AVI Format Guide

Available Conversions

About AVI Format

AVI (Audio Video Interleave) is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology, designed to bring video playback capabilities to the Windows 3.1 operating system. AVI was one of the first widely-adopted video formats for personal computers, predating MPEG standards and establishing fundamental concepts for digital video storage and playback that influenced subsequent container formats. The name "Audio Video Interleave" describes its core technical approach: interleaving audio and video data in alternating chunks, allowing synchronized playback even on systems with limited processing power and slow storage devices like CD-ROM drives—a critical constraint in the early 1990s when CPUs operated at 25-66 MHz and hard drives delivered 1-2 MB/s throughput.

AVI is based on Microsoft's RIFF (Resource Interchange File Format) specification, a general-purpose container structure originally developed for multimedia data. RIFF uses a hierarchical chunk-based architecture where data is organized into tagged blocks ("chunks") containing either data or other chunks, creating a flexible structure that can accommodate diverse media types, metadata, and future extensions. An AVI file consists of a RIFF header identifying it as an AVI file, followed by chunks containing video frames, audio samples, index information for seeking, and metadata about codecs, dimensions, frame rates, and other parameters. This chunk-based structure made AVI extensible and codec-agnostic—the same container could hold video compressed with various codecs including Motion JPEG, Cinepak, Intel Indeo, and later MPEG-4 Part 2 (DivX/Xvid) and H.264.

During the 1990s and early 2000s, AVI became the dominant video format for Windows PCs and established itself as the de facto standard for video capture, editing, and sharing on desktop computers. The format's universality was reinforced by its deep integration into Windows—built-in playback through Windows Media Player, native support in video editing applications, and codec infrastructure allowing third-party developers to add support for new compression formats. The late 1990s and early 2000s saw the "DivX era" where MPEG-4 Part 2 video codecs (DivX and the open-source Xvid) stored in AVI containers revolutionized video distribution, allowing users to compress full-length movies to 700 MB files that fit on a single CD-R while maintaining acceptable quality—enabling widespread video sharing via CD-ROM and early broadband internet connections.

However, AVI's limitations became increasingly apparent as video technology advanced. The original AVI specification used 32-bit values for file sizes and chunk offsets, imposing a hard 2 GB file size limit that became problematic as video quality improved and recording durations increased. OpenDML extensions (AVI 2.0), introduced in 1996, addressed this with a hierarchical index structure allowing files exceeding 4 GB, but support remained inconsistent across software. AVI also lacked robust support for modern features taken for granted in newer formats: limited metadata storage (no chapters, descriptions, or cover art), no native support for multiple audio tracks or subtitles, poor variable bitrate handling, and inadequate support for modern codecs like H.264 and HEVC which require sophisticated container features for proper operation. By the mid-2000s, MP4 and MKV (Matroska) emerged as superior alternatives offering better codec support, extensive metadata, multiple tracks, chapters, and no practical file size limits, gradually displacing AVI as the preferred container for video storage and distribution.

History of AVI

AVI's creation was driven by Microsoft's ambition to establish Windows as a multimedia platform competitive with Apple's QuickTime, which had launched in December 1991 and demonstrated that personal computers could handle video playback. Prior to Video for Windows, playing video on a PC required expensive specialized hardware like dedicated video capture cards and overlay boards. Microsoft assembled a team to develop Video for Windows, a software framework enabling video playback, recording, and editing using only CPU processing—"software codec" approach that was revolutionary but required efficient compression and container formats to work within the severe hardware constraints of early 1990s PCs (386/486 processors, 4-8 MB RAM, 100-200 MB hard drives).

Video for Windows 1.0 launched in November 1992, bundling Windows 3.1 with tools for video capture, editing (VidEdit), and playback, along with the AVI container format and several codecs including Microsoft Video 1 (a simple RLE-based codec), Microsoft RLE (run-length encoding for simple animations), and support for third-party codecs like Cinepak (developed by SuperMac) and Intel Indeo. These codecs delivered modest quality at high compression ratios, necessary because 1990s CD-ROM drives operated at 150 KB/s (1x speed), requiring video bitrates below 100-120 KB/s to enable playback without buffering. Early AVI files typically contained 160×120 or 320×240 resolution video at 15 fps, heavily compressed with blocky artifacts visible even on the low-resolution CRT monitors of the era, but this was acceptable given the novelty of video on PCs.

