ScratchPad.md

Pragmatic: Concerned with practical matters Guided by practical experience and observation rather than theory

The Pragmatic Programmer

Tip-1: Care About Your Craft Tip-2: Think! About your work Tip-3: You have agency - You can change your organization or change your organization Tip-4: Provide options, don't make lame excuses Tip-5: Don’t Live with Broken Windows - Don’t leave "broken windows" (bad designs, wrong decisions, or poor code) unrepaired. Tip-6: Be a Catalyst for Change Tip-7: Remember the Big Picture Tip-8: Make Quality a Requirements Issue Tip-9: Invest Regularly in Your Knowledge Portfolio Tip-10: Critically Analyze What You Read and Hear Tip-11: English is Just Another Programming Language Tip-12: It's Both What You Say and the Way You Say It Tip-13: Build Documentation In, Don’t Bolt It On Tip-14: Good Design Is Easier to Change Than Bad Design Tip-15: DRY - Don't Repeat Yourself Tip-16: Make It Easy to Reuse Tip-17: Eliminate Effects Between Unrelated Things Tip-18: There Are No Final Decisions Tip-19: Forgo Following Fads Tip-20: Use Tracer Bullets to Find the Target Tip-21: Prototype to Learn Tip-22: Program Close to the Problem Domain Tip-23: Estimate to Avoid Surprises Tip-24: Iterate the Schedule with the Code Tip-25: Keep Knowledge in Plain Text (HTML, JSON, YAML, HTTP, SMTP, IMAP) Tip-26: Use the Power of Command Shells Tip-27: Achieve Editor Fluency Tip-28: Always Use Version Control Tip-29: Fix the Problem, Not the Blame Tip-30: Don't Panic Tip-31: Failing Test Before Fixing Code Tip-32: Read the Damn Error Message Tip-33: "select" Isn't Broken Tip-34: Don't Assume It - Prove It Tip-35: Learn a Text Manipulation Language [sed, awk, perl] Tip-36: You Can't Write Perfect Software Tip-37**: Design with Contracts (DBC) Tip-38: Crash Early Tip-39: Use Assertions to Prevent the Impossible Tip-40: Finish What You Start (Deallocate resource) Tip-41: Act Locally Tip-42: Take Small Steps - Always Tip-43: Avoid Foutune-Telling Tip-44: Decoupled Code Is Easier to Change Tip-45: Tell, Don't Ask Tip-46: Don't Chain Method Calls Tip-47: Avoid Global Data Tip-48: If It's Important Enough to Be Global, Wrap It in an API Tip-49: Programming Is About Code, But Programs Are About Data Tip-50: Don't Hoard State, Pass It Around Tip-51: Don't Pay Inheritance Tax Tip-52: Prefer Interfaces to Express Polymorphism Tip-53: Delegate to Services: Has-A Trumps Is-A Tip-54: Use Mixins to Share Functionality Tip-xx:

• The greatest of all weaknesses is the fear of apprearing weak.

• Entropy is a term from physics that refers to the amount of "disorder" in a system. Unfortunately, the laws of thermodynamics guarantee that the entropy in the universe tends toward a maximum.

• When disorder increases in software, we call it "software rot." (more optimistic term: "technical debt")

• hopelessness can be contagious, neglect accelerates the software rot faster than any other factor.

• Great software today is often preferable to the fantasy of perfect software tomorrow.

• Don't spoil a perfectly good program by overembellishment and overrefinement. Move on, and let your code stand in its own right for a while.

• software that suffers from feature bloat

• An investment in knowledge always pays the best interest. -- Benjamin Franklin

• Your ability to learn new things is your most important strategic asset. But how do you learn how to learn, and how do you know what to learn?

• Learn at least one new language every year

• Read a technical book each month

• A good idea is an orphan without effective communication.

• The meaning of your communication is the response you get

• Pragmatic Programmers embrace documentation as an integral part of the overall development process.

• ETC principle: Easier to Change.

• Every piece of knowledge must have a single, unambiguous, authoritative representation within a system

• Object-Oriented Software Construction [Mey97],

• the term "orthogonality" has come to signify a kind of independence or decoupling. Two or more things are orthogonal if changes in one do not affect any of the others

• Two or more things are orthogonal if changes in one do not affect any of the others.

• helicopters have four basic controls.

