Windows Media Video (WMV) Format: What You Should Know

What Is the WMV Format?

A Windows Media Video (WMV) file format contains videos compressed with WMV compression and saved in Microsoft Advanced System Format (ASF). This video format supports encryption for digital rights management (DRM) systems and high-definition (HD) video. It can store various videos, including video clips, animations, movies, and TV episodes.

Microsoft introduced the WMV Video, Screen, and Image codec in 1999 as part of the Windows Media framework. Since then, it has become a popular codec, widely used to compress and convert ASF videos to WMV files. You can play WMV on various media players, Windows and otherwise, and stream it over the Internet.

The first version, VMV 7, was based on MPEG-4 Part 2. Microsoft continued development of the format, and its proprietary bit stream syntax was frozen in WMV 9. This version introduced several important features including:

  • Native support for interlaced video
  • Non-square pixels
  • Frame interpolation
  • A profile called Windows Media Video 9 Professional which is used automatically when resolution exceeds 300K pixels and bitrate exceeds 1000 kbit/sec.

Related content: Read our guide to video codecs

In this article:

WMV File Format Specifications

The WMV format is usually packed into ASF containers, but Matroska and AVI containers also support WMV with the .mkv and .avi extensions. WMV-9 is the latest, best codec available in Windows Media Video, offering low bit-rate compression. It has an 8-bit 4:2:0 color format and uses block-based spatial transformation and motion compensation.

WMV uses a motion vector to help compensate for motion between frames. It forms each block by predicting values based on preceding reconstructed frames, calculating the residual error between the actual and predicted block. A linear quantized, entropy-encoded transform is used to transform the residual error (which the decoder side then decodes and de-quantizes).

WMV 9 has three types of frames: intra I frames (independently coded); predicted P frames (dependent on a previous frame); bi-directionally predicted B frames (with references in the past and future). WMV-9 does not use the bi-directional (B) frames as references for other frames, so they remain outside the decoding loop.

Windows Media Video Format Variants

In addition to the basic WMV format, there are two additional variants of the format designed for special use cases: WMV Screen and WMV Image.

Windows Media Video Screen

The Windows Media Video 9 Screen codec is designed for screenshots of applications intended to be shown on a computer display. For example, it can be used to transmit screen images when remotely accessing computer systems.

This codec assumes that a screen image is relatively simple, with fewer colors, more straight lines, and less motion than typical video content. It uses these characteristics to achieve very high compression compared to the WMV Video codec.

Windows Media Video Image

Windows Media Video Image is a slideshow format, which contains a series of images and applies effects like timing, panning, and transitions during playback. For still images combined into a slideshow, it can achieve higher compression than the WMV 9 Video codec. A new version of the format, WMV 9.1 Image, supports more transformation effects between slides, but is not backward compatible.

A downside of this format is that it requires the player to generate video frames in real-time. Playing WMV Image files at moderate resolution, for example 1024×768 with 30 fps, requires a large amount of processing power.

WMV Format Pros and Cons

Here are the main advantages of using the WMV format:

  • The WMV format keeps a large quantity of audio and video data in smaller storage spaces, making it ideal for streaming videos over the Internet.
  • The WMV format is the default format in several Windows devices and is compatible with all Windows devices.
  • Many legacy applications, including older versions of PowerPoint, support the WMV format.
  • WMV offers a 2x compression ratio compared to MPEG-4.
  • It is one of the smallest video formats, ideal for email attachments.
  • You can use Google Drive to make the format available online.
  • You can use it with many converters.

Here are the main disadvantages of using the WMV format:

  • The WMV format is proprietary to Microsoft and not compatible with other operating systems. However, there are Apple-based and Linux media players that can run WMV files, such as Apple’s Flip4Mac WMV QuickTime component.
  • All WMV files use a digital rights management system. These systems, particularly Windows Media Player 11, often make it impossible to restore the licensing information attached to WMV files.
  • Not all applications are designed to work with the small file size produced by the WMV format.
  • The term WMV refers to the file container format as well as the Windows Media Video codec. As a result, it can be difficult to determine whether a WMV file contains compression by other supported codecs.

How Do You Convert WMV to MP4 Or WebM Format With Cloudinary?

The WMV format is proprietary to Microsoft and is not compatible with many devices and applications. Cloudinary can help you automatically convert M4V files to modern video formats for faster loading, and an enhanced user experience.

Cloudinary performs the task in the cloud through automation in three steps:

  1. Convert M4V to MP4s or WebM through dynamic URLs.
  2. Resize, crop, and transform the videos generated in step 1.
  3. Optimize the transformed videos through a fast content delivery network (CDN).

The conversion capability is available in all Cloudinary plans, including the free tier. Do check it out.