Nexo Player: AI Audio & Vault is an Android application designed for local media playback and file management. Its primary function is to play video and audio files stored on a device, generate narrated audiobooks from PDF and EPUB documents using offline AI voices, and provide a secure vault for private files. The app does not require a user account or cloud service integration, allowing users to access their existing media libraries directly from device storage. The application includes several core features. It supports local playback of video and audio files with controls for brightness, volume, orientation lock, subtitle styling, and background playback. A built in equalizer, waveform visualizer, and adjustable playback speed are also available. The AI audiobook feature converts PDF and EPUB documents into narrated audio, generating chapters and allowing export in M4B, MP3, or ZIP formats. Users can preview and select from dozens of offline narrator voices, filtering by language, gender, and style. The Secure Vault component enables users to hide files behind PIN or biometric authentication, with encrypted storage and a built in image gallery. Additional tools include a text to speech function for typed or pasted text, an EPUB reader with chapter navigation and bookmarks, and Chromecast support for streaming to televisions or speakers. Typical use cases involve playing local media files without reshaping a library around a cloud service, converting reading materials into listenable audiobooks for offline consumption, and protecting sensitive files from other applications. The workflow begins with opening a video, audio, PDF, or EPUB file from device storage. For audiobook creation, users select a document, preview and choose an offline AI voice, and generate the narration in the background. Private files can be locked in the vault using PIN or fingerprint. The app is designed to function entirely offline for its core features, including voice preview and narration generation. Technically, the app is available on the Google Play Store and is developed by CodeBitByBit.com. It requires no account to start and processes files locally on the device. The app supports common media formats and document types, with narration generation occurring on device without requiring an internet connection.