This guide explains how to convert an .asf file to an .avi without re-encoding.

You will need the following software in this guide:


There's one prerequisite for that method to work: The video must be encoded using MS MPEG-4 v2 or MS MPEG-4 v3 (or DivX3), it cannot be Windows Media Video 7 (WMV1) or Window Media Video 8 (WMV2).

In order to find this out play the video in Windows Media Player 6.4 (c:\program files\windows media player\mplayer2.exe, it's available in W98, WinME, W2K and WinXP). During playback right click in the window and select properties. Then go to the advanced tab where you'll see something like this:

In this case we have WMA8 audio and WMV7 video. In other words, this method won't work and you'll have to re-encode.

If it's something like this we're lucky and this method will work.

Start up AsfTools, press the Add button and select your .asf file. Then press the Advanced button and go to the Convert to AVI tab.

These options should be sufficient so all you have to do is press Convert. If synch should be off try the Best Audio/Video Sync option in this screen.

If the ASF is corrupt this program will give you various options to fix whatever is recoverable but that goes beyond the scope of this guide. Make sure you read the FAQ at the official AsfTools site.

After conversion I had to install DivX3.11alpha as WMP would no longer find an audio codec to play the included audio file.