Throughout the mid-1990s, AVI became the standard video format for Windows multimedia applications. Video capture cards from manufacturers like Matrox, Pinnacle, and Miro recorded video as AVI files using hardware codecs (Motion JPEG was popular for capture quality, offering reasonable compression with frame-independent encoding ideal for editing). CD-ROM multimedia titles—encyclopedia software, edutainment programs, games with FMV (full-motion video) sequences—delivered video content as AVI files compressed with Cinepak or Indeo codecs. Microsoft bundled progressively improved versions of Video for Windows with Windows 95 and Windows 98, ensuring AVI playback support on hundreds of millions of PCs and establishing it as the universal video interchange format for Windows. Apple's QuickTime for Windows provided an alternative, but AVI's native Windows integration gave it dominant market share on the PC platform.

The late 1990s brought transformative change with the emergence of MPEG-4 Part 2 codecs and the "DivX revolution." In 1998, a hacker group called DivX Networks reverse-engineered Microsoft's MPEG-4 V3 codec and released "DivX ;-)" (later DivX 3.11), an MPEG-4 Part 2 codec offering dramatically better compression than previous AVI codecs—enabling full-length movies at DVD-like quality in 700 MB files that fit on CD-Rs, which had become affordable for consumers (~$1-2 per disc by 1999). The open-source community responded with Xvid (DivX spelled backwards), a free MPEG-4 Part 2 codec providing similar quality. Both codecs stored their output in AVI containers, leveraging AVI's universal Windows support. This sparked an explosion of video sharing via CD-R distribution and emerging broadband internet connections (cable and DSL), with millions of users encoding, sharing, and playing DivX/Xvid AVI files throughout the early 2000s.

The early-to-mid 2000s represented AVI's peak ubiquity. Video editing software (Adobe Premiere, Sony Vegas, Pinnacle Studio, Windows Movie Maker), video capture hardware (TV tuner cards, camcorder capture), and media players (Windows Media Player, VLC, Media Player Classic) all provided robust AVI support. Digital cameras and camcorders recorded video as AVI files using Motion JPEG or DV codecs. However, AVI's limitations became increasingly problematic: the 2 GB file limit (or 4 GB with OpenDML) restricted recording durations, particularly for high-quality captures; the format's poor support for variable frame rates, variable bitrate audio, and modern codec features like B-frames created compatibility issues; and the lack of metadata, chapters, and multiple audio/subtitle tracks made AVI inadequate for professional and commercial video distribution.

By 2005-2010, MP4 and MKV emerged as superior alternatives that addressed AVI's shortcomings. MP4 (MPEG-4 Part 14), standardized by MPEG and based on Apple's QuickTime format, offered excellent H.264 codec support, extensive metadata, multiple tracks, and no practical file size limits—becoming the standard format for digital cameras, smartphones, streaming services, and video distribution. MKV (Matroska), an open-source container, provided even greater flexibility with support for virtually any codec, unlimited tracks, chapters, attachments, and sophisticated features for high-quality video archival and distribution—becoming the preferred format for enthusiasts and for distributing high-definition video. Hardware devices including smartphones, tablets, smart TVs, and media players standardized on MP4 playback, often omitting AVI support entirely.

Today, AVI persists primarily as a legacy format. Billions of AVI files exist in archives from the 1990s-2000s era containing personal videos, digital camera recordings, and video content from that period. Some specialized applications still output AVI (particularly for uncompressed or Motion JPEG video where the container's simplicity is advantageous), and certain legacy video editing workflows maintain AVI support for compatibility with older projects. However, for new video creation, AVI has been effectively superseded by MP4 (for general use, streaming, and device compatibility) and MKV (for high-quality archival and enthusiast distribution). The format remains an important milestone in digital video history, demonstrating that the core concepts it established—container/codec separation, chunk-based structure, interleaved audio/video—proved sound and influenced all subsequent video container formats.

Key Features and Uses

AVI's RIFF-based structure organizes data as nested chunks identified by four-character codes (FourCC). A typical AVI file begins with a RIFF header containing the 'AVI ' identifier, followed by a 'hdrl' (header list) chunk containing 'avih' (AVI header with global parameters like frame rate, number of streams, file size), 'strl' (stream list) chunks for each audio/video stream describing codec, format, and timing information, and optionally 'odml' (OpenDML) chunks for extended index support in large files. The actual media data resides in an 'mdat' (movie data) chunk containing interleaved audio and video frames, each tagged with their stream ID and size. Finally, an 'idx1' (index) chunk provides frame offsets for seeking—critical for random access to specific timestamps without parsing the entire file.

