CopyOfA

CopyOfA is a preservation and forensic toolkit for music collectors. It acquires and maintains trustworthy evidence of recorded audio, then lets collectors analyze, compare, and share what that evidence reveals.

Status

The project is restarting from a clean slate. Its first release, v0.1.0, preserves a selected file delivery as an Evidence Set and verifies it later. The second, v0.2.0, describes the audio in a set: each track's format and properties, an Audio Digest for lossless audio, and a few measurements. The third, v0.3.0, measures how two preserved tracks relate, across formats and sample rates. The fourth, v0.4.0, shares a comparison: a Report can leave out where the Evidence Sets are stored, view turns it into a self-contained HTML page, and validate checks any Report against its published JSON Schema. The fifth, v0.5.0, preserves a plain audio CD: acquire reads it with redumper into an Evidence Set that stores the disc image compressed, inspect and compare read its tracks from the image, and export writes them as FLAC files. The sixth, v0.6.0, locates matching portions: compare reports which portions of one track appear in the other, where and how alike, and which audio appears in only one. The roadmap in the Product Map lists what comes next.

The previous implementation, which archived optical discs bit-exactly with redumper, is retired. Its last code change is commit 0d04a38 in the Git history. It does not define the new architecture or release sequence.

Installation

CopyOfA runs on macOS and Linux with Python 3.11 or later. Install it from PyPI with uv:

uv tool install copyofa

Usage

Preserve files you already own, such as a download purchase, as a new Evidence Set:

copyofa import ~/Downloads/Album --to /Volumes/Archive/Album \
  --note "Bandcamp purchase" --ref discogs=r123456

• Each source, a file or a directory, goes into the set under its base name.
• --to names a directory that must not exist yet; the set appears there only once every stored copy has been checked against its source.
• --exclude <pattern> leaves out files and directories by shell-style pattern; operating system metadata files such as .DS_Store, symbolic links, and empty directories are left out too. Every exclusion is recorded with its reason.
• --note and --ref record provenance exactly as given; --ref repeats.
• --json prints the result as JSON. Progress and errors go to stderr.

The command exits 0 when the set is accepted, 1 when the import is refused or fails, 2 for invalid arguments, and 130 when canceled with Ctrl-C. Evidence Set format describes the set and how to check it without CopyOfA.

Preserve a plain audio CD by reading it with redumper, build b768 or later, installed separately:

copyofa acquire --to /Volumes/Archive/add-violence-cd --note "Bought new"
copyofa acquire --to /Volumes/Archive/add-violence-cd --drive disk6 --json \
  > acquisition.json

• Acquire runs redumper disc once and keeps everything it wrote but the track files, which the disc image reproduces: the image as FLAC, the read status and the subchannel as xz, and the small files as written. Each compressed file is decoded and checked against redumper's original before the set is accepted.
• The set's Acquisition Record gives the drive, the redumper build, the offsets, the read errors, and each track's range in the image and Audio Digest.
• --drive names the drive as redumper does, such as disk6; without it, redumper reads the first drive holding a disc. --note, --ref and --json work as for import.
• A disc with more than one session or with a data track is refused.

Acquire exits 0 when the set is accepted from a disc read without error, 1 when it is accepted from a disc read with errors (the set is kept, as evidence of what the drive read) or the acquisition is refused or fails, 2 for invalid arguments, and 130 when canceled. Evidence Set format describes acquired sets and how to restore redumper's files with flac and xz.

Later, after moving the set or just to check it, verify it against its Integrity Baseline:

copyofa verify /Volumes/Archive/Album
copyofa verify /Volumes/Archive/Album --json > album-verification.json

Verify reads every preserved file and reports each one as matching, changed, missing, unavailable, or not checked, and lists unexpected files under data/. Operating system metadata files that Finder adds while browsing the set are ignored. It writes nothing into the set. --json prints a verification Report, which Verification Report format describes.

Verify exits 0 when everything is intact, 1 when it found anything else, 2 when the target is not an Evidence Set or the arguments are invalid, and 130 when canceled.

