.WMV

Introduction

A .wmv file is Windows Media video: video in one of Microsoft’s Windows Media Video codecs, usually with Windows Media Audio, stored in Microsoft’s Advanced Systems Format (ASF) container. It was the usual video file on Windows in the late 1990s and 2000s and was played by Windows Media Player.

The container is the same whatever the content. Files are named .wmv for video, .wma for audio only and .asf for anything else, such as other codecs.

Structure

An ASF file is a sequence of objects. Each starts with a 16-byte GUID that gives its type and a 64-bit little-endian size. The file begins with the Header Object, GUID 30 26 B2 75 8E 66 CF 11 A6 D9 00 AA 00 62 CE 6C as stored on disk, which holds further objects: the file properties, one stream properties object per stream, and optional metadata such as the title. The Data Object follows with the media cut into fixed-size packets, and optional index objects at the end help seeking.

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