ADX Format Guide

Available Conversions

Convert to ADX

About ADX Format

ADX is a proprietary audio format developed by CRI Middleware, a Japanese company specializing in audio and video middleware solutions for video games. The format uses a custom ADPCM (Adaptive Differential Pulse-Code Modulation) compression algorithm specifically optimized for real-time audio playback in gaming environments. ADX was designed to provide efficient audio compression with minimal CPU overhead during decompression, making it ideal for platforms with limited processing power such as early gaming consoles. The format has been widely adopted by major Japanese game publishers, most notably SEGA and Capcom, and has been used across multiple console generations from the Sega Dreamcast through modern platforms including PlayStation, Xbox, and Nintendo Switch. ADX files typically achieve compression ratios of approximately 4:1 compared to uncompressed PCM audio while maintaining quality suitable for game sound effects, dialogue, and background music.

History of ADX

CRI Middleware (originally CRI, or Cross Road Inc.) developed the ADX format in the mid-1990s as part of their CRI Audio toolkit, which was initially created for the Sega Saturn console. The format gained widespread recognition with the Sega Dreamcast in 1998-1999, where it became the de facto standard for game audio across many SEGA titles including Sonic Adventure, Shenmue, and Jet Set Radio. CRI Middleware's close relationship with SEGA led to ADX being embedded deeply in Dreamcast game development toolchains. As the gaming industry transitioned to sixth-generation consoles (PlayStation 2, Xbox, GameCube), ADX was ported to these platforms and continued to be used by studios already familiar with the CRI toolset. Capcom became another major adopter, using ADX extensively in franchises like Resident Evil, Devil May Cry, and Street Fighter. The format evolved through several revisions, with CRI eventually developing the more advanced ADX2 toolkit that expanded on the original format's capabilities. Despite the emergence of competing formats like Sony's ATRAC and Microsoft's XMA, ADX maintained its position in Japanese game development due to CRI Middleware's strong developer support and the format's proven reliability across platforms.

Key Features and Uses

ADX uses a specialized ADPCM encoding that provides very fast decompression with minimal CPU load, a critical requirement for real-time game audio where processing resources must be shared with graphics, physics, and AI systems. The format supports sample rates from 8 kHz to 48 kHz and typically uses 4-bit ADPCM encoding, resulting in approximately 4:1 compression compared to 16-bit PCM audio. ADX supports both mono and stereo audio, with multi-channel configurations available through the ADX2 extension. A notable feature of ADX is its built-in loop point support, allowing seamless audio loops without gaps or clicks, which is essential for game background music that must repeat indefinitely during gameplay. The format also supports AHX, a variant that uses MPEG-2 encoding for higher quality music tracks. CRI's ADX toolkit provides platform-specific decoders optimized for each target hardware, ensuring consistent performance across different gaming platforms. The format includes header metadata for specifying loop start and end points, sample rate, channel count, and encoding parameters, all designed for efficient parsing during game runtime.

Common Applications

ADX is primarily used in video game development, particularly by Japanese game studios. The format serves as the standard audio format within the CRI Middleware ecosystem, which is used by hundreds of game titles across console, PC, and mobile platforms. SEGA has used ADX extensively across their franchises including Sonic the Hedgehog, Yakuza (Like a Dragon), Total War, and Phantasy Star Online. Capcom employs ADX in many of their major titles, and other prominent users include Konami, Bandai Namco, and Square Enix for select titles. Game developers typically use ADX for in-game sound effects, character dialogue, ambient sounds, and background music. The format's efficient decompression makes it suitable for situations where many audio streams must play simultaneously, such as complex game scenes with multiple sound sources. ADX is also used in Japanese arcade machines and pachinko/pachislot machines where CRI Middleware provides specialized audio solutions. The modding and game preservation communities frequently work with ADX files when extracting or replacing game audio assets, and tools like vgmstream and FFmpeg provide ADX decoding support for these purposes.

Advantages and Disadvantages