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Boof2015
315 lines
16 KiB
Markdown
315 lines
16 KiB
Markdown
<div align="center">
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<img src="assets/prism-badge.png" alt="Prism" width="440">
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**Real-time audio analysis and metering, wherever you work.**
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</div>
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Prism is a free, open-source audio analyzer and meter rack for Windows, macOS, and Linux.
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Monitor system audio or an input with a configurable set of real-time scopes and meters, arrange them however you like, and save the setup as a profile. The same analyzers are also available as VST3/AU plugins, and Prism includes a native terminal interface for lightweight monitoring.
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## Scopes
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Prism includes seven real-time scopes and meters:
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* **Spectrum Analyzer** — FFT spectrum with calibrated dBFS levels, configurable FFT size, spectral tilt, Log/Mel/Linear scales, heatmap and fill modes, and peak/pitch readouts
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* **Oscilloscope** — Time-domain waveform with fundamental-frequency pitch locking and sub-sample triggering for a stable display
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* **Vectorscope** — Full-band stereo phase analysis with XY, Polar, and M/S Linear views, calibrated references, adjustable zoom, and optional multiband RGB
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* **Spectrogram** — Scrolling frequency-over-time display with Log/Mel/Linear scales, stereo-energy analysis, and frequency reassignment in Sharp and Sharper modes
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* **VU Meter** — 300 ms metering with adjustable 0 VU reference, stereo correlation, and needle or bar displays
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* **Loudness Meter** — ITU-R BS.1770 momentary, short-term, and integrated LUFS metering with BS.1770 true-peak activity
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* **Waveform** — Scrolling mono or stereo waveform with transient-preserving min/max sampling and optional multiband energy visualization
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Every scope can be configured independently. Resize and rearrange them into a rack, rotate supported scopes, pop them into separate windows, or pin them on top of other applications.
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Spectrum, Spectrogram, Oscilloscope, and Waveform also include interactive measurement overlays for inspecting frequency, level, pitch, amplitude, or time directly from the display.
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<details> <summary><strong>Stats for nerds</strong></summary>
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Most of Prism's analysis runs in native C++, with the same DSP implementations reused across the desktop app, DAW plugins, and terminal interface where applicable.
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### Spectrum
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* Hann-windowed FFT with selectable sizes from 1024 to 16384 samples
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* Coherent-gain correction for calibrated dBFS magnitude rather than arbitrary FFT amplitude
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* Native calibration tests measure bin-centered tones within ±0.05 dB and off-bin interpolated peaks within 0.3 dB across all exposed FFT sizes
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* Maintains Mid, Side, Left, Right, and channel-max spectra internally
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* Logarithmic, Slaney Mel, and Linear frequency scales
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* Extended 10 Hz–24 kHz and Audible 20 Hz–20 kHz ranges, automatically clamped to Nyquist
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* Independent spectral and heatmap tilt around a 1 kHz reference
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* Peak analysis can report dBFS, frequency, musical note, octave, and cents offset
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* Interactive measurement overlay exposes frequency, level, and pitch directly from the graph
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### Spectrogram
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* Hann-windowed FFT with 4× zero-padding
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* Coherent amplitude normalization for calibrated spectral levels
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* Native tests keep tone levels within 0.3 dB across multiple FFT sizes, amplitudes, and off-bin frequencies
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* Logarithmic, Slaney Mel, and Linear frequency mapping
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* Frequency placement is tested across 44.1, 48, and 96 kHz sample rates
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* Classic mode provides a conventional spectral display
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* Focused mode relocates local spectral peaks using phase correction and a local spectral centroid
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* Sharp and Sharper perform phase-based frequency reassignment rather than post-process image sharpening
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* Reassignment operates on every visible contributing FFT bin instead of only local maxima, preserving quieter partials and ambience
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* Reassigned power compensates for Hann-window equivalent noise bandwidth and zero-padding so relocation remains level-calibrated
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* Stereo analysis combines L/R energy rather than summing to mono, so anti-phase material remains visible instead of cancelling out
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* Native tests verify reassigned tones stay on the correct Log, Mel, and Linear frequency rows
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* Interactive inspection reports frequency, pitch, and time history
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### Oscilloscope
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* FFT-based fundamental detection over a 2048-sample analysis window
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* Pitch detector currently searches from 40 to 1000 Hz
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* Pitch-lock dynamically retunes a narrow FIR band-pass around the detected fundamental
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* Triggering follows a rising zero crossing rather than simply drawing the newest block of samples
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* Trigger positions retain sub-sample precision
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* Catmull-Rom interpolation is used when reading the waveform at fractional sample positions
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* Adaptive pitch smoothing locks quickly at startup and becomes more conservative once stable
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* Interactive measurement reports time, linear amplitude, and dBFS
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### Vectorscope
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* Full-band L/R analysis with no hidden high-frequency low-pass
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* Native regression tests explicitly verify preservation of content above 8 kHz at 44.1, 48, and 96 kHz
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* XY mode uses the original channel samples directly: Right on X, Left on Y
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* XY and M/S Linear modes use calibrated channel-amplitude reference boundaries
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* Polar retains an intentionally amplitude-compressed radial projection so low-level stereo structure remains readable
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* Folded modes rotate negative-Mid samples rather than discarding them
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* Adjustable display zoom from −12 to +24 dB without modifying the underlying signal