The interleaving strategy is fundamental to AVI's design and name. Rather than storing all video data followed by all audio data (which would require large buffers and complex synchronization), AVI alternates small chunks of video frames and audio samples. For example: video frame 1, audio samples for frame 1's duration, video frame 2, audio samples for frame 2's duration, and so on. This interleaving enables simple synchronized playback: read the next chunk, send video to video decoder or audio to audio decoder, repeat. The interleaving granularity is configurable but typically set to approximately 0.5 to 1.0 seconds—balancing synchronization tightness against seek performance and overhead. This approach was essential for 1990s hardware where reading large sequential blocks from CD-ROM was efficient but seeking was slow (200-300ms), and where RAM constraints (4-16 MB) limited buffer sizes.

AVI's codec flexibility is both a strength and weakness. The format uses FourCC codes (four-character identifiers like 'MJPG' for Motion JPEG, 'DIVX' for DivX, 'XVID' for Xvid, 'H264' for H.264) to identify which codec compressed the video, with codec-specific details stored in codec-private structures. This allows AVI to contain virtually any video or audio codec—the container just stores compressed data without understanding its contents. However, this creates the infamous "codec hell" problem: playing an AVI file requires having the specific codec installed that was used to encode it. Users downloading DivX AVI files in the early 2000s frequently encountered "codec not found" errors, requiring codec pack installations (K-Lite Codec Pack, Combined Community Codec Pack) to acquire the necessary decoders—a source of frustration and security concerns (malicious codec installers spreading malware).

AVI's original 2 GB file size limitation stems from its use of 32-bit unsigned integers for chunk sizes and file offsets, limiting values to 2^32 bytes = 4 GB, with additional practical limits bringing it to ~2 GB for compatibility. For 1990s video at 1-2 Mbps bitrates, 2 GB accommodated 2-3 hours of video—adequate for most uses. However, as video quality improved (DVD-quality video at 4-6 Mbps, high-definition at 10-20 Mbps), the 2 GB limit became restrictive. OpenDML extensions (AVI 2.0 specification from Matrox OpenDML Group, 1996) addressed this by introducing a hierarchical index ('indx' super-index chunks containing pointers to standard 'idx1' index chunks), splitting large files into multiple segments within a single AVI file, enabling files exceeding 4 GB. However, OpenDML support varied: professional video editing applications generally supported it, but consumer software and hardware players often did not, creating compatibility concerns.

AVI's metadata support is minimal compared to modern formats. The format lacks standardized fields for video title, description, copyright information, poster images, chapters, or rich metadata—information routinely stored in MP4 (via iTunes metadata atoms) and MKV (via tags and attachments). Some applications store metadata in INFO list chunks (similar to WAV file metadata), but this is non-standard and poorly supported across players. AVI also provides no native support for multiple audio tracks (for different languages), multiple subtitle streams, or alternative camera angles—features common in modern video containers. These limitations make AVI unsuitable for commercial video distribution, streaming services, and any application requiring rich metadata or multiple track variants.

AVI's codec support encompasses both legacy and modern options, though with varying degrees of success. Traditional AVI codecs include Motion JPEG (common for video capture and editing due to frame-independent compression), DV codec (for digital camcorder footage), Cinepak and Indeo (legacy codecs from 1990s), uncompressed RGB or YUV (for maximum quality but enormous file sizes), and DivX/Xvid (MPEG-4 Part 2 codecs that dominated 2000s video sharing). Modern codecs like H.264 and H.265/HEVC can be stored in AVI containers using appropriate FourCC codes, but this is problematic: these codecs require sophisticated container support for features like B-frame reordering, timing information, and codec configuration—support that AVI's simple structure doesn't provide. As a result, H.264-in-AVI files often have playback issues, poor seeking, or incompatibility with hardware players. MP4 and MKV provide the proper container infrastructure these modern codecs require.

Common Applications

Legacy video archives represent the primary contemporary relevance of AVI. Billions of AVI files were created from the mid-1990s through the late 2000s, documenting personal memories, events, and content from that era. Home videos captured from analog camcorders via capture cards, digital camcorder footage recorded in DV-AVI format, wedding videos and event recordings, digitized VHS tapes, and early digital camera video clips all frequently exist as AVI files. Many users maintain these archives on hard drives, optical discs, or backup storage, occasionally needing to view, edit, or convert them to modern formats for compatibility with current devices that may lack AVI codec support.

