Spektra

A desktop audio spectrum analyzer: drop in an audio file, see its spectrogram, compare encodes side by side, and get an automated "is this really lossless?" verdict.

Features

• Progressive spectrogram with time/frequency rulers and dB legend
• Automated bandwidth verdict: detects a lossy low-pass cutoff and reports Lossless / Suspicious / Lossy with a likely codec/bitrate guess
• Upsampling detection: a hi-res file whose real bandwidth stops at a lower standard rate (a 96 kHz container holding 22.05 kHz of content) is flagged Upsampled, naming the likely true source rate
• Export report: save the bandwidth + integrity audit for the current file or a whole folder as CSV/JSON (File → Export Report… / Export Folder Report…)
• Zoom & pan: wheel = time zoom, Shift+wheel = frequency zoom, drag = pan, double-click = reset (zoomed spans re-render sharply via ffmpeg segment decode)
• Cursor readout (time, frequency, dB) and a toggleable average-spectrum overlay (peak-hold + time-average)
• Preferences: FFT size, window function (Hann/Hamming/Blackman/Blackman-Harris), color palette (Magma/Viridis/Inferno/Grayscale), dynamic-range floor, and a linear or logarithmic frequency axis
• Save the spectrogram to PNG (Ctrl+S) or copy it to the clipboard (Ctrl+Shift+C)
• Tabs: open many files at once (dialog, drag-drop, or CLI args)
• Per-channel or mixdown analysis for multichannel files
• Recent files + window placement remembered across runs
• Compare two files: stacked spectrograms on a shared time axis, synced zoom/pan, manual + automatic (cross-correlation) time alignment, A/B flip, and a signed A−B difference view (diverging colormap) with a numeric diff score
• Null test (time-domain A−B residual) and drift detection for misaligned encodes
• Integrity check: flags corrupt frames, missing data (interior digital silence), and truncated (partially downloaded) files, in the app (Ctrl+I) or the CLI
• Loudness & dynamics: integrated LUFS, loudness range, true peak, crest factor, and a clipping hint (EBU R128 via ffmpeg), in the app (Ctrl+L) or the CLI

Keyboard shortcuts

Shortcut	Action
Ctrl+O	Open audio files
Ctrl+W · Ctrl+Tab	Close tab · switch tabs (Shift to reverse)
Ctrl+S · Ctrl+Shift+C	Save the spectrogram to PNG · copy it to the clipboard
Ctrl+E · Ctrl+R	Preferences · toggle the average-spectrum overlay
Ctrl+I · Ctrl+L	Check integrity · measure loudness (LUFS)
Wheel · Shift+Wheel	Zoom time · zoom frequency
Drag · Double-click	Pan · reset the view
T · D · A · Esc	Compare view: flip A/B · difference · auto-align · back to both
Ctrl+D · Ctrl+Shift+S	Compare two files · export the current file's report
Ctrl+0 · Ctrl+1..Ctrl+9	Reset the view · jump to tab N
Ctrl+Up / Ctrl+Down · F5	Previous / next channel · reload the file
Ctrl+H	Toggle the crosshair (cursor line + readout)

Check for a newer release any time from Help → Check for Updates. Spektra never updates itself; it only tells you when a newer release exists and links to it. You can also enable a quiet once-a-day check on startup in Preferences.

Documentation

• GUI guide: inspecting files, verdict banners, compare workflows, integrity/loudness checks, report export.
• CLI guide: every command with sample output, JSON/CSV reports, exit codes, and scripting examples.

Download

Grab the latest build from the releases page:

• Spektra-<version>-Setup.msi: the Windows installer for the desktop app (can add spektra to your PATH).
• Spektra-<version>-win-x64.zip: the portable desktop app, no install needed.
• spektra-cli-<version>-<os>.zip: the command-line tool (Windows, Linux, macOS).

Spektra isn't code-signed yet, so Windows SmartScreen may show "Windows protected your PC" or an Unknown Publisher prompt. That's expected for an unsigned open-source build, not a sign of a problem: choose More info → Run anyway to continue. To verify a download first, check it against the SHA256SUMS.txt published with each release:

# Windows (PowerShell)
(Get-FileHash .\Spektra-<version>-Setup.msi -Algorithm SHA256).Hash

# Linux / macOS
sha256sum -c SHA256SUMS.txt

Requirements

• Windows (primary target; Avalonia keeps Linux/macOS possible)
• ffmpeg + ffprobe, found via the app folder, %LOCALAPPDATA%\Spektra\ffmpeg, or PATH. If missing, Spektra offers a one-click download. ffmpeg is invoked as a separate process and is not linked or bundled.

Build & run

dotnet run --project src/Spektra.App -- <optional-audio-file>

Compare two files directly (also available in-app via File → Compare…):

dotnet run --project src/Spektra.App -- --compare <fileA> <fileB> [--auto] [--mode diff]

Command line

Spektra ships a small cross-platform companion CLI (spektra) that reuses the analysis engine. It writes to stdout and exits 1 when anything looks lossy or corrupt:

spektra report <file|folder> ...   Bandwidth verdict per file.
spektra scan <folder>              Compact bandwidth scan of a library.
spektra check <file|folder> ...    Integrity check (corruption / missing data).
spektra audit <file|folder> ...    Bandwidth + integrity together.
spektra loudness <file|folder> ... Loudness (LUFS), true peak, and dynamics.

Add --json or --csv to any command for a machine-readable report:

spektra scan Music --csv > library.csv

Full command reference with sample output and scripting recipes: docs/cli.md.

(--report / --scan are accepted too.) Build it with dotnet publish src/Spektra.Cli -c Release.

Test

dotnet test

License

PolyForm Perimeter 1.0.1. © Rares (rarepops).