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Terminology

A collection of terminology used throughout the project.

General

  • Streamer - The hardware platform responsible for capturing and streaming video (typically a Raspberry Pi Zero 2 W with a 4G modem).
  • Viewer - The computer or mobile device that receives the video stream from the streamer, displays it, and sends control data back.
  • Relay - A server used when the viewer does not have a fixed IP address (e.g., both devices are on mobile networks). The relay facilitates connectivity between the streamer and the viewer.
  • FPV (First-Person View) - A control method where the operator sees real-time video from the vehicle's perspective.

Networking

  • UDP (User Datagram Protocol) - The default transport protocol used for sending both video and control data. Prioritizes speed over reliability.
  • TCP (Transmission Control Protocol) - An alternative transport protocol available for relay connections. More reliable than UDP but slightly higher latency.
  • NAT (Network Address Translation) - The process of translating IP addresses to allow devices behind a router or modem to communicate with the internet.
  • CGNAT (Carrier-Grade NAT) - NAT applied at the mobile carrier level, meaning your device does not get a public IP address. This is why direct inbound connections to mobile devices are not possible and UDP hole punching or a relay is needed.
  • APN (Access Point Name) - A configuration parameter that tells your modem how to connect to the carrier's data network.
  • RNDIS (Remote Network Driver Interface Specification) - A protocol that allows 4G modems to present themselves as network devices to the host computer.
  • MNO (Mobile Network Operator) - A carrier that owns and operates its own mobile network infrastructure.
  • MVNO (Mobile Virtual Network Operator) - A carrier that provides mobile services by leasing network access from an MNO.
  • LTE (Long-Term Evolution) - The 4G mobile network standard used for data connectivity.
  • Cat 1 / Cat 4 - LTE modem categories defining maximum bandwidth. Cat 1 supports up to 10 Mbps down / 5 Mbps up. Cat 4 supports up to 150 Mbps down / 50 Mbps up.
  • SSH (Secure Shell) - A network protocol for secure remote access to the streamer's command line.
  • AP (Access Point) - A WiFi mode where the streamer creates its own wireless network for configuration when no known WiFi network is available.

Video

  • H.264 - The video codec used for encoding. It offers high compression efficiency, good quality at low bitrates, and is widely supported in hardware encoders.
  • I-frame (Intra-coded frame) - A complete video frame that can be decoded independently. Sent periodically to allow recovery from packet loss.
  • P-frame (Predicted frame) - A video frame that only contains changes from the previous frame, significantly reducing bandwidth usage.
  • QP (Quantization Parameter) - An encoder setting that controls the quality-to-bitrate tradeoff. Lower QP means higher quality but larger frames.
  • FPS (Frames Per Second) - The number of video frames captured and transmitted per second.
  • OSD (On-Screen Display) - The overlay on the viewer showing real-time telemetry such as latency, battery voltage, signal quality, and FPS.
  • GStreamer - An open-source multimedia framework used on the streamer for video capture, encoding, and streaming.
  • ISP (Image Signal Processor) - Hardware that processes raw camera sensor data into usable image formats.

Hardware

  • SBC (Single Board Computer) - A complete computer on a single circuit board, such as the Raspberry Pi.
  • ESC (Electronic Speed Controller) - A device that regulates power delivery to electric motors based on PWM input.
  • BEC (Battery Elimination Circuit) - A DC-DC voltage converter that provides stable 5V power to the Raspberry Pi from a battery.
  • PWM (Pulse Width Modulation) - A signal technique used to control servos and ESCs by varying the width of electrical pulses.
  • GPIO (General Purpose Input/Output) - Programmable digital pins on the Raspberry Pi that can be used as inputs or outputs.
  • CSI (Camera Serial Interface) - The ribbon cable interface on Raspberry Pi used to connect camera modules.
  • I2C (Inter-Integrated Circuit) - A two-wire serial communication protocol used for connecting sensors like the INA voltage monitor.
  • SDA / SCL - The data and clock lines of the I2C protocol.
  • INA - A Texas Instruments current/voltage measurement IC (e.g., INA226, INA231) used for battery monitoring.
  • UART (Universal Asynchronous Receiver-Transmitter) - A serial communication interface used for debugging and GPS connections.
  • VNA (Vector Network Analyzer) - Test equipment used to measure antenna impedance and performance.
  • SWR (Standing Wave Ratio) - A measurement of how well an antenna is matched to its transmission line. Lower SWR indicates better performance.

Software

  • Python - The programming language most of this project is written in. A custom build of Python is used on the streamer to ensure compatibility.
  • systemd - The Linux service manager used to start, stop, and monitor v3xctrl services on the streamer.
  • OverlayFS - A filesystem layer that makes the root partition read-only, protecting the SD card from corruption. Changes are stored in memory.
  • msgpack - A binary serialization format used for efficiently encoding control channel messages between streamer and viewer.