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Real & WM9 Question

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Chuck Weatherall
Real & WM9 Question
on Apr 13, 2005 at 9:57:33 pm

I'm putting together a small report for my department on streaming technologies. We mainly use Macs and I'm fairly familiar with QuickTime. My question about Real and WindowsMedia9 is "Do they use intra-frame compression (ie, M-JPEG) or inter-frame (ie, MPEG)?" Thanks.

"Wherever you go, there you are."


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Bob Hudson
Re: Real & WM9 Question
on Apr 14, 2005 at 4:32:19 am

I have read that Real 8 and Real G2 are loosely based on Intel's Indeo Video Interactive (IVI) interframe codec, but Real has done so much development work since the 90's that who knows what's under the hood now.

Bob Hudson
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Video, DVD and
Multimedia Production
Overland Park, Kansas USA
http://www.bobhudson.com/


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Ben Waggoner
Re: Real & WM9 Question
on Apr 15, 2005 at 2:55:29 pm

Well, we certainly know that they use interframe compression. ALL significant delivery codecs (as opposed to content for video content authoring, like DV) use interframe compression, since it provides massive improvements in compression efficiency. It's been nearly a decade since any web content used intraframe (pre Sorenson Video QuickTime would use Photo-JPEG back around QT 2.5 and Movie Cleaner Pro 1.2). Oh, and maybe some pre v6 Flash video that also used JPEG.

An easy way to detect this is whether a codec offers a keyframe setting. Intraframe encoding only uses keyframes, so don't have a way to say how often to use them.

A somewhat more interesting question is which modern codecs use Bidirectional Prediction, where a frame can reference a frame in the future, as opposed to only frames in the past.


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Craig Seeman
Re: Real & WM9 Question
on Apr 16, 2005 at 6:00:18 pm

So Ben,

I'll ask something related to the "interesting question," what do you think about WMV's use of B frames and a Compressionist's control over this setting?


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Ben Waggoner
Re: Real & WM9 Question
on Apr 16, 2005 at 6:34:13 pm

B-frames are a good thing. They improve compression efficiency, and offer a useful, simple scalability mode.

I don't know why most WMV tools don't over a control over them. The only one I know of that does is Compression Master.


My Book: http://www.benwaggoner.com/books.htm
Squeeze and ProCoder tutorials: http://www.classondemand.net/benwaggoner/
Compression Class at Stanford: http://www.digitalmediaacademy.org/compression.html


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Craig Seeman
Re: Real & WM9 Question
on Apr 18, 2005 at 12:20:09 pm

[Ben Waggoner] "The only one I know of that does is Compression Master. "

Question I have is why wouldn't one want B frames tied directly to key frames since they contain most complete "picture?"


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