ADC File

What are ADC files and how to open them

Are you having problems opening an ADC file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your ADC files.

What is an ADC file?

ADC files have multiple uses, and Adaptive Differential Coding Audio is one of them. Read more about the other uses further down the page.

Adaptive Differential Coding Audio

Adaptive Differential Coding Audio is a lossy audio compression format designed by Nania Francesco. It compresses digital audio by predicting future samples in the time domain, coding the error (difference) rather than transforming into frequency spectra. It aims to provide higher perceptual fidelity than MP3 or AAC at comparable bitrates, especially for sustaining clarity and dynamics.

Files in this format are created by the ADC encoder software, which reads standard uncompressed PCM audio (usually 16-bit or 24-bit, mono or stereo), applies subband filtering, uses adaptive prediction and quantization per band, then encodes the result using binary arithmetic coding. Decoding reverses these steps to reconstruct the waveform-approximation audio. Commonly used in recent versions (e.g. v0.82), ADC works with 8 subbands, supports joint stereo or mid/side modes, and operates in bitrates comparable to or better than existing lossy codecs in listening tests.

ADC files begin with a fixed header, identifiable by a byte signature. The first four bytes are ASCII "adp " at offset zero in many examples; newer versions use a 32-byte header that starts with the magic number "ADC\0" (i.e. bytes 0x00434441 little-endian) and include fields such as sample rate, bit depth, channel count, number of blocks, and encoder build version. The payload that follows is a single continuous arithmetic-coded bitstream; there are no sync frames or seek tables in v0.82, making the file state-dependent from start to finish.

How to open ADC files

Important: Different programs may use files with the ADC file extension for different purposes, so unless you are sure which format your ADC file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested six different ADC openers which you will find listed below.

Last updated: August 17, 2026

All known file formats using extension .ADC

While Adaptive Differential Coding Audio is a popular type of ADC-file, we know of 2 different uses of the .ADC file extension. Different software may use files with the same extension for different types of data.

XemiComputers Active Desktop Calendar

The XemiComputers Active Desktop Calendar .ADC file is a proprietary "export" file format used by the desktop calendar program Active Desktop Calendar (ADC) from XemiComputers. It is produced when you choose to export your calendar data from within that application; it holds your calendar items - like appointments, tasks, notes, contact entries, alarms - as a bundled archive for backup or data transfer.

These .ADC files are read by Active Desktop Calendar itself when you choose to import them back; this restores all of the exported items. The typical workflow is: user creates or edits calendar content within ADC, exports to .ADC for safekeeping or moving to another computer, then re-imports inside ADC to restore.

Internally, these files begin with the ASCII header "XemiCo…" at the beginning of the file (bytes 0x58656D69436F at offset 0) and somewhere in the content they contain the text "EXPORTDATA," helping identify them as ADC's export bundles.

Various apps that use files with this extension

These apps are known to open certain types of ADC files. Remember, different programs may use ADC files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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