AVI File Size Limits

 

 

Introduction

When working with digital video, you often have to deal with AVI files that are many gigabytes in size.  Until recently, however, many computers were not designed to support files of such a large size.  Because of this, people often have trouble when creating large AVI videos.

The two most common limits that people reach are the 2 GB and 4 GB barriers.  These barriers are caused by two factors:  the limits of the standard AVI file format and the file system of your operating system.


The Limits of the Standard AVI File Format

The Problem:

Many applications, especially older ones, use the Video for Windows architecture, which limits AVI files to 2 GB in size.  Standard AVI files can be up to 4 GB in size if other methods of handling AVIs are used.  However, those other methods are rarely used.

Solutions:

1)  OpenDML 1.02:  This is an extension to the AVI file format that allows AVI files to be of any size.  To create and work with OpenDML AVIs, you need software that supports the OpenDML standard (such as VirtualDub).

2)  Segmented AVIs:  By breaking your AVI files into smaller chunks, like 2 GB or 4 GB pieces, you can create videos of any length or size.  To create and work with segmented AVIs, you need software that supports them (such as AVI_IO, VirtualDub, or Avisynth).

3)  Avisynth:  This little utility enables many programs with a 2 GB limit to open AVI files of any size.  It also has many other functions, such as joining segmented AVIs and processing your videos.


The Limits of File Systems

The Problem:

In order to store files on a hard drive, your computer uses a file system.  Depending on your operating system, there are many different file systems that you may be using.  Here is a table that lists the maximum file sizes for different operating systems and file systems:

  Windows 95
(pre-OSR2)
Windows 95 OSR2+,
Windows 98/SE/ME
Windows NT 4.0 Windows 2000/XP
FAT16 2 GB 2 GB 4 GB 4 GB
FAT32 N/A 4 GB N/A 4 GB
NTFS N/A N/A Nearly unlimited Nearly unlimited

The underlined values represent the most common file systems and limits for each respective operating system.

Solution:

1)  Segmented AVIs:  The only way to get around file system limitations is to use segmented AVIs.  You must keep the segments equal to or smaller than the maximum file size for your file system.  To create and work with segmented AVIs, you need software that supports them (such as AVI_IO, VirtualDub, or Avisynth).


Summary

Here is a quick list of common computer setups and their limitations:

A)  If you are running an early version of Windows 95 (before OEM Service Release 2), your AVI files are limited to 2 GB.

B)  If you are running Windows 95 (after OEM Service Release 2), Windows 98, Windows 98 SE, or Windows ME with the FAT32 file system (as most people are), your AVI files are limited to 4 GB.

C)  If you are running Windows NT 4.0 or Windows 2000/XP with the NTFS file system, your AVI files can be of virtually unlimited size.

D)  If you are running Windows 2000/XP with the FAT32 file system (this is less common), your AVI files are limited to 4 GB.