VFilter C++ interface library

v1.1.3

Overview

VFilter C++ library provides interface as well defines data structures for various video filters implementations. The VFilter interface represents video filter module which has video frames as input and output. The VFilter.h file contains declaration of data structures: VFilterCommand enum, VFilterParam enum, VFilterParams class and VFilter class declaration. The library depends on Frame library (describes data structures for video frames, source code included, Apache 2.0 license) and ConfigReader library (provides methods to read/write JSON config files, source code included, Apache 2.0 license). The library uses C++17 standard and doesn't have third-party dependencies to be installed in OS. The library is licensed under the Apache 2.0 license.

Versions

Table 1 - Library versions.

Version	Release date	What's new
1.0.0	20.02.2024	First version of the library.
1.1.0	22.02.2024	- Added setMask(...) method. - Added initVFilter(...) to initialize video filter. - Documentation updated.
1.1.1	25.02.2024	- Parameter processingTimeMcSec excluded from JSON to read / write.
1.1.2	24.03.2024	- Frame class updated. - ConfigReader class updated. - Documentation updated.
1.1.3	21.05.2024	- Submodules 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 to includes third-party libraries.
    ConfigReader --------------- Folder with ConfigReader library source code.
    Frame ---------------------- Folder with Frame library source code.
src ---------------------------- Folder with source code of the library.
    CMakeLists.txt ------------- CMake file of the library.
    VFilter.cpp ---------------- C++ implementation file.
    VFilter.h ------------------ Main header file of the library.
    VFilterVersion.h ----------- Header file which includes version of the library.
    VFilterVersion.h.in -------- Service CMake file to generate version file.
test --------------------------- Folder for the test application.
    CMakeLists.txt ------------- CMake file for the test application.
    main.cpp ------------------- Source code file of the test application.
example ------------------------ Folder with source code of the custom VFilter implementation.
    CMakeLists.txt ------------- CMake file of the library.
    CustomVFilter.cpp ---------- Source code file of the library.
    CustomVFilter.h ------------ Header file which includes CustomVFilter class declaration.
    CustomVFilterVersion.h ----- Header file which includes version of the library.
    CustomVFilterVersion.h.in -- CMake service file to generate version file.

VFilter interface class description

VFilter interface class declaration

The VFilter interface class declared in VFilter.h file. Class declaration:

class VFilter
{
public:

    /// Class destructor.
    virtual ~VFilter();

    /// Get the version of the VFilter class.
    static std::string getVersion();

    /// Initialize video filter.
    virtual bool initVFilter(VFilterParams& params) = 0;

    /// Set the value for a specific library parameter.
    virtual bool setParam(VFilterParam id, float value) = 0;

    /// Get the value of a specific library parameter.
    virtual float getParam(VFilterParam id) = 0;

    /// Get the structure containing all library parameters.
    virtual void getParams(VFilterParams& params) = 0;

    /// Execute a VFilter action command.
    virtual bool executeCommand(VFilterCommand id) = 0;

    /// Process frame.
    virtual bool processFrame(cr::video::Frame& frame) = 0;

    /// Set mask for filter.
    virtual bool setMask(cr::video::Frame mask) = 0;

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

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

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

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

getVersion method

The getVersion() static method returns string of current class version. Method declaration:

static std::string getVersion();

Method can be used without VFilter class instance:

std::cout << "VFilter version: " << cr::video::VFilter::getVersion();

Console output:

VFilter class version: 1.1.3

initVFilter method

The initVFilter(...) method initializes video filter. Particular video filter class should initialize only supported parameters from VFilterParams class. Method declaration:

virtual bool initVFilter(VFilterParams& params) = 0;

Parameter	Value
params	VFilterParams class object. Particular video filter class may not support all params listed in VFilterParams class. If video filter doesn't support particular params, those params should have default values.

Returns: TRUE if the video filter initialized or FALSE if not.

setParam method

The setParam (...) method sets new parameters value. VFilter based library should provide thread-safe setParam(...) method call. This means that the setParam(...) method can be safely called from any thread. Method declaration:

virtual bool setParam(VFilterParam id, float value) = 0;

Parameter	Description
id	Parameter ID according to VFilterParam enum.
value	Parameter value. Value depends on parameter ID.

Returns: TRUE if the parameter was set or FALSE if not.

getParam method

The getParam(...) method returns parameter value. VFilter based library should provide thread-safe getParam(...) method call. This means that the getParam(...) method can be safely called from any thread. Method declaration:

virtual float getParam(VFilterParam id) = 0;

Parameter	Description
id	Parameter ID according to VFilterParam enum.

