TTY WAV Reader: Easy Playback for TeleTYpe Audio Files
What it is
- A TTY WAV reader is a tool that plays back and decodes WAV audio files containing Teletype (TTY/TDD) modem tones used for text-based telephone communication for Deaf and hard-of-hearing users.
Key features
- Tone decoding: Recognizes and decodes Baudot or 5-bit TTY tones (typically 45.45 or 50 baud).
- Audio input: Accepts WAV files from recordings, call logs, or direct captures.
- Playback control: Play, pause, seek, and adjust speed without corrupting decode.
- Filtering/cleaning: Noise reduction, bandpass filtering, and automatic gain to improve decoding accuracy.
- Export: Save decoded text as plain text or subtitle formats; optionally export timestamped transcripts.
- Real-time and batch modes: Decode single files interactively or process folders in bulk.
- Logging & diagnostics: Show signal quality, error rates, and raw bit/baud visualizations for troubleshooting.
Typical uses
- Accessibility: Replay and read TTY call recordings for users who need text output.
- Forensics: Recover textual content from recorded telephone lines.
- Development/testing: Validate TTY modem implementations or build assistive-communication tools.
- Archival: Preserve historical TTY exchanges in readable text.
Supported formats & protocols
- WAV PCM (mono/stereo, various sample rates) — best with 8 kHz or 44.1 kHz recordings.
- Baudot (ITA2) 5-bit encoding — standard for classic TTY.
- Some tools may support related protocols (e.g., V.21) or custom tone mappings.
How it works (high level)
- Preprocess audio: resample, normalize, and filter to target frequency bands.
- Detect tone presence and measure frequency/phase to separate MARK and SPACE.
- Demodulate into bitstreams using baud timing and synchronization.
- Group bits into 5-bit Baudot characters and apply shift states (LTRS/FIGS).
- Output decoded characters with timestamps and error indicators.
Accuracy tips
- Use recorded audio with minimal compression and high sample rate.
- Apply bandpass filters centered on TTY frequencies (~1400–1800 Hz depending on setup).
- Correct sampling-rate mismatches and remove DC offset before decoding.
- If many errors occur, try manual baud-rate adjustment or stronger noise reduction.
Example open-source tools
- FLAC/WAV + specialized scripts (Python with scipy/numpy) for custom decoding.
- Project-specific decoders and research tools on GitHub (search for “baudot decoder” or “tty decoder”).
When it may fail
- Highly compressed or lossy recordings, severe noise, or missing synchronization make decoding unreliable.
- Modern digital systems may use different signaling (e.g., real-time text over IP) that TTY decoders won’t handle.
If you want, I can:
- Recommend specific open-source TTY WAV reader projects on GitHub, or
- Provide a simple Python script example that decodes Baudot tones from a WAV file.
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