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ExtremeTech Wages War of the Codecs
prostoalex writes "ExtremeTech tested Windows Media, DivX, QuickTime/Sorenson and QuickTime/MPEG4 codecs. They encoded clips from Matrix Reloaded, Monsters, Inc., X2 and Spider-Man. QuickTime/Sorenson won the encoding speed contest, for the quality tests read the entire review, as each movie sample was encoded with 500KB and 1MB bitrates. Video samples provided on the site as well, so see for yourself."
Here's their most recent codec shootout with 3ivx, Divx, ffvfw, Nero, Real, On2 and Xvid. Xvid wins.
Whether they hide the first pass or not, you'll need two if you really want quality. It's the only way for the codec to know for sure where it can spare bits and where it can't.
Did you read the *whole* article? They state very plainly at the end that "DivX encoded clips tended to have a touch more detail, but also a few more compression artifacts, than the WMV9 video" and that DivX encodes much faster than WMV9. In brief, the only reason for choosing WMV9 over DivX is that it may be included in upcoming consumer devices.
Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws-Plato
One thing the article and most people here seem to miss is DivX *IS* MPEG4. XviD is as well - that's why a MPEG4 decoder like ffdshow can play them both.
The article can really give people the wrong idea - it's not the MPEG4 codec, but maybe Apple's implementation that's to blame. Perhaps it just doesn't support all of MPEG4's features. Then again, perhaps the people doing the review just didn't know how to set up the encoder properly. Regardless of codec, there's quite an art to good encoding.
Okay, so I AM the world's leading expert on video compression codecs and formats (no, really, I am). I cover the same ground in my book, and in a series of articles for DV magazine over the last five years. So I'm pretty picky on this kind of things. But these guys couldn't compress themselves out of a wet paper bag.
Some fundamental errors:
They're using MPEG-2 sources, which are already highly compressed (this has been amply covered by other posters).
They talk about converting to an "uncompressed" AVI, but never specify which flavor of uncompressed. They should have used a lossless codec that uses the native Y'CbCr color space of video, like Huffyuv. They way they just said "uncompressed" suggests they used the AVI "None" codec, which is uncompressed RGB. This causes two lossly color space conversions - one from the Y'CbCr of the source to RGB, and then back to Y'CbCr in the delivery codec.
They used Indeo 5.1 as their intermediate codec. This is terrible. Indeo uses what's called YUV-9 sampling. There is only one measurement of color per 4x4 block of pixels. This throws away 75% of the color information