Returns: parameter value or -1 if the parameters doesn't exist (not supported in particular implementation).

getParams method

The getParams(...) method is designed to obtain all video filter params. VFilter based library should provide thread-safe getParams(...) method call. This means that the getParams(...) method can be safely called from any thread. Method declaration:

virtual void getParams(VFilterParams& params) = 0;

Parameter	Description
params	Reference to VFilterParams object to store params.

executeCommand method

The executeCommand(...) method executes video filter action command. VFilter based library should provide thread-safe executeCommand(...) method call. This means that the executeCommand(...) method can be safely called from any thread. Method declaration:

virtual bool executeCommand(VFilterCommand id) = 0;

Parameter	Description
id	Command ID according to VFilterCommand enum.

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

processFrame method

The processFrame(...) method designed to process frame. VFilter based library should provide thread-safe processFrame(...) method call. This means that the processFrame(...) method can be safely called from any thread. Method declaration:

virtual bool processFrame(cr::video::Frame& frame) = 0;

Parameter	Description
frame	Reference to Frame object. Particular video filter implementation must keep original video frame resolution (width and height), sourceId and frameId fields.

Returns: TRUE if frame processed or FALSE if not. If filter disabled the method should return TRUE without video frame processing.

setMask method

The setMask(...) method designed to set video filter mask. Method declaration:

virtual bool setMask(cr::video::Frame mask) = 0;

Parameter	Description
mask	Filter mask is Frame object with GRAY pixel format. Filter omits image segments, where filter mask pixel values equal 0.

Returns: TRUE if the filter mask was set or FALSE if not.

encodeSetParamCommand method

The encodeSetParamCommand(...) static method encodes command to change any VFilter parameter value. To control any video filter remotely, the developer has to design his own protocol and according to it encode the command and deliver it over the communication channel. To simplify this, the VFilter class contains static methods for encoding the control command. The VFilter 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, VFilterParam 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 VFilterParam enum.
value	Parameter value.

encodeSetParamCommand(...) is static and used without VFilter class instance. This method used on client side (control system). Command encoding example:

// Buffer for encoded data.
uint8_t data[11];
// Size of encoded data.
int size = 0;
// Random parameter value.
float outValue = static_cast<float>(rand() % 20);
// Encode command.
VFilter::encodeSetParamCommand(data, size, VFilterParam::LEVEL, outValue);

encodeCommand method

The encodeCommand(...) static method encodes command for VFilter remote control. To control any video filter remotely, the developer has to design his own protocol and according to it encode the command and deliver it over the communication channel. To simplify this, the VFilter class contains static methods for encoding the control command. The VFilter 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, VFilterCommand id);

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

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

// Buffer for encoded data.
uint8_t data[7];
// Size of encoded data.
int size = 0;
// Encode command.
VFilter::encodeCommand(data, size, VFilterCommand::RESTART);

decodeCommand method

The decodeCommand(...) static method decodes command on image filter side. Method declaration:

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

Parameter	Description
data	Pointer to input command.
size	Size of command. Must be 11 bytes for SET_PARAM and 7 bytes for COMMAND.
paramId	VFilter parameter ID according to VFilterParam enum. After decoding SET_PARAM command the method will return parameter ID.
commandId	VFilter command ID according to VFilterCommand enum. After decoding COMMAND the method will return command ID.
value	VFilter 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.

decodeAndExecuteCommand method

The decodeAndExecuteCommand(...) method decodes and executes command encoded by encodeSetParamCommand(...) and encodeCommand(...) methods on video filter side. The particular implementation of the VFilter 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

VFilterCommand enum

Enum declaration:

enum class VFilterCommand
{
    /// Reset image filter algorithm.
    RESET = 1,
    /// Enable filter.
    ON,
    /// Disable filter.
    OFF
};

Table 2 - Action commands description.

Command	Description
RESET	Reset image filter algorithm.
ON	Enable video filter.
OFF	Disable video filter.