Describe the audio the set holds:

copyofa inspect /Volumes/Archive/Album
copyofa inspect /Volumes/Archive/Album --json > album-inspection.json

Inspect first checks each preserved file against the Integrity Baseline, then decodes FLAC (8, 16 or 24 bits), integer PCM WAV and MP3, and reports each track's format, sample rate, bit depth, channels and duration. Other files are reported as not interpreted, with the reason. --json prints an inspection Report, which Inspection Report format describes. For FLAC and WAV it gives an Audio Digest, which recognizes the same audio after retagging or recompression and can be reproduced with flac or ffmpeg. MP3 has none, because its decoded samples depend on the decoder. The Report also gives each track's peak per channel and its digital silence at each end, and for FLAC whether the audio matches the MD5 signature its encoder stored.

For a set made by acquire, inspect also decodes each track of the disc from the image, over the range the Acquisition Record gives, and reports whether its Audio Digest is the one recorded at acquisition.

Inspect exits 0 when every file was decoded or is not a supported format, 1 when a file could not be inspected or decoded or its audio differs from its FLAC MD5 signature, or when a track of an acquired set could not be decoded or differs from its recorded Audio Digest, 2 when the target is not an Evidence Set or the arguments are invalid, and 130 when canceled. It writes nothing into the set.

Find which portions of one preserved track appear in another, such as a FLAC track and the MP3 of the same song from another release:

copyofa compare "/Volumes/Archive/With Teeth/data/04 The Hand That Feeds.flac" \
  "/Volumes/Archive/Definitive NIN/data/18 The Hand That Feeds.mp3"
copyofa compare <input-a> <input-b> --json > comparison.json
copyofa compare <input-a> <input-b> --json --omit-locations > shareable.json

Each input is a file under the data/ directory of an Evidence Set. To compare a track of a disc you acquired, give the acquired set and the track number with --track-a or --track-b:

copyofa compare "/Volumes/Archive/Add Violence CD" \
  "/Volumes/Archive/Add Violence/data/01-04 Not Anymore.flac" --track-a 4

Track A: track 4 of /Volumes/Archive/Add Violence CD (flac, 44100 Hz, 16-bit, 2 channels, 3:06.733)
Track B: /Volumes/Archive/Add Violence/data/01-04 Not Anymore.flac (flac, 48000 Hz, 24-bit, 2 channels, 3:11.600)
Common sample rate: 44100 Hz
Portion 1, primary: A 4.098-186.720 s, B 4.891-187.513 s, offset +34946 frames (+0.792 s), correlation 0.997, residual (one gain) -22.0 dB
Portion 2, primary: A 8.548-16.714 s, B 17.912-26.078 s, offset +412945 frames (+9.364 s), correlation 0.996, residual (one gain) -21.3 dB
Portion 3, primary: A 17.119-25.294 s, B 9.340-17.515 s, offset -343054 frames (-7.779 s), correlation 0.997, residual (one gain) -22.5 dB
Portion 4, alternate: A 22.365-24.129 s, B 40.300-42.064 s, offset +790945 frames (+17.935 s), correlation 0.983, residual (one gain) -14.8 dB
Portion 5, alternate: A 39.493-41.272 s, B 23.142-24.921 s, offset -721054 frames (-16.350 s), correlation 0.984, residual (one gain) -15.0 dB
Portion 6, alternate: A 66.289-67.779 s, B 112.819-114.309 s, offset +2051978 frames (+46.530 s), correlation 0.958, residual (one gain) -10.8 dB
Portion 7, alternate: A 111.994-113.517 s, B 67.049-68.572 s, offset -1982087 frames (-44.945 s), correlation 0.959, residual (one gain) -11.0 dB
Unmatched in A: 0.000-4.098 s, -36.8 dBFS
Unmatched in A: 186.720-186.733 s, -11.8 dBFS
Unmatched in B: 0.000-4.891 s, -31.1 dBFS
Unmatched in B: 187.513-191.600 s, -20.8 dBFS

