What is an ACT file?
The .act file extension represents several specialized and unrelated formats, making its identification crucial. Primarily, in the Adobe ecosystem, an ACT file is an Adobe Color Table (or Color Lookup Table), a database format used in Adobe Photoshop and Illustrator. This type of ACT stores a predefined set of colors, allowing designers to add or remove specific swatches when saving images for online use. This control is essential for optimizing the balance between visual quality and smaller file sizes for web publishing.
However, it is critical to perform format identification, as the same extension can refer to an entirely different file type. For instance, an ACT file might not be a color table but an ADPCM (Adaptive Differential Pulse Code Modulation) Encrypted Audio file, a compression standard utilized by various voice recorders and music listening devices. Beyond multimedia, the ACT format is also integral to the Alma CAD/CAM system, where it contains guidelines that instruct 3D machine tools on how to cut materials. Other examples include actor files for the Genesis3D Player, action files for DS game development, and schematic files for the FoxPro Detailing Wizard.
Key Characteristics of ACT Files
| Characteristic | Description |
|---|---|
| Full Name | Adaptive Coding Technology / Active Voice Technology |
| File Extension | .act |
| Primary Use | Voice recording on digital recorders and older MP3 players |
| Audio Encoding | Lossy Compression |
| Compression Type | Adaptive (adjusts based on audio content) |
| Bitrate Range | Very Low (~8 kbps to ~32 kbps) |
| Channels | Typically Mono |
Optimized for Speech, Not Music
The ACT format is a specialist, not a generalist.
- Frequency Range: Human speech typically occupies a frequency range of 85 Hz to 4 kHz. The ACT codec is tuned to this range, effectively discarding higher and lower frequencies that are less critical for speech intelligibility. This focus allows for much more aggressive compression than a format designed for full-spectrum music.
- Result: While this makes ACT files extremely small, it also means they produce very poor-quality music recordings, as the high and low frequencies are lost.
ACT File Format Specification
Many recorders using the ACT system only are doing it for the smallest recording option; if the quality is upped, a separate format, usually WAV, is used, resulting in massively larger documents.
There are several generations of ACT; as of June 2009, tracks created by subsequent devices just can not be recognized by every free standard music player or converter application, leaving only the bundled MP3 tools.
Image optimization for Web distribution is done with ACT files. Customers can test the picture quality against the generated image databases by increasing or decreasing the number of colors in the CLUT.
By tapping the Color Table option and picking Load Color Data from the Export for Web dialogue box, Adobe color tables can be uploaded. The /Presets/en_US/Save for Web Settings/Color Tables/ directory contains several preconfigured ACT files that came with the Photoshop system.
Act scripts can be generated solely within Genesis 3D or by transforming other 3D models to the ACT standard using Genesis3D Actor Designer
FAQ
Q1: How do I play an ACT audio file on my computer?
A: You can use media players like VLC or foobar2000, or convert them to a more common format like MP3 using a dedicated tool like FFmpeg.
Q2: Why is my ACT recording so small?
A: The ACT format uses highly aggressive, speech-optimized compression to minimize file size, allowing for extremely long recording times.
Q3: Can I convert an ACT file to MP3?
A: Yes, conversion is possible using audio conversion software, though the output quality will still be limited by the original low-bitrate ACT source.
Q4: Is ACT a high-quality format?
A: No, ACT is a low-quality format specifically designed for intelligible speech, not high-fidelity music or audio.
Q5: Why won’t my media player open my ACT file?
A: The proprietary nature of the format means not all players support it. Header variations from different recorder manufacturers can also cause compatibility problems.