VFilterParam enum

Enum declaration:

enum class VFilterParam
{
	/// Current filter mode, usually 0 - off, 1 - on.
	MODE = 1,
	/// Enhancement level for particular filter, as a percentage in range from 
	/// 0% to 100%.
	LEVEL,
	/// Processing time in microseconds. Read only parameter.
	PROCESSING_TIME_MCSEC,
	/// Type of the filter. Depends on the implementation.
	TYPE,
	/// VFilter custom parameter. Custom parameters used when particular image 
	/// filter has specific unusual parameter.
	CUSTOM_1,
	/// VFilter custom parameter. Custom parameters used when particular image 
	/// filter has specific unusual parameter.
	CUSTOM_2,
	/// VFilter custom parameter. Custom parameters used when particular image 
	/// filter has specific unusual parameter.
	CUSTOM_3
};

Table 3 - Params description.

Parameter	Access	Description
MODE	read / write	Current filter mode, usually 0 - off, 1 - on (typical). Can have another meaning depends on implementation.
LEVEL	read / write	Enhancement level for particular filter, as a percentage in range from 0% to 100% (typical). Can have another meaning depends on implementation. The video filter should keep this value in memory. After enable video filter this value should be implemented.
PROCESSING_TIME_MCSEC	read only	Processing time in microseconds. Read only parameter. Used to control performance of video filter.
TYPE	read / write	Type of the filter. Depends on the implementation.
CUSTOM_1	read / write	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.
CUSTOM_2	read / write	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.
CUSTOM_3	read / write	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.

VFilterParams class description

VFilterParams class declaration

The VFilterParams class is used to provide video filter parameters structure. Also VFilterParams provides possibility to write/read params from JSON files (JSON_READABLE macro) and provides methods to encode and decode params. VFilterParams interface class declared in VFilter.h file. Class declaration:

class VFilterParams
{
public:
    /// Current filter mode, usually 0 - off, 1 - on.
    int mode{ 0 };
    /// Enhancement level for particular filter, as a percentage in range from 
    /// 0% to 100%.
    float level{ 0 };
    /// Processing time in microseconds. Read only parameter.
    int processingTimeMcSec{ 0 };
    /// Type of the filter. Depends on the implementation.
    int type{ 0 };
    /// VFilter custom parameter. Custom parameters used when particular image 
    /// filter has specific unusual parameter.
    float custom1{ 0.0f };
    /// VFilter custom parameter. Custom parameters used when particular image 
    /// filter has specific unusual parameter.
    float custom2{ 0.0f };
    /// VFilter custom parameter. Custom parameters used when particular image 
    /// filter has specific unusual parameter.
    float custom3{ 0.0f };

    /// Macro from ConfigReader to make params readable/writable from JSON.
    JSON_READABLE(VFilterParams, mode, level, type, custom1, custom2, custom3)

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

    // Encode (serialize) params.
    bool encode(uint8_t* data, int bufferSize, int& size,
                                             VFilterParamsMask* mask = nullptr);
	// Decode (deserialize) params.
    bool decode(uint8_t* data, int dataSize);
};

Table 4 - VFilterParams class fields description is related to VFilterParam enum description.

Field	type	Description
mode	int	Current filter mode, usually 0 - off, 1 - on (typical). Can have another meaning depends on implementation.
level	float	Enhancement level for particular filter, as a percentage in range from 0% to 100% (typical). Can have another meaning depends on implementation. The video filter should keep this value in memory. After enable video filter this value should be implemented.
processingTimeMcSec	int	Processing time in microseconds. Read only parameter. Used to control performance of video filter.
type	int	Type of the filter. Depends on the implementation.
custom1	float	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.
custom2	float	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.
custom3	float	VFilter custom parameter. Custom parameters used when particular image filter has specific unusual parameter.

None: VFilterParamsclass fields listed in Table 4 have to reflect params set/get by methods setParam(...) and getParam(...).

Serialize VFilter params

VFilterParams class provides method encode(...) to serialize VFilter params. Serialization of VFilterParams is necessary in case when image filter parameters have to be sent via communication channels. Method provides options to exclude particular parameters from serialization. To do this method inserts binary mask (1 byte) where each bit represents particular parameter and decode(...) method recognizes it. Method declaration:

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

Parameter	Value
data	Pointer to data buffer. Buffer size must be >= 48 bytes.
bufferSize	Data buffer size. Buffer size must be >= 48 bytes.
size	Size of encoded data.
mask	Parameters mask - pointer to VFilterParamsMask structure. VFilterParamsMask (declared in VFilter.h file) determines flags for each field (parameter) declared in VFilterParams 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 VFilterParamsMask structure.

Returns: TRUE if params encoded (serialized) or FALSE if not.