1. The cyclic is the stick you hold in your right hand. Move it, and the helicopter moves in the corresponding direction.
2. Your left hand holds the collective pitch lever. Pull up on this and you increase the pitch on all the blades, generating lift.
3. At the end of the pitch lever is the throttle.
4. Finally you have two foot pedals, which vary the amount of tail rotor thrust and so help turn the helicopter.

Decorator Pattern: adding functionality to things without changing them.

your code is easier to understand and maintain if you explicitly pass any required context into your modules.

In object-oriented applications, context is often passed as parameters to objects' constructors. In other code, you can create structures containing the context and pass around references to them.

• The term tracer bullet development refer to visually illustrate the need for immediate feedback under actual conditions with a moving goal.

• Human-readable forms of data, and self-describing data, will outlive all other forms of data and the applications thats created them.

• Bertrand Meyer (Object-Oriented Software Construction) developed the concept of Design by Contract for the language Eiffel.

  • Preconditions
  • Postconditions
  • Class invariants

• Don't use assertions in place of real error handling. Assertions check for things that should never happen.

• In the Observer Pattern, we have a source of events, called the observable and a list of clients, the observers, who are interested in those events.

• Publish/Subscribe (pubsub) generalizes the observer pattern, at the same time solving the problems of coupling and performance.

• Inheritance first appeared in Simula 67 in 1969.

• Three techniques that to replace inheritance

  • Interfaces and protocols
  • Delegation
  • Mixins and traits

• Mixin: The basic idea is simple: we want to be able to extend classes and objectes with new functionality without using inheritance.

Read-World Domain Language

• RSpec is a testing library for Ruby.

• Cucumber is a programming language neutral way of specifying tests.

• Phoenix Routes - Web framework for mapping incoming HTTP requests onto handler functions in the code.

• Ansible is a tool that configures software, typically on a bunch of remote servers.

• An object is a region of memory with a type that specifies what kind of information can be placed in it. A named object is called a variable.

• End-of-input character: (end of file) - On a Windows machine, that's Ctrl+Z followed by an Enter. On a Unix or Linux machine that's Ctrl+D.

Code Complete

================

• "Coding" isn't really the best word because it implies the mechanical translation of a preexisting design into a computer language; construction is not at all mechanical and involves substantial creativity and judgment

• In many projects, the only documentation available to programmers is the code itself.

• The most challenging part of programming is conceptualizing the problem, and many errors in programming are conceptual errors

• Fred Brooks’s The Mythical Man-Month

• A good craftsman knows the right tool for the job and knows how to use it correctly.

• Measure Twice, Cut Once

• The acronym "Cobol" stands for COmmon Business-Oriented Language.

• "Fortran" stands for FORmula TRANslation

C++

• std::enable_if_t<condition, type> evaluates to type if condition is true. Otherwise, the std::enable_if_t expression does not evaluate to anything.

• When the compiler sees different template functions with the same name and has to choose one of them, an important principle comes into play: SFINAE, which stands for Substitution Failure is not an Error. In this case, this means that the compiler does not error out if the return value of one of those functions cannot be deduced from an erroneous template expression (which std::enable_if is, in case its condition evaluates to false). It will simply look further and try the other function implementation. That is the trick; that is how this works.

If we use std::unordered_map instead of std::map, we have a different degree of freedom for the choice of the key type which shall be used.

std::unordered_map because it will not distinguish items via their smaller/greater ordering relationship but via hash values. The only thing we need to do is to implement a hash function for our own type, and an equal to == operator implementation, which tells whether two objects are identical

coroutines: suspend and resume with state preservation A concept is a set of requirements on a set of template arguments. A concept is a compile-time predicate

diamond of death pattern in the class hierarchy

With virtual inheritance, we can make sure that a parent class only appears in any children classes once. To implement virtual inheritance, we simply use the virtual keyword when declaring the class we want to inherit from.

The first potential drawback is that all templates must have their entire implementation in the same file, usually the header.

OpenGL

For building Win32 application using CMake use the following command cmake -S. -Bb -A Win32 cmake --build release --config release // for release build

there exist both different versions of OpenGL and different variants of OpenGL. For example, in addition to "standard OpenGL" (sometimes called "desktop OpenGL"), there exists a variant called "OpenGL ES," which is tailored for development of embedded systems (hence the "ES"). "Embedded systems" include devices such as mobile phones, game consoles, automobiles, and industrial control systems. OpenGL ES is mostly a subset of standard OpenGL, eliminating a large number of operations that are typically not needed for embedded systems.

another variant of OpenGL is called "WebGL" Based on OpenGL ES, WebGL is designed to support the use of OpenGL in web browsers. WebGL allows an application to use JavaScript1 to invoke OpenGL ES operations, which makes it easy to embed OpenGL graphics into standard HTML (web) documents

mathematics library called GLM.

