Home¶
Welcome to the videosynth documentation. Here you will find the user manual and the complete project-file reference for videosynth.
What is videosynth?¶
videosynth is a video signal synthesizer for PAL, PAL-M, NTSC and SECAM. It generates analogue composite (CVBS) and Y/C video signals as sample files, built in the time domain from the published analogue video standards — ITU-R BT.470/BT.1700, SMPTE 170M/244M and IEC 60856/60857.
It exists to produce known-good, reproducible test signals: material whose every sample you can predict, so that decoders, time base correctors and restoration tools can be exercised against a signal whose correct answer is already known. That includes laserdisc-style discs carrying VBI address codes, deliberately degraded signals with noise and dropouts, and multi-source "stacking" sets that model repeated captures of the same disc.
videosynth ships two front ends built from the same pipeline:
videosynth-gui— a Qt 6 desktop application for authoring projects, previewing frames and running generation.videosynth— the command-line generator, for scripted and batch use.
Both read and write the same YAML project file, and both produce byte-identical output from the same project.
What it can generate¶
- Standards-based signals for PAL, PAL-M, NTSC and SECAM, in composite or Y/C form, at 4fsc or raw high sample rates.
- Picture content from validated progressive sources — OpenEXR stills and MKV/MP4 video clips in any FFmpeg-decodable codec, colour-normalised to BT.601, optionally softened horizontally and vertically like a real camera and production chain (a measured Domesday preset).
- Vertical interval test signals (VITS) — the EBU, ITU, NTC-7, FCC and VIRS families.
- Laserdisc VBI metadata — IEC 60856/60857 24-bit biphase codes and NTSC 40-bit FM codes: picture numbers, programme time codes, chapters, picture stops, programme status, lead-in and lead-out.
- Impairments — two-component Gaussian noise with optional spectral shaping and a shared pressing layer, dropout simulation (random surface events and persistent scratches, flagged in a sidecar database or left unflagged), pressing channel effects (sub-sample timing offset, edge smear, PAL FM-beat herringbone), chroma gain and phase error, and a per-section luma bandwidth limit.
- Audio — up to eight stereo channel pairs at 48 kHz/24-bit, plus laserdisc EFM digital audio.
- On-screen display burn-in text with substitution tokens for picture number, timecode and frame number.
Where to start¶
- New to videosynth? Read Installation, then work through the Quick Start — it builds a complete PAL CAV laserdisc with VITS and IEC-compliant biphase metadata from scratch.
- Looking for what a particular feature does? The User Manual covers each subsystem in turn.
- Looking for the exact meaning of a YAML key? The Project File Reference documents the project file block by block.
Development status¶
videosynth is under active development, and some parts of the intended design are not yet implemented — VITC injection and custom per-line content in particular. This documentation describes the behaviour that is actually implemented; where something is planned but not yet available, it is called out explicitly.
If you spot a mistake, or would like to report an issue or contribute, please use the main repository:
videosynth is designed to be used alongside decoding and restoration tooling such as decode-orc and ld-decode.