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* Optional three-band stereo view with 250 Hz and 2.5 kHz crossovers
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* Multiband analysis retains separate low, mid, and high L/R signals
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### Loudness
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* ITU-R BS.1770-style K-weighting using the pre-filter and RLB weighting stages
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* Momentary loudness uses a 400 ms window
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* Short-term loudness uses a 3 second window
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* Integrated loudness uses overlapping 400 ms blocks with 100 ms hops
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* −70 LUFS absolute gate
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* Relative gate at −10 LU below ungated programme loudness
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* Momentary, short-term, and integrated LUFS are calculated independently
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* Stereo true-peak reconstruction uses a rate-aware 48-tap-per-phase FIR at 2× to 8× oversampling for common 44.1–192 kHz host rates
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* Held L/R true-peak markers and a reset-scoped combined maximum are reported in dBTP
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### VU and correlation
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* 300 ms RMS integration window
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* Adjustable 0 VU calibration from −30 to 0 dBFS
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* Default reference is 0 VU = −14 dBFS
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* Stereo correlation is calculated over the same analysis window and reported from −1 to +1
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* 750 ms sample-peak hold
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* Peak decay of 18 dB/s
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* Bar envelope uses a 5 ms attack and 180 ms release
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* Needle and bar displays can use the same underlying analysis
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### Waveform
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* Each rendered time column retains the minimum and maximum sample instead of selecting or averaging a single sample, helping preserve short transients while downsampling the history
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* Mono and separate stereo-lane modes
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* Optional multiband view calculates low, mid, and high RMS energy for every displayed time column
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* Uses the same 250 Hz and 2.5 kHz multiband split as the vectorscope
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* Interactive measurement reports time history, amplitude, and dBFS
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### Capture
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* Native CoreAudio system-output capture on macOS using Audio Hardware Taps
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* Native WASAPI loopback capture on Windows
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* Native PulseAudio monitor-source capture on Linux
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* Linux capture handles U8, 16-bit, 24-bit, 32-bit integer, and 32-bit floating-point PulseAudio formats before normalizing them for analysis
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* Microphone and interface inputs use a separate low-latency AudioWorklet capture path
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* Capture follows the active device sample rate instead of assuming a fixed 44.1 or 48 kHz analysis rate
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### Rolling capture
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* Keeps the previous 5, 10, 30, or 60 seconds of audio available without starting a recording beforehand
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* Buffer is stored as PCM and exported as a standard RIFF/WAV file
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* Mono and stereo capture are supported
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* Exported clips use 16-bit PCM
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* The export path supports source sample rates up to 384 kHz
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* Captured audio can be dragged directly out of Prism as a file
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### DAW plugins
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* All seven Prism analyzers are built from the same native DSP source used by the desktop application
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* VST3 on Windows, macOS, and Linux
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* AU on macOS
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* Mono and stereo host layouts are supported
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* Analyzer plugins are pure pass-through: Prism does not modify the host's audio buffer
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* The realtime process callback only copies samples into a FIFO
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* FFT, loudness, visualization, and other analysis work happens outside the realtime audio thread
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* Scope configuration is serialized into the DAW's project/plugin state
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* Plugins use JUCE 8 and a shared Prism web UI while keeping analysis native
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### Terminal UI
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* Native C++ frontend using the same Spectrum, Oscilloscope, Vectorscope, VU, Loudness, Spectrogram, Waveform, and system-capture implementations
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* 60 FPS default rendering
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* Experimental 120 FPS mode
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* Compatibility mode uses 256-color output at up to 60 FPS
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* Safe mode uses basic ANSI colors and caps rendering at 30 FPS
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* Supports live output-device switching
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* Supports input trim before every analyzer
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* Includes pitch locking, vectorscope modes, calibrated VU reference levels, spectrogram reassignment modes, mono/stereo waveform views, and multiband analysis
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* Reads Prism .iro themes and has its own shareable profile/customization system
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* Typically uses around 35 MB of RAM
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### Rendering and measurement
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* Desktop visualizers can target 10, 30, 60, 120, or 144 FPS, or synchronize to the display refresh rate
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* Spectrum, Spectrogram, Oscilloscope, and Waveform support interactive measurement overlays
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* Measurement coordinates account for scope rotation and mirroring, so displayed readouts continue to correspond to the underlying signal after transforming a scope
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</details>
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## Desktop
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Prism can capture system output directly through CoreAudio on macOS, WASAPI on Windows, and PulseAudio on Linux. It can also switch to an input device when you want to analyze a microphone, interface, or line input.
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No virtual audio cable is required for normal system capture.
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The main rack and scope popouts can use solid, blurred, or clear backgrounds, making Prism usable as a normal desktop application or as a set of unobtrusive overlays.
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Prism can also live in the system tray, start automatically with your computer, and launch either normally or out of the way when you want it running all the time.
