SSTV Generator

Purpose & User Intent: The tool encodes a user-supplied image into a radio-grade SSTV audio signal for amateur radio operations. Users are ham radio operators, SSTV hobbyists, educators, and clubs who need repeatable, standards-compliant audio for transmission tests, field demos, or archival purposes. When to use: prior to a planned transmission, during practice sessions, or for creating demonstration material.
Core Logic & Features: The system performs image-to-SSTV frame encoding using a selected mode (Scottie 2, Martin M1, PD, etc.). Required features: input image, mode, and output generation. Optional/advanced: adjustable sample rate, output format (WAV/MP3), cropping/resizing, aspect-ratio handling, and metadata tagging. Behavior: color space conversion, line timing, color burst generation, and mode-specific header data. Output is an audio file that can be fed into a decoder or transmitter chain.
Inputs & Outputs: Inputs: image_file (required; PNG/JPG; max size 10 MB), mode (required; one of: PD, Scottie 2, Martin M1), sample_rate (optional; Hz; default 48000), output_format (optional; WAV or MP3). Outputs: sstv_audio_file (audio file; format matches output_format; duration depends on image and mode), metadata: duration_seconds, bitrate.
Algorithms & Calculations: The encoding implements the standard SSTV frame structure: scanline timing, color-to-frequency mapping per mode, and line-sync/guard-tone sequences. The algorithm converts image pixels to color values, maps to the appropriate color codes, assembles frames, and encodes into an audio waveform. It adheres to documented timing and spectral characteristics of SSTV.
Error & Edge Cases: Invalid or unsupported image formats, oversized input, or missing required inputs raise explicit errors. If the selected mode is not recognized, a safe default is used. Large files may be resized; if audio encoding fails, the tool returns a lossless WAV fallback.
Industry/Region & Localization: Aligns with international SSTV standards from amateur radio organizations; uses SI units for sample rates and durations; locale affects only textual metadata.
Assumptions & Exclusions: Assumes input image is a still image; does not perform real-time streaming or video-to-SSTV; not responsible for RF transmission or legal permissions.