Hakim Benoudjit h4k1m0u

OSI model

For systems interconnections in a network, and has 7 layers (from top to bottom):

Application: Closest to user, e.g. HTTP, FTP...
Presentation: Encryption/Decryption, Compression/decompression, e.g. jpeg, mpeg...
Session: e.g. sync file transfers with checkpoints (to avoid restarting from beginning on failure).
Transport: Flow and error control, e.g. TCP, UDP
Network: breaks/assembleds data into packets, routing, e.g. IP
Data link: connects devices that are physically in the same network, e.g. Ethernet, MAC
Pyhsical: bit (raw data), e.g. cables

File format (binary) storing multiple instruments.
Stores instrument samples to play MIDI.
Samples are stored:
- For each note of an instrument (e.g. all piano keys).
- Possibly multiple velocities by key (how hard the note was struck).
[Polyphone][polyphone] can be used to read sf2 files.
[soundfont-fluid][soundfont-fluid] and [freepats-general-midi][freepats-general-midi] provide free samples in sf2 format (installed to /usr/share/soundfonts/).
Jack2: is an audio server like pulseaudio and alsa but professional audio production thanks to its low latency:

$ sudo pacman -Sy raylib

$ mkdir build
$ cd build
$ cmake .. &amp;&amp; make -j

Modes:
- Playback: Emit sound from speaker by writing data to output buffer (in callback).
- Capture: Extract sound from microphone by reading data from input buffer (in callback).
Sample: Single unit of audio data (when format = f32, a sample is a float in [-1, 1]).
Frame (PCM Frame): Groups of samples having as many samples as the number of channels (stereo: 1 frame = 2 samples, mono: 1 frame = 1 sample).
Sample rate: Number of frames processed each second expressed in Hz (e.g 44100 Hz).
Device: Abstraction for a physical device.
Callback: Function used to deliver data to/from the device async.
Data source: Used for retrieving audio data from a source (e.g. decoder, waveform for generrating sine waves...).
Decoder: Used for reading audio files (wav, mp3, flac).

From the [hello world example][hello-world]:

Coordinate system: y-axis points upwards and gravity downwards.
Units: meters, kilograms, and seconds
Area density: mass / area, and expressed in kg/m^2
Fixture: Used to attach a shape to the body
Shape: its coords are local to the body
Static body: mass ~> oo (stored = 0 in box2d)
Dynamic body: moves in response to forces
FPS: 60 frames/sec = freq => delta_t = 1/60 sec
Constraint solver: Iterates over constraints a number of times (two phases: velocity and position phases)

Interprocess communication (IPC) system for apps.
Runs as a service.
Two buses:
- System bus: e.g. to notify about hardware connect/disconnect. Its service: systemctl status dbus.
- Session bus: Specific to user sessions, e.g. communication between Gnome components. Its service: systemctl --user status dbus.
dbus-run-session <cmd>: Starts a new session bus and run cmd in that session (to have access to the session dbus for IPC):
- e.g gnome-shell --nested: Start Gnome within an existing session (for dev. & testing) without affecting the primary UI.

Conan2 was installed on Archlinux by building its [AUR package][conan-aur].
We follow Conan's [official docs][conan-getting-started] to setup CMake to use Conan:

$ conan install conanfile.txt --output-folder=build --build=missing
$ cd build
$ cmake -DCMAKE_TOOLCHAIN_FILE="conan_toolchain.cmake" ..
$ make -j

Query Youtube from a TUI & play videos using MPV

$ pip install yewtube
$ vim .bashrc
    export PATH="$PATH:...:/home/hakim/.local/bin"
$ yt

Project (bottom): Game assets (sprites, sounds, scripts, fonts...)
Hierarchy (left): Assets in scene (i.e. current level)
Inspector (right): Edit game object (position, rotation, scale, and to add components)
Coordinate system: Left-handed with y-up

Game objects: Scene objects (characters, props, scenery, camera...)
Components: Functional part of a game object, e.g. SpriteRenderer (A game objects can have multiple components)
Script class: Blueprint for creating a new component