Video capture and editing workflows in certain specialized applications continue using AVI due to its simplicity and low overhead. Professional video capture cards and systems recording uncompressed or Motion JPEG video often output AVI files because the format's straightforward structure minimizes processing overhead during high-bitrate capture—critical when capturing uncompressed 1920×1080 video at 1.5 Gbps (gigabits per second), where any processing delays would cause dropped frames. Similarly, some scientific and industrial imaging applications (high-speed cameras, microscopy, machine vision) use AVI with uncompressed or lossless codecs for frame-accurate recording with minimal processing latency. However, even these applications increasingly migrate to more modern containers like MXF (Material Exchange Format) or ProRes/DNxHD workflows in MOV containers.

DivX/Xvid distribution, while largely historical, represents an important chapter in internet video sharing. From approximately 1999 to 2008, before YouTube's dominance and before widespread broadband enabled easy video streaming, millions of users shared video content as DivX or Xvid AVI files—distributed via CD-ROM, DVD-ROM, FTP servers, BitTorrent, and early file-sharing networks (Napster, Kazaa, eDonkey, BitTorrent). These files typically contained full-length movies compressed to 700 MB (CD-size) or 1.4 GB (DVD-size), television episodes at 175-350 MB, or anime episodes at 230 MB ("standard" sizes that emerged as community conventions). Specialized media players like VLC, Media Player Classic, and KMPlayer with codec packs enabled playback. This ecosystem has largely disappeared, replaced by streaming services, but significant archives of DivX/Xvid AVI content persist on storage media and backup archives.

Digital cameras and camcorders from the 2000s recorded video as AVI files, leaving millions of users with AVI archives from that period. Consumer digital cameras from manufacturers like Canon, Nikon, Sony, Olympus, and Panasonic frequently recorded video as Motion JPEG AVI files (due to the codec's simplicity and the fact that still camera hardware could easily compress JPEG frames). Digital video camcorders using DV tape (MiniDV, DVCPro) transferred footage to computers as DV-AVI files via IEEE 1394 FireWire connections, with the DV codec preserving the original tape quality for editing. Later, hard-disk and flash-memory camcorders sometimes used AVI containers with MPEG-4 Part 2 codecs. As these devices have been replaced by smartphones and modern cameras recording H.264 MP4 video, the AVI files they produced remain in users' archives, sometimes requiring conversion for playback on modern devices.

Windows Media Player and legacy software ecosystems maintain AVI relevance. Windows Media Player, bundled with every version of Windows through Windows 10, plays AVI files with appropriate codecs installed. Older Windows PCs (particularly Windows XP through Windows 7 systems still in use in some contexts—legacy industrial systems, isolated networks, retro computing environments) retain full AVI support. Legacy video editing projects created in older versions of Adobe Premiere, Sony Vegas, Pinnacle Studio, or Windows Movie Maker often reference AVI source files, requiring AVI support to reopen and modify these projects. Organizations and individuals maintaining video archives from the 1990s-2000s frequently need AVI playback and conversion capabilities to access this legacy content.

Screen recording and gameplay capture software sometimes outputs AVI files, particularly when using uncompressed or lossless codecs for maximum quality capture. Applications like OBS Studio, XSplit, Fraps, and Bandicam offer AVI as an output option (often with Motion JPEG, uncompressed, or lossless codecs like Lagarith or Ut Video Codec) for capturing screen activity, software demonstrations, or gameplay footage at native quality without compression artifacts. The AVI files are then typically re-encoded to H.264 MP4 for final distribution. However, even this use case increasingly shifts to direct H.264 recording to MP4/MKV or to specialized intermediate codecs (ProRes, DNxHD) in MOV containers, as AVI's limitations become more problematic with high-resolution, high-frame-rate capture.

AVI-to-MP4 conversion represents one of the most common video conversion tasks today. Users with AVI archives seeking to play videos on smartphones, tablets, smart TVs, or game consoles—devices often lacking AVI codec support—must convert AVI files to MP4 format. This conversion ideally involves re-encoding the video with H.264 codec and audio with AAC codec within an MP4 container, producing files with universal compatibility. Online conversion services, desktop applications (HandBrake, FFmpeg, VLC), and video editing software all provide AVI-to-MP4 conversion functionality. The ubiquity of this conversion need reflects AVI's legacy status: a format that was once universal now requires conversion for compatibility with current technology.

Advantages and Disadvantages