spectrum draws spectrogram images beside selected catalogued music using FFmpeg with FlacCompagnon's filter and colour map. A spectrogram shows frequency content over time; a visual cutoff can inform an investigation but is not by itself proof that audio was transcoded.
Half-size images are the default; --size full uses the full drawing size. Existing pictures are skipped unless --full is supplied, including when only the size changed. --dry-run lists planned outputs without drawing, and --threads controls concurrent work.
The command creates sidecar images and needs write access to those folders; original music is read only. When tools/decoding fail, inspect the reported filename and verify format/tool availability before retrying. Use analyze for stored numerical measurements rather than interpreting an image as a checksum.
Rendering uses an isolated temporary output, then replaces the final picture only after success. Existing destination links and special files are refused before rendering and publication. A failed attempt preserves the previous picture; other selected tracks continue. Any picture failure makes the final command and its administrative server task fail, while keeping completed images.
Syntax and arguments#
aede spectrum [folder…]
Optional catalogued folders; no argument covers the catalog.
Options for this command#
| Option | Meaning |
|---|---|
--full | Redraw existing spectrograms, including when changing the requested size. |
--size VALUE | With fetch --covers: 250, 500, 1200 (default) or original. With spectrum: half (default) or full. |
--threads N | Number of worker threads. A positive integer fixes the count; 0 selects an automatic count. Plain copying defaults to one worker. |
--dry-run | Preview the work without making downloads or creating outputs. It can still validate tools and inputs. |
The shared options reference explains --data, --no-color, --help/-h, --version/-v/-V, option values and output/pagination rules. These shared presentation/data options do not make every command support CSV/JSON or pagination.
Examples#
aede spectrum "$HOME/Music/Jazz" --dry-run
aede spectrum "$HOME/Music/Jazz" --size full --full
Result and errors#
Output describes the selected operation or catalog data. Read any per-item warnings and retained-work summary; a completed process is not an independent integrity or audio-quality guarantee. Invalid command syntax/options normally exit with code 2; handler failures normally exit with code 1. Local interruption differs from a delegated server task, as explained in cancel.
Related reading#
Detailed existing guide: spectrograms.md.