File Content Extraction 25.4
Filter SDK C Programming Guide

# Architectural Overview

The general architecture of File Content Extraction is the same across all supported platforms and is illustrated in the following diagram.

Each component is described in the following table.

Architectural Components

Component | Description
--- | ---
Developer's Application | Your application.
File Extraction API | The File Extraction API opens a file and extracts the file's subfiles so they are exposed for filtering. See Use the File Extraction API.
Filter API | The Filter API exposes the filtering functionality and controls all other modules during the filtering process. See Use the Filter API.
Format Detection | This module determines the file type of the input stream, allowing the Filter API to return that information to the developer's application, or to load the appropriate structured access layer for further processing. See Obtain Format Information for more information about format detection.
Structured Access Layer | There are three main modules that reside in the structured access layer—one each for word processing, spreadsheet, and presentation formats. The file detection result determines which structured access layer module is used during the filtering process. That module loads the appropriate document reader and proceeds with text extraction or metadata retrieval.
Document Readers | Each document reader reads a specific file format and sends a text stream of the document to the structured access layer. Each filter is loaded as required by the structured access layer. See Document Readers for a complete list of document readers.

## Out-of-Process Filtering

By default, Filter runs independently from the calling application process. This approach is called out-of-process filtering. Out-of-process filtering protects the stability of the calling application in the rare case when a malformed document causes Filter to fail.

When you run File Content Extraction, each out-of-process session uses the following processes:

- `extract_kvoop.exe` This process performs subfile extraction.

- `filter_kvoop.exe` This process does all other File Content Extraction processing.

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Version 25.4 | Last updated October 2025

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Product: File Content Extraction 25.4

Topic Title: Architectural Overview