Compare checks both against their Integrity Baselines and decodes them as inspect does. It then resamples the one at the higher sample rate to the lower rate and searches for the portions of track A that appear in track B, each at its own offset. For each portion it reports its range in both tracks, its offset, and how B relates to A over it: correlation, gain and the residual level left after that gain. It also reports the audio that no primary portion covers, with its level. In the example, portion 1 covers nearly all of the CD track, and B starts 0.792 s later. Portions 2 and 3 match other places of B for sections of A that portion 1 also covers; the alternates match sections that better portions already cover, less well. The first 4.1 s of A, and the first 4.9 s and the last 4.1 s of B, match nothing. When both tracks are lossless and their Audio Digests are equal, compare reports identical audio. It draws no conclusion such as "same master". --json prints a comparison Report, which Comparison Report format describes, with the method's parameters. To share a Report, add --omit-locations: it leaves out where each Evidence Set is stored, which names your disks and often your user account, and the Report says that it did.

Compare exits 0 when both tracks were compared, whether or not it found a portion, 1 when a track could not be inspected or decoded or is not a supported format, 2 when an input is not inside an Evidence Set or the arguments are invalid, and 130 when canceled. It writes nothing into either set.

Play a disc you acquired, or tag its tracks with other tools, from FLAC files that export writes:

copyofa export "/Volumes/Archive/Add Violence CD" --to ~/Music/add-violence
copyofa export "/Volumes/Archive/Add Violence CD" --to ~/Music/add-violence --json \
  > export.json

Export checks the set as inspect does, then writes each track of the disc from the image as a 16-bit stereo FLAC file at 44.1 kHz, 01.flac, 02.flac and so on, with no tag. It decodes each file and checks its Audio Digest against the recorded one before it accepts the directory. The first track's pregap, the lead-in and the lead-out stay only in the set. --json prints an export result, which Export result format describes.

Export exits 0 when every track was exported, 1 when the set is not an acquired set, cannot be trusted, or the export is refused or fails (the directory is then not created), 2 when the target is not an Evidence Set or the arguments are invalid, and 130 when canceled. It writes nothing into the set.

Check that a Report, such as one you received, is well formed:

copyofa validate comparison.json
copyofa validate comparison.json --json > comparison-validation.json

Validate parses the file as strict JSON, then checks it against the JSON Schema published for its Report kind and format version, and reports valid, invalid with the location of each problem, or unsupported for a kind or version it does not know. A valid Report is well formed, nothing more: validation does not establish that its findings are true, who produced it, or anything about the audio. The schemas ship in the package, so other software can check a Report without CopyOfA. --json prints a validation result, which Validation result format describes.

Validate exits 0 when the Report is valid, 1 when it is invalid or unsupported or the file cannot be read, 2 when the arguments are invalid, and 130 when canceled. It writes nothing.

Read a comparison Report as a web page, without CopyOfA:

copyofa view comparison.json > comparison.html

View validates the file first, then prints one HTML page that shows every value of the Report with labels and units, each absent value with its reason, and each limitation. It gives the SHA-256 of the Report file it was generated from, so a recipient can check the page against the Report. The page runs no script and loads nothing, so it opens in any browser, offline. It draws no conclusion from the measurements. For a Report of the current format, it shows the method's parameters, a table of the portions with each one's residual windows, and the unmatched audio of each track. Comparison Report format describes it.

View exits 0 when it printed the page, 1 when the Report is invalid, unsupported, not a comparison Report, or cannot be read, 2 when the arguments are invalid, and 130 when canceled. It prints nothing on stdout otherwise, and writes no file.

Documents

• Manifesto: vision, target users, principles and non-goals.
• Product Map: capabilities, collector scenarios, core concepts, and the Now / Next / Later roadmap.
• Briefs: the scope and acceptance criteria of planned work.
• Decisions: architecture decision records.
• Formats: the files CopyOfA writes.

GitHub release milestones and their issues will hold the committed work.

Development

With uv and just installed:

just setup  # Install dependencies and git hooks
just qa     # Run all checks
just test   # Run the tests

CONTRIBUTING.md covers the development setup, pull requests and releases; AGENTS.md holds the commands and conventions for contributors and coding agents.

License

CopyOfA is licensed under the Apache License 2.0.