SimpleSSTV

SimpleSSTV is a native iOS application for encoding and decoding slow-scan television (SSTV) signals; the method ham radio operators use to transmit images over audio frequencies.
Slow-scan television converts images to audio tones. Each pixel's brightness becomes a specific frequency between 1500-2300 Hz. Sync pulses at 1200 Hz mark line boundaries. The result is an audio signal you can transmit over any voice-capable radio, or record for later playback.
SSTV has been used by amateur radio operators since the 1950s to share images when bandwidth is limited. It's still actively used today on HF bands, VHF repeaters, and even for receiving images from the International Space Station.
-> ENCODING (Image to Audio)
• Load any PNG or JPG image via drag-and-drop or file picker
• Automatic resize and crop to SSTV resolution
• Choose from 14 supported modes covering all major SSTV formats
• Real-time encoding with progress visualization
• Play audio directly through speakers for VOX-triggered transmission
• Export to WAV file for later use
• Optional FSK ID callsign transmission (MMSSTV-compatible)
• Test pattern generator for signal testing
• Watermark with the app name in the first 16 scanlines. You can change or remove the watermark via a one-time In App Purchase
-> LIVE CAMERA MODE
• Real-time camera feed with front/back camera support
• Three trigger modes: Continuous, Motion-triggered, or Periodic interval
• Adjustable motion sensitivity for automatic capture
• Captures and encodes directly from camera to audio
• Perfect for portable operation and field events
-> DECODING (Audio to Image)
• Load WAV, M4A, or MP3 audio files containing SSTV signals
• Live microphone capture for real-time SSTV reception
• Automatic mode detection via VIS code identification
• Progressive line-by-line image preview during decode
• FSK callsign detection from received signals
• Handles real-world signal imperfections: timing drift, noise, sample rate variations
• Waterfall spectrogram display shows signal frequency over time
SUPPORTED MODES (14 total)
 
• Martin M1 (114s), Martin M2 (58s) - Popular in Europe
• Scottie S1 (110s), Scottie S2 (71s), Scottie DX (269s) - Popular in North America
• Robot 36 (36s), Robot 72 (72s) - Fast YCbCr modes
• PD50, PD90, PD120, PD160, PD180, PD240, PD290 - Pasokon Digital modes with superior color. Can be used to communicate with the ISS!

HISTORY MANAGEMENT
• Automatic saving of encoded and decoded images
• Collapsible history drawer with quick access to recent transmissions
• Filter by encoded or decoded images
• Reload previous images for re-encoding or review
TECHNICAL DETAILS
• Native Swift/SwiftUI means no Electron, no web views, no bloat
• DSP uses Apple's Accelerate framework for efficient FFT
• 44100 Hz sample rate for clean audio generation
• Phase-continuous tone generation for artifact-free signals
• Robust decoder handles truncated files, timing drift, and various sample rates
PRIVACY
SimpleSSTV operates entirely offline on your device. No accounts, no cloud sync, no analytics, no data collection. Your images and audio files stay on your device. Please note that encoded images are NOT encrypted in any way, and can be freely decoded by anyone receiving the audio!
REQUIREMENTS
• iOS 18 or later
• Camera access required for live mode
• Microphone access required for live decode
• File access for loading images and saving WAV files
This simple, no nonsense utility was built by a ham radio operator for ham radio operators. 73!