SOIL2 library is used for loading and processing texture image files.

graphics programming is shader based that is, some of the program is written in a standard language such as C++ or Java for running on the CPU and some is written in a special-purpose shader language for running directly on the graphics card (GPU).

There are many graphics libraries in use today, but the most common library for platfor mindependent graphics programming is called OpenGL (Open Graphics Library).

In 2006 the ARB transferred control of the OpenGL specification to the Khronos Group, a nonprofit consortium which manages not only the OpenGL specification but a wide variety of other open industry standards.

In 2004, version 2.0 introduced the OpenGL Shading Language (GLSL), allowing "shader programs" to be installed and run directly in graphics pipeline stages.

In 2009, version 3.1 removed a large number of features that had been deprecated,

version 4.0 (in 2010) added a tessellation stage to the programmable pipeline.

OpenGL doesn't actually draw to a computer screen. Rather, it renders to a frame buffer, and it is the job of the individual machine to then draw the contents of the frame buffer onto a window on the screen.

One of the most popular options, and the one used in this book, is GLFW (Graphics Library Framework), which has built-in support for Windows, Macintosh, Linux, and other systems

GLFW is an Open Source, multi-platform library for OpenGL, OpenGL ES and Vulkan development on the desktop. It provides a simple API for creating windows, contexts and surfaces, receiving input and events. GLFW is written in C and supports Windows, macOS, X11 and Wayland.

Extension libraries: Glee, GLLoader, GLEW (OpenGL Extension Wrangler), and more recently GL3W and GLAD.

Two math libraries that are frequently used with OpenGL are Eigen and vmath,

GLM (OpenGL Mathematics). It is a header-only C++ library compatible with Windows, Macintosh, and Linux

Texture loading libraries FreeImage, DevIL, OpenGL Image (GLI), and Glraw.

Probably the most commonly used OpenGL image loading library is Simple OpenGL Image Loader (SOIL), although it has become somewhat outdated.

On the hardware side, OpenGL provides a multi-stage graphics pipeline that is partially programmable using a language called GLSL (OpenGL Shading Language).

One important task of a C++/OpenGL application is to install the programmer’s GLSL code onto the GPU.

There are other shader languages, such as HLSL, which works with Microsoft's 3D framework DirectX.

OpenGL is capable of drawing only a few kinds of very simple things, such as points, lines, or triangles. These simple things are called primitives,

OpenGL still requires that at least one VAO (Vertex Array Objects) be created whenever shaders are being used, even if the application isn't using any buffers. So the two lines create the required VAO.

The programmable tessellation stage is one of the most recent additions to OpenGL (in version 4.0). It provides a tessellator that can generate a large number of triangles, typically as a grid, and also some tools to manipulate those triangles in a variety of ways

Whereas the vertex shader gives the programmer the ability to manipulate one vertex at a time (i.e., "pervertex" processing), and the fragment shader (as we will see) allows manipulating one pixel at a time ("per-fragment" processing), the geometry shader provides the capability to manipulate one primitive at a time "per-primitive" processing.

our 3D world of vertices, triangles, colors, and so on needs to be displayed on a 2D monitor. That 2D monitor screen is made up of a raster - a rectangular array of pixels.

the purpose of the fragment shader is to assign colors to the rasterized pixels.

hidden surface removal, or HSR. OpenGL can perform a variety of HSR operations, depending on the effect we want in our scene.

Hidden surface removal is accomplished by OpenGL through the cleverly coordinated use of two buffers: the color buffer (which we have discussed previously), and the depth buffer (sometimes called the Z-buffer).

Points in homogeneous notation contain four values. The first three correspond to X, Y, and Z, and the fourth, W, is always a fixed nonzero value, usually 1.

OpenCV

OpenCV is an open source library containing more than 500 optimized algorithms for image and video analysis.

