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View Full Version : Does WMV9 use B-frames?

fccHandler
8th July 2006, 22:54
I haven't had any luck finding confirmation from Microsoft one way or the other about this, so I'll just ask. I know that the Advanced Profile codec can use B-frames, but are they also used by the regular WMV9? (I'm speaking of WMV files encoded with Windows Media Encoder 9.)
zambelli
8th July 2006, 22:59
Main Profile? Yes, but only in its v11 version (the one that comes with WMP11). If you set the NumBFrames reg key, v11 codec will respect it for both Main and Advanced Profile.
fccHandler
8th July 2006, 23:04
Yes, main profile, but nope, I'm still using the old WME9 from a couple of years ago. (Help / About = version 9.00.00.2980.) Just to clarify, you're saying that this version will never insert B-frames if I'm using the Windows Media Video 9 codec?
zambelli
8th July 2006, 23:08
The encoder app version is irrelevant, as it's the codec DMO that does the actual encoding. WMV9 MP has been updated twice since its original release in v9. First time in WMP10, and second time in WMP11 beta. If you want to control B frames in WMV9 MP, you'll need the v11 beta version.
fccHandler
8th July 2006, 23:11
I see. My real goal is to figure out if some videos I encoded years ago might possibly have B-frames in them. I don't know an easy way to tell for sure. Thanks for your replies.
zambelli
8th July 2006, 23:34
I'm not aware of any public tools that would analyze a WMV/VC-1 bitstream and identify each frame by type. It certainly would be possible to make one though.

I'd say the likelihood of having B-frames in your old WMV9 encodes is fairly low.
bond
9th July 2006, 12:08
are there any tools that allow you to show whether a file uses b-frames (or any other stream properties)?

that would be really helpful
SeeMoreDigital
9th July 2006, 12:18
A tool with the functionality of MPEG4 Modifier for use WMV streams placed within WMV and AVI would most certainly be helpful ;)

Anybody interested?
crypto
9th July 2006, 15:05
are there any tools that allow you to show whether a file uses b-frames (or any other stream properties)?

that would be really helpful

You can use WMSnoop (http://www.sliq.com/?wmsnoop) for that. Although it is a rather old tool w/o support for AP you can detect B-frames from the typical frame size pattern. Here is a sample of 2 B-frames encoding with the new Windows Media Encoder Studio Edition

http://dvbportal.dyn1.de/forum/attachments/wmsnoop.jpg