What is MIME type "audio/adpcm"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

audio/adpcm is the MIME type for audio files using the Adaptive Differential Pulse-Code Modulation codec.
This codec compresses audio data by encoding only the changes between samples.
It lowers the data rate while keeping resource use low, which is useful where bandwidth or storage is limited.

Used in voice recording and telephony systems.
Common in multimedia applications requiring efficient audio compression.
Favored in environments with limited processing power.

Its main file example is the ADP file.
For more details on ADPCM, check out its overview on Wikipedia.

Associated file extensions

.adp

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: audio/adpcm

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="audio/adpcm">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');    
    
    http.createServer((req, res) => {    
      res.setHeader('Content-Type', 'audio/adpcm');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.adp

FAQs

Do web browsers natively support audio/adpcm playback?

No, most modern browsers (Chrome, Firefox, Safari) do not natively support raw audio/adpcm files via the HTML5 <audio> element. To ensure audio plays for all users, you should convert .adp files to widely supported formats like MP3 or WAV before embedding them.

How do I configure Apache to serve .adp files?

You must explicitly map the extension to the MIME type in your server configuration or .htaccess file. Add the line AddType audio/adpcm .adp to ensure the server sends the correct headers, allowing the client to identify the file as ADPCM audio rather than a generic binary stream.

Why does IIS return a 404 error for .adp files?

Microsoft IIS often blocks file extensions that are not explicitly defined in its MIME map for security reasons. To fix this, open the MIME Types feature in IIS Manager and add a new entry with the file extension .adp and the MIME type audio/adpcm.

What is the difference between audio/adpcm and audio/wav?

While WAV usually contains uncompressed Pulse-Code Modulation (PCM) audio, audio/adpcm uses Adaptive Differential PCM to compress the data. This compression records the difference between samples rather than the absolute value, significantly reducing file size while maintaining acceptable quality for voice applications.

How can I open or convert an ADP file?

Standard media players may fail to open standalone .adp files; versatile tools like VLC Media Player or command-line utilities like FFmpeg are recommended. You can use FFmpeg to convert the file to a more common format using a command like ffmpeg -i input.adp output.mp3.

Is audio/adpcm suitable for high-quality music streaming?

Generally, no. ADPCM is a lossy compression algorithm optimized for telephony and voice recording where low CPU usage and bandwidth are prioritized over high fidelity. For music, formats like AAC or Ogg Vorbis provide superior audio quality at similar or lower bitrates.

General FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.