OpenCV was originally developed at Intel

1999 - Started 2006 - version 1.0 2009 - version 2.0 introduce c++ interface 2012 - non-profit foundation 2013 - version 3.0 (improve usability of library, large module split into smaller one)

• opencv_core module that contains the core functionalities of the library, in particular, basic data structures and arithmetic functions

• opencv_imgproc module that contains the main image-processing functions

• opencv_highgui module that contains the image and video reading and writing functions along with some user interface functions

• opencv_features2d module that contains the feature point detectors and descriptors and the feature point matching framework

• opencv_calib3d module that contains the camera calibration, two-view geometry estimation, and stereo functions

• opencv_video module that contains the motion estimation, feature tracking, and foreground extraction functions and classes

• opencv_objdetect module that contains the object detection functions such as the face and people detectors

machine learning functions (opencv_ml), computational geometry algorithms (opencv_flann), contributed code (opencv_contrib) opencv_photo for computational photography opencv_stitching for image-stitching algorithms

old notes

packages required for opencv key libraries used by opencv

build-essential cmake git pkg-config

libraries reading image format libjpeg8-dev libtiff5 libjasper-dev libpng12-dev

video codec format libavcodec-dev libavformat-dev libswscale-dev libv4l-dev

user interface feature libgtk2.0-dev

optimize opencv command libatlas-base-dev gfortran

Core Concepts

C:\Users\Aamir\AppData\Local\Programs\Python\Python37\Lib\site-packages\numpy\core\include

OpenCV 4.3.0 build failing on generating vs_version.rc using mingw-w64 Ans: Hi @alalek adding the -DOPENCV_ALLOCATOR_STATS_COUNTER_TYPE=int64_t option to CMAKE allows the build to complete.

dense multidimensional array, Mat Image Process include

• filtering (linear and nonlinear)
• geometric transformations
• color space conversion ...

machine learning tools such as

• statistical classification
• regression
• data clustering

OpenCV Mat class is used for dense n-dimensional single or multichannel array.

Given an image matrix, we can find the derivative using another matrix called maskor kernel.

Python for Microscopists by Sreeni

Popular Linux Desktop Environments:

1. GNOME Shell
2. KDE Plasma Desktop
3. LXQt
4. Cinnamon
5. MATE
6. Xfce

tree -L 1 htop

Bash, Zsh, csh, fish and ksh

BusyBox alternative to GNU coreutils (its a single program)

Filesysten Huerarchy Standard (FHS)

/etc system configuration /var changable variable system information stored like logs dev, proc, sys -> created by kernel

chmod chrgrp

SELinux AppArmor

Package managers: ATP, dnf, apk, zypper System manager - systemd or SysVinit Debian doesn't include sudo (but can be installed)

cat /etc/*release

Arch or Alpine Linux List of Linux distributions (wikipedia)

kuler.adobe.com /etc/wsl.conf [network] name=myWSL

wslpath -> convert path between Windows and Linux

C# and .Net Essential Programming

dotnet --version dotnet --list-sdks

Free, cross-platform, open-source developer platform .NET provides: Core Services Languages CLR

Create new console app dotnet new console -n -f "net6.0"

starting with .net6 some common library are automatically included implicit using directives

using System; using System.IO; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Threading; using System.Threading.Tasks;

Value Types: enum, structs and tuples Reference Types: objects, strings and records

String methods: Strings are inmutable

Equals Compare Join('c', ); Join("string"); Replace(); Contains();

dotnet workload search dotnet workload list dotnet workload install dotnet workload update dotnet workload repair

Base Class Library (BCL) NuGet Package Management (Modular functionality)

C# 10.0

Namespace Management global using System.Text.RegularExpression

Linux Kernel

kernel name like vmlinuz- boot loader, like GRUB

virtual file systems:

• proc
• sys
• debugfs

Loadable kernel modules

Commands for HW info

lshw and lspci lsusb and lsbk lscpu and lsdev

Linux system call list: include/uapi/asm-generic/unistd.h

documented in man section 2 !$: last output of last line

man 1: user commands man 2: linux programmer's manual

printk() is kernel's function for code to print message - sent to RAM buffer sysctl -a

GStreamer

GStream: multimedia framework (for media application) to get access to graphics hardware (codec shipped with intel cpu, integrated graphics) gstreamer has plugin architecutre

Intel Media SDK for Intel Graphics Hardware Scriptable Command Line Tools

gst-inspect gst-launch gst-editor

CUDA core is a technology from NVidia. Allows using GPU hardware as generic computer.

gst-discover => gives information about the file

Transcode => un-encode -> process -> decode

.NET-6 Deep Dive

C++ Design Patterns: Behavioral

Design Pattern: Solution to very common problems in object oriented programming (in code organization) anti-patterns: harmful pattern

