Advanced Streaming Format is limited to MPEG-4 video which is not much of a limitation as it very flexible and results in the highest quality at a given bitrate, and Windows Media Audio which is generally good but MP3 is better in some cases. The primary advantage is the ability to stream (hence the name). The main disadvantages are fewer tools to create and work with them and a larger file size. ASF tools generally limit the frame size and bitrate so it is often necessary to actually create an MPG4/WMA AVI and then convert it directly (not re-encode) to ASF, which shows that the larger size only comes from the streaming overhead for the exact same quality. So, since the Audio Video Interleave transport can use many different codecs for audio and video, including those mentioned and has more tools available for it and is a smaller size for the same quality it is superior in every instance except where streaming is absolutely required. Encoding with the latest MS MPEG-4 codec of course require a hack since at some version in the development MS decided to limit its offical use to ASF. But no matter as DivX ;-) has become virtually the standard amongst hacked versions and even then it is only required to encode. The final file can have its header changed back to MPG4 so DivX ;-) is not even required for playback.