ARver

ARver is a command-line program for verifying audio tracks ripped from a CD against checksums stored in AccurateRip database.

The idea behind AccurateRip verification is that it's virtually impossible to get exact same errors when ripping different copies of the same CD on various CD drives. If the copies are scratched or otherwise degraded, read errors will occur in different disc sectors. CD drive defects are unlikely to manifest in the same way on different machines. Essentially, all read errors are expected to be unique, but in absence of errors only a single correct result exists.

AccurateRip database stores track checksums submitted by multiple users. When many users rip the same disc without errors, correct checksums are submitted to the database repeatably, boosting their "confidence" statistic. If a checksum of a ripped track is not found in the database, it indicates that the result is unique, meaning that disc read errors likely occurred while ripping.

ARver calculates the AccurateRip checksums of local files, fetches checksums for a given CD from the database, and displays a report which compares them.

Features

The package provides following command-line tools:

• arver: the main program. It determines the AccurateRip disc ID, fetches AccurateRip data, calculates checksums of ripped audio files, compares them with downloaded AccurateRip data and displays the result.

• arver-discinfo: displays disc IDs and the Table of Contents, fetches and displays all AccurateRip track checksums.

• arver-ripinfo: calculates checksums of audio files (ARv1, ARv2 and CRC32) and presents them as a table.

• arver-bin-parser: parses cached binary AccurateRip response and displays all AccurateRip track checksums.

Usage example

This example demonstrates the typical use case of arver: verification of files just ripped from a CD.

The tracks have been ripped using cdparanoia prior to running arver. AccurateRip disc ID is calculated based on the TOC of the CD which still is in the drive. arver fetches the checksums from the database, and compares checksums of local files with database entries.

In this case arver found that the third track was not ripped correctly, and reports a verification failure. The disc used for this example is affected by CD bronzing, and cdparanoia reported multiple issues toward the end of the last track.

Installation

For typical use:

python3 -m pip install arver

ARver requires Python 3.7 or newer. A pre-built wheel package is available on PyPI for CPython versions 3.7 and newer, targeting the x86_64 architecture for Linux. For other platforms installation is only supported from the source distribution (see the "Dependencies" section below).

While the wheel is forward-compatible with future 3.x Python versions, the latest Python releases may not have been tested. The latest tested Python version is listed in the PyPI trove classifiers.

For development:

git clone https://github.com/arcctgx/ARver
cd ARver
python3 -m pip install --editable .

For packaging:

git clone https://github.com/arcctgx/ARver
cd ARver
python3 setup.py install --root=/tmp/pkg-arver
# use contents of /tmp/pkg-arver to create a package.

Dependencies

ARver depends on following Python packages at runtime:

• discid
• musicbrainzngs
• pycdio
• requests

They will be installed automatically by pip install if needed. Alternatively, one can install them using provided requirements.txt file.

The source code includes a C extension which depends on libsndfile, so building from source requires a C compiler (gcc) and libsndfile headers. This makes libsndfile both compile-time and runtime dependency when ARver is installed from the source distribution.

Note about pycdio dependency

pycdio does not provide wheels, so if it's not already installed on your system, pip install arver will attempt to build it from source. Building from source may fail due to missing build-time dependencies. To work around this, you can try installing pycdio using your Linux distribution's package manager before installing ARver. If that doesn't work, you'll need to install the build-time dependencies listed on the pycdio GitHub page and then retry the installation with pip.

Restrictions

CD read offset corrections

Audio files must be corrected for CD drive read offset (e.g. by using -O option in cdparanoia). This is crucial for AccurateRip verification: without it the checksums of ripped tracks cannot be directly compared with database entries. ARver expects the input files to have zero offset, i.e. it assumes that required offset corrections were applied by the CD ripper. If this is not the case, all tracks will be reported as failing verification.

Hidden Track One Audio ("pregap track")

In some discs audio content is hidden in the pregap of track one. Many CD rippers (e.g. EAC or cdparanoia) can detect and rip it. Unfortunately, AccurateRip database does not store checksums of such tracks, so they can't be verified.

ARver will detect the presence of track one pregap, and will display it in CD TOC summary. If your ripper did extract the pregap track, do not pass its file name as argument to arver. It will change the track sequence and cause verification errors in other tracks. If you used a wildcard to specify audio files, use -x/--exclude option to ignore the pregap track.

Verifying Mixed Mode CDs

AccurateRip database does not store checksums of last audio tracks in Mixed Mode CDs. These tracks cannot be verified and their verification status will always show as N/A in the results summary.

Verifying Copy Controlled CDs

Copy Controlled CDs were designed specifically to prevent ripping. The way it is achieved makes these discs more sensitive to normal wear, and makes them not compliant with CD audio standard. Such CDs can often be ripped, but are much more likely to produce errors.

These CDs appear to arver and arver-discinfo as ordinary Enhanced CDs (multisession with data track in the end). It is not possible to distinguish them from normal Enhanced CDs based on the table of contents alone. If your disc bears "Copy Controlled CD" logo, verification problems are expected.

Verification without a physical disc

The regular use case of ARver is to verify a set of audio files right after they have been ripped, while the CD they have been ripped from is still in the drive.

Commands arver and arver-discinfo support an alternative mode of operation, where disc information is downloaded from MusicBrainz by disc ID lookup. While this can be useful, it is reliable only for Audio CDs. Information about data tracks is not encoded in MusicBrainz disc ID, but it is necessary to calculate AccurateRip disc ID. Attempts to verify discs with data tracks (Enhanced or Mixed Mode CDs) using disc ID lookup may not work at all, result in false negatives or low confidence values.

arver can try to guess the disc TOC based on the lengths of provided audio files with -t/--track-lengths option. This is considered expert usage: there is no way to know that files were ripped from a CD containing a pregap track or a data track, but it affects disc ID calculation. Options -D/--data-length and -P/--pregap-length can be used to provide this information if it is known from another source. Note that the lengths must be specified exactly: even an off-by-one mistake will result in a different (and probably wrong) disc ID.

If the data track length is provided, arver will calculate the disc ID as if it was an Enhanced CD. Verifying Mixed Mode CDs this way is not supported.

Acknowledgements

AccurateRip database is (c) Illustrate. Used with permission.

Thanks to the following people and projects for source code and inspiration:

• leo-bogert/accuraterip-checksum
• whipper-team/whipper
• cyanreg/cyanrip