12 Behavioral Design Patterns

1. Chain of Responsibility
2. Command
3. Mediator
4. Observer
5. Interpreter
6. State
7. Strategy
8. Template Method
9. Visitor
10. Iterator
11. Memento
12. Null-Object

C++ Concurrent Programming

Flynn's Taxonomy - Parellel hardware Clasifying multip processor architecture SISD Single Instruction Single Data SIMD Single instruction multiple data (GPU USES simd) MISD Multiple instruction single data MIMD Multiple instruction multiple data (most important)

SPMD: single program multiple data MPMD: multiple program multiple data

shared memory: All processors share same memory distrubuted memory:

Concurrency vs Parallelism Program structure Simultaneous execution

Preemptive vs non preemptive schecduling algorithm

data race: The operation to aquire a mutex is atomic operation atomic operation is uninterrupted

reenterant or recursive mutex

reader-writer lock

shared mutex - technically uses more resources shared read by multiple threads at once exclusive write - only one thread at a time

std::shared_mutex marker
marker.lock_shared();    // shared read lock
marker.unlock_shared();

marker.lock();     // exclusive write lock
marker.unlock();

CMake

• CMake and its siblings, CTest, CPack and CDash leading toolset for building software from source.

• CMake's goal was to provide a set of tools that would make it easier to configure, build, test, and deploy the same project across different platforms.

• CMake is a build-system generator, offering a powerful domain-specific language (DSL) to describe what the build system should achieve.

• The Ninja program is a different build-automation tool that works on GNU/Linux, macOS and Windows. Ninja is a new build tool, with a focus on speed, especially for incremental rebuilds.

Linux Command Line

• To see the current amount of free space on disk: df -h

• To display the amount of free memory: free

• cd shortcuts

cd # changes the working directory to home directory
cd - # Changes the working directory to previous working directory
cd ~user_name # Changes the working directory to home directory of user_name

• ls ~ /usr - We can specify multiple directories to ls

• ls options: -l long format output -t sort the result by file's modification time --reverse to reverse the order of sort

• Use file command to determine a file's type.

• The less command is a program to view text file.

• The less program was designed as an improved replacement of an earlier Unix program called more

a symbolic link (also known as a soft link or symlink). In most Unix-like systems, it is possible to have a file referenced by multiple names.

• Nautilus file manager for GNOME

• Dolphin and Konqueror - File manager for KDE.

• Hard links are the original Unix way of creating links, compared to symbolic

• Hard links have two important limitations.

  • A hard link cannot reference a file outside its own file system. This means a link cannot reference a file that is not on the same disk partition as the link itself.
  • A hard link may not reference a directory.

• Symbolic links create a special type of file that contains a text pointer to the referenced file or directory. links, which are more modern

• type - Display a command's type (external/shell builtin etc)

• which - Display an executable's location (which only works for executables)

• whatis - Display one line manual page descriptions

• The GNU Project provides an alternative to man pages for their programs, called info

• The gzip package includes a special version of less called zless that will display the contents of gzip compressed text files

• It's possible to put more than one command on a line by separating each command with a semicolon

• alias foo='cd /usr; ls; cd -'

• unalias foo

• if we ever need to actually truncate a file (or create a new, empty file), we can use a trick > out.txt

• Redirecting Standard Output and Standard Error to One File ls -l /usr/bin > output.txt 2>&1

• Recent versions of bash provide a second, more streamlined method ls -l /usr/bin &> output.txt ls -l /bin/usr &>> out.txt

• wildcards always expand in sorted order

• The uniq command is often used in conjunction with sort command. uniq accepts a sorted list of data from either standard input or a single filename argument and, by default, removes any duplicates from the list.

• grep is a powerful program used to find text patterns within files

• The head command prints the first 10 lines of a file, and the tail command prints the last 10 lines.

• tail has an option that allows you to view files in real time. tail -f /var/log/messages

• Linux provides a command called tee that creates a "tee" fitting on our pipe. The tee program reads standard input and copies it to both standard output (allowing the data to continue down the pipeline) and to one or more files.

• ls /usr/bin | tee ls.txt | grep zip

• echo is a shell builtin that performs a very simple task. It prints its text arguments on standard output

• The shell allows arithmetic to be performed by expansion $((expression))

• Perhaps the strangest expansion is called brace expansion. With it, you can create multiple text strings from a pattern containing braces

echo Front-{A,B,C}-Back
Front-A-Back Front-B-Back Front-C-Back

echo Number_{1..5}
echo {01..15}

• Command substitution allows us to use the output of a command as an expansion. echo $(ls) ls -l $(which cp)

• Adding the -e option to echo will enable interpretation of escape sequences. You can also place them inside $' '.

