What are the differences between ASF and WMV file formats?

[physics223]

Well, that's simply my question. What are their differences? What provides greater compression - no, better compression - or, which has better size to quality ratio?

Another side question - I really am a n00b ... , but, is this correct: RM/RMVB files have a better compression and size-to-quality ratio than WMV files? In all the times I've practiced encoding with these files, I always found out that the RM/RMVB file format had a better (meaning lesser) file size at the same quality as WMV files. So I concluded that they have better compression than WMV files. Am I correct? Can someone point me to technical sites/references to support this thought of mine?

I really like studying the different media formats [plus, it's really important for our school lessons], so I'd be really glad if someone could at least enlighten me.

Thank you for reading, and thanks for your time. I hope you're cool with me. 8)

[Poplar]

As I understand it, WMV is the superset of ASF. I guess Microsoft didn't like the name ASF (Advanced Streaming Format), which sounded very limited, so they changed it to WMV. You can changed ASF extension to WMV and WMP will play it.

Personally, I don't like RM/RMVB. Won't touch then unless absolutely necessary. In this part of the world, RMVB is pretty much limited to streaming online video. But I just found out RMVB is quite popular in Asia, where you are from. I don't know why.

As for which format has the best compression and quality, it's very subjective and I won't get into it. But in the world I am familiar with, Xvid/Divx is the king.

[celtic_druid]

Yep, WMV = ASF and rmvb = rm. In both cases it was changed to make a distinction. ASF files used to contain MS MPEG4 and WMA, they renamed it to WMV to contain WMV and rmvb was renamed when Real Video 9 came out as previous codecs were CBR only for streaming purposes.

Since technically rmvb and wmv are both containers if you wanted to compare quality at a given filesize then it would be about overhead. The container with the lowest overhead is capable of better quality as it leaves more space to use a higher bitrate for your video and audio.

Although in this case you have WMV with WMV and WMA and rmvb with Real Video 9EHQ/10 and cook/aac audio.

So you could ditch rmvb/wmv and store them both in mkv if you want to compare the video or audio.

As to whether WMV 9 or RV 10 is better quality. That depends on personal tastes and the source/settings.