VFilterParamsMask structure declaration:

struct VFilterParamsMask
{
    bool mode{ true };
    bool level{ true };
    bool processingTimeMcSec{ true };
    bool type{ true };
    bool custom1{ true };
    bool custom2{ true };
    bool custom3{ true };
};

Example without parameters mask:

// Prepare parameters.
cr::video::VFilterParams params;
params.level = 80.0f;

// Encode (serialize) params.
int bufferSize = 128;
uint8_t buffer[128];
int size = 0;
params.encode(buffer, bufferSize, size);

Example with parameters mask:

// Prepare parameters.
cr::video::VFilterParams params;
params.level = 80.0;

// Prepare mask.
cr::video::VFilterParams mask;
// Exclude level.
mask.level = false;

// Encode (serialize) params.
int bufferSize = 128;
uint8_t buffer[128];
int size = 0;
params1.encode(buffer, bufferSize, size, &mask);

Deserialize VFilter params

VFilterParams class provides method decode(...) to deserialize params. Deserialization of VFilterParams is necessary in case when it is needed 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 with serialized params.
dataSize	Size of command data.

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

Example:

// Prepare parameters.
cr::video::VFilterParams params1;
params1.level = 80;

// Encode (serialize) params.
int bufferSize = 128;
uint8_t buffer[128];
int size = 0;
params1.encode(buffer, bufferSize, size);

// Decode (deserialize) params.
cr::video::VFilterParams params2;
params2.decode(buffer, size);

Read params from JSON file and write to JSON file

VFilter depends on open source 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:

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

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

VFilterParams.json will look like:

{
    "vFilterParams":
    {
        "level": 50,
        "mode": 2,
        "processingTimeMcSec": 23,
        "type": 1,
        "custom1": 0.7,
        "custom2": 12.0,
        "custom3": 0.61
    }
}

Build and connect to your project

Typical commands to build VFilter:

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

If you want connect VFilter 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 VFilter as submodule by commands:

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

In your repository folder will be created folder 3rdparty/VFilter which contains files of VFilter repository with subrepository ConfigReader. New structure of your repository:

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

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(${PARENT}_SUBMODULE_VFILTER                         ON  CACHE BOOL "" FORCE)
if (${PARENT}_SUBMODULE_VFILTER)
    SET(${PARENT}_VFILTER                               ON  CACHE BOOL "" FORCE)
    SET(${PARENT}_VFILTER_TEST                          OFF CACHE BOOL "" FORCE)
    SET(${PARENT}_VFILTER_EXAMPLE                       OFF CACHE BOOL "" FORCE)
endif()

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

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

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

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 VFilter library in your src/CMakeLists.txt file:

target_link_libraries(${PROJECT_NAME} VFilter)

Done!

How to make custom implementation

The VFilter class provides only an interface, data structures, and methods for encoding and decoding commands and params. To create your own implementation of the video filter, VFilter repository has to be included 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 VFilter algorithm. All the methods of the VFilter interface class have to be included. Custom VFilter class declaration:

class CustomVFilter : public VFilter
{
public:

    // Class constructor.
    CustomVFilter();

    // Class destructor.
    ~CustomVFilter();

    // Get the version of the VFilter class.
    static std::string getVersion();
    
    //  Initialize video filter. 
    bool initVFilter(VFilterParams& params) override;
    
 	// Set the value for a specific library parameter.
    bool setParam(VFilterParam id, float value) override;

    // Get the value of a specific library parameter.
    float getParam(VFilterParam id) override;

    // Get the structure containing all library parameters.
    void getParams(VFilterParams& params) override;

    // Execute a VFilter command.
    bool executeCommand(VFilterCommand id) override;

    // Process frame.
    bool processFrame(cr::video::Frame& frame) override;

    // Set mask.
    bool setMask(cr::video::Frame mask) override;

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

private:

    /// Parameters structure (default params).
    VFilterParams m_params;
    /// Mutex for parameters access.
    std::mutex m_paramsMutex;
};

Name		Name	Last commit message	Last commit date
Latest commit History 28 Commits
3rdparty		3rdparty
example		example
src		src
static		static
test		test
.gitignore		.gitignore
.gitmodules		.gitmodules
CMakeLists.txt		CMakeLists.txt
LICENSE		LICENSE
README.md		README.md
VFilter_interface_C++_library_v1.1.3.pdf		VFilter_interface_C++_library_v1.1.3.pdf

License

ConstantRobotics-Ltd/VFilter

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