• bash uses a library (a shared collection of routines that different programs can use) called Readline to implement command line editing.

• To find out information about your identity, use the id command.

a namespace is a declaration that provides scope for all the variables, types, and functions inside of its encapsulation.

What makes inheritance even more powerful is the fact that we not only can adopt the functions of the inherited class, we can override them with our own implementations.

The protectd methods and variables are only available to the class itself and any classes derived.

With virtual inheritance, we can make sure that a parent class only appears in any children classes once.

class Boss : public virtual Enemy {}
class FlyingEnemy : public virtual Enemy {}
class FlyingBoss : public Boss, public FlyingEnemy {}  // only one copy of Enemy class

polymorphism is the ability to use an object of a class as if it was part of another class.

By default, const objects cannot call non const functions. However, non non objects can still call const functions.

the list container does not store all its elements in one large contiguous block of memory. Instead, it stores its elements as nodes in a doubly linked list.

Unlike sequence containers, associative containers do not preserve the relative positions of the elements in them. Instead associative containers are built for speed, more specifically element lookup speed.

As of the C++14 standard, there are now three types of templates that can be used: class templates, function templates, and variable templates.

The first potential drawback is that all templates must have their entire implementation in the same file, usually the header.

Another drawback of templates is that they are notorious for being hard to debug. Compilers tend to give cryptic errors when the issue resides inside of the templated code.

The auto keyword has a helper keyword, decltype, which extracts the type from a variable. So where auto is used to let the compiler infer what the variable type is, the decltype is utilized to determine what a variable's type is.

Run-time type information (RTTI), which is the concept of determining the type of a variable at runtime.

A somewhat more ideal solution would be to have an EventHandler class that would handle the registration, storage, and polymorphic functions for all events.

cl /c hello.cpp
lib /out:MyLib.lib hello.obj
cl main.cpp /link MyLib.lib

// using gcc on Linux/MacOS
gcc -c hello.cpp
ar rvs MyLib.a hello.o
g++ main.cpp MyLib.a -o main

Dynamic or shared libraries are libraries that have their code implementations linked at runtime.

For dynamic or shared libraries, we have to make a few modifications and follow slightly different steps for compilation and linking. To begin with, we will have to change our library file to let the compiler know that we would like to share certain parts with other programs. We do this, on the Microsoft platform, with __declspec or declaration specification. Passing the dllexport parameter to __declspec lets the compiler know that this function or even classes should be exported as part of the dynamic linked library. On the OS X platform, we also use a type of declaration to let the compiler know that the classes or functions are to be exported. Here we use __attribute__((visibility("default"))) in place of __declspec

For creating dynamic link library on Windows

cl /LD /FeMyDynamicLib.dll hello.cpp

/LD - Create dynamically linked library

The .lib of a dynamic library acts as a pointer to the actual implementation in the .dll file

In Linker select Input. At the top of the dialog on the Additional Dependencies property, click on the drop down and select Edit. we specify the libraries we wish to include at compile time. We include .lib file regardless of whether it is a dynamic library or static library.

Macros: $(SolutionDir) This is the top solution directory $(SourceDir) This is the directory of the source for the project $(Platform) This is the platform that is selected (Win32, x64, ARM) $(Configuration) This is the configuration that is selected (Debug/Release)

• OpenGL (https://www.opengl.org/): The Open Graphics Library (OGL) is an open cross-language, cross-platform application programming interface, or API, used for rendering 2D and 3D graphics. The API provides low-level access to the Graphics Processing Unit (GPU). SDL (https://www.libsdl.org/): The Simple DirectMedia Layer (SDL) is a cross-platform software development library designed to deliver a low-level hardware abstraction layer to multimedia hardware components. While it does provide its own mechanism for rendering, SDL can use OGL to provide full 3D rendering support.

An OGL context can be thought of as a set of states that describes all the details related to the rendering of the application. The OGL context must be set before any drawing can be done.

FFmpeg implements almost all the common data encapsulation formats, multimedia transmission protocol and audio and video codecs.

FFmpeg is functionally divided into several modules: * libutils - core tools * libavformat - media formats * libavcodec - codecs * libavdevice - devices * libavfilter, libswscale, libpostproc - post-processing