOffsetLimit": 244
    }
}

Build and connect to your project

Typical commands to build VStabiliser library:

git clone https://github.com/ConstantRobotics-Ltd/VStabiliser.git
cd VStabiliser
git submodule update --init --recursive
mkdir build
cd build
cmake ..
make

If you want connect VStabiliser library to your CMake project as source code you can make follow. For example, if your repository has structure:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp

You can add repository VStabiliser as submodule by commands:

cd <your respository folder>
git submodule add https://github.com/ConstantRobotics-Ltd/VStabiliser.git 3rdparty/VStabiliser
git submodule update --init --recursive

In you repository folder will be created folder 3rdparty/VStabiliser which contains files of VStabiliser repository with subrepositories Frame and ConfigReader. New structure of your repository:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp
3rdparty
    VStabiliser

Create CMakeLists.txt file in 3rdparty folder. CMakeLists.txt should contain:

cmake_minimum_required(VERSION 3.13)

################################################################################
## 3RD-PARTY
## dependencies for the project
################################################################################
project(3rdparty LANGUAGES CXX)

################################################################################
## SETTINGS
## basic 3rd-party settings before use
################################################################################
# To inherit the top-level architecture when the project is used as a submodule.
SET(PARENT ${PARENT}_YOUR_PROJECT_3RDPARTY)
# Disable self-overwriting of parameters inside included subdirectories.
SET(${PARENT}_SUBMODULE_CACHE_OVERWRITE OFF CACHE BOOL "" FORCE)

################################################################################
## CONFIGURATION
## 3rd-party submodules configuration
################################################################################
SET(${PARENT}_SUBMODULE_VSTABILISER                     ON  CACHE BOOL "" FORCE)
if (${PARENT}_SUBMODULE_VSTABILISER)
    SET(${PARENT}_VSTABILISER                           ON  CACHE BOOL "" FORCE)
    SET(${PARENT}_VSTABILISER_TEST                      OFF CACHE BOOL "" FORCE)
    SET(${PARENT}_VSTABILISER_EXAMPLE                   OFF CACHE BOOL "" FORCE)
endif()

################################################################################
## INCLUDING SUBDIRECTORIES
## Adding subdirectories according to the 3rd-party configuration
################################################################################
if (${PARENT}_SUBMODULE_VSTABILISER)
    add_subdirectory(VStabiliser)
endif()

File 3rdparty/CMakeLists.txt adds folder VStabiliser to your project and excludes test application (VStabiliser class test applications) from compiling. Your repository new structure will be:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp
3rdparty
    CMakeLists.txt
    VStabiliser

Next you need include folder 3rdparty in main CMakeLists.txt file of your repository. Add string at the end of your main CMakeLists.txt:

add_subdirectory(3rdparty)

Next you have to include VStabiliser library in your src/CMakeLists.txt file:

target_link_libraries(${PROJECT_NAME} VStabiliser)

Done!

How to make custom implementation

The VStabiliser class provides only an interface, data structures, and methods for encoding and decoding commands and params. To create your own implementation of the video stabiliser, you must include the VStabiliser repository in your project (see Build and connect to your project section). The catalogue example (see Library files section) includes an example of the design of the custom video stabiliser. You must implement all the methods of the VStabiliser interface class. Custom video stabiliser class declaration:

class CustomVStabiliser: public VStabiliser
{
public:

    /// Class constructor.
    CustomVStabiliser();

    /// Class destructor.
    ~CustomVStabiliser();

    /// Get string of current class version.
    std::string getVersion();

    /// Init all video stabiliser params by params structure.
    bool initVStabiliser(VStabiliserParams& params);

    /// Set param.
    bool setParam(VStabiliserParam id, float value);

    /// Get param.
    float getParam(VStabiliserParam id);

    /// Get params.
    void getParams(VStabiliserParams& params);

    /// Execute command.
    bool executeCommand(VStabiliserCommand id);

    /// Stabilise video frame.
    bool stabilise(cr::video::Frame& src, cr::video::Frame& dst);

    /// Get offsets: horithontal, vertical and rotation.
    void getOffsets(float& dX, float& dY, float& dA);

    /// Decode and execute command.
    bool decodeAndExecuteCommand(uint8_t* data, int size);

private:

    /// Video stabiliser params (default params).
    VStabiliserParams m_params;
};