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## Rolling Capture
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Prism can continuously keep the last **5, 10, 30, or 60 seconds** of audio in memory.
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When you hear something you want to keep, drag the buffered audio out of Prism as a WAV file. There is no need to start recording beforehand.
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## DAW Plugins
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Every Prism scope is also available as a DAW plugin.
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Drop a **Spectrum**, **Oscilloscope**, **Vectorscope**, **Spectrogram**, **VU Meter**, **Loudness Meter**, or **Waveform** onto a track and analyze it using the same interface and analysis engine as the desktop app.
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* **VST3** on Windows, macOS, and Linux
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* **AU** on macOS
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* Settings are stored with your project
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* Plugins follow your Prism themes and profiles
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* Audio passes through untouched
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Tested in Ableton Live, FL Studio, and Reaper.
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The plugins install alongside Prism, so there is no separate download.
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## Terminal UI
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Prism also includes `prism-tui`, a native terminal interface built on the same capture and analysis code.
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It provides real-time spectrum, metering, loudness, and other monitoring tools without needing to run the desktop interface.
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`prism-tui` is lightweight, typically using around 35 MB of RAM.
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```bash
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prism-tui
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prism-tui --list-outputs
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prism-tui --output <id>
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prism-tui --profile <name>
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prism-tui --theme <name>
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prism-tui --help
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```
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Profiles and `.iro` themes can be used from the TUI as well, and output devices can be changed without leaving it.
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`prism-tui --help` lists the available controls and launch options.
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## Profiles
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A profile stores your Prism workspace: which scopes are visible, how they are laid out, their individual settings, and window state.
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Keep different profiles for different setups or workflows and switch between them when needed.
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Profiles are stored as `.prsm` files and can be shared with other Prism users.
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## Themes
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Prism's interface is themeable through editable `.iro` files.
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Themes control the colors used throughout the application and its scopes. You can edit your own, drop them into the `Prism Themes` folder, or download themes made by the community.
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Prism also includes chroma-key-friendly themes for using scopes as overlays in OBS or other video software.
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## Download
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Prebuilt versions of Prism for Windows, macOS, and Linux are available on the [Releases](https://github.com/Boof2015/prism/releases) page.
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Installable packages include the desktop application and the components supported by that package, including DAW plugins and `prism-tui` where applicable.
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On Windows, the NSIS installer adds `prism-tui` to the machine `PATH`. Open a new terminal after installation so it inherits the updated environment. The portable Windows package does not modify `PATH`.
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## Building from Source
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**Prerequisites:** Node.js 18+, npm, CMake 3.22+, and a C++ compiler toolchain.
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| Platform | Toolchain |
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| -------- | ------------------------------------------------------------------------------------------------------- |
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| macOS | Xcode Command Line Tools |
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| Windows | Visual Studio Build Tools |
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| Linux | `build-essential`, `python3`, `libasound2-dev`, `libpulse-dev`, `libgtk-3-dev`, `libwebkit2gtk-4.1-dev` |
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```bash
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git clone https://github.com/Boof2015/prism.git
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cd prism
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npm install
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```
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The `postinstall` script compiles the native C++ module for your platform.
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```bash
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npm run dev # Development
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npm run build # Build application assets
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npm run configure:tui # Configure the standalone CMake project
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npm run build:tui # Build prism-tui
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npm run test:tui # Build and run native TUI tests
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npm run test:lufsmeter-native # Run generated BS.1770/EBU true-peak vectors
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npm run dist # Package for current platform
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npm run dist:mac # macOS
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npm run dist:win # Windows
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npm run dist:linux # Linux
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```
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If you have downloaded and extracted the official [EBU Loudness Test Set](https://tech.ebu.ch/publications/ebu_loudness_test_set) for internal testing, run cases 15–23 without copying the WAVs into the repository. The files are not downloaded or redistributed by Prism, in accordance with the [EBU test-sequence usage terms](https://tech.ebu.ch/files/live/sites/tech/files/shared/testmaterial/use%20of%20EBU%20AUDIO%20test%20sequences.pdf).
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```bash
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npm run test:lufsmeter-ebu -- /path/to/extracted-ebu-loudness-test-set
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```
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The TUI build downloads the pinned FTXUI source through CMake. Linux also requires the PulseAudio development package.
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The DAW plugins build with CMake from the [`plugin/`](plugin/) directory. See [`plugin/README.md`](plugin/README.md) for per-platform build and installation details.
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## Astra Integration
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Prism can optionally connect to [Astra](https://github.com/Boof2015/astra) through its local API to show currently playing music, cover art, track information, and playback controls alongside your scopes.
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Prism does not require Astra and works as a standalone application.
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## Support
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If you find Prism useful and want to support a broke college student, consider supporting development:
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[](https://ko-fi.com/boof2015)
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## License
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Prism is licensed under the [GNU General Public License v3.0](https://www.gnu.org/licenses/gpl-3.0.html). See [LICENSE](LICENSE) for the full text.
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Third-party license notices are recorded in [THIRD_PARTY_NOTICES.md](THIRD_PARTY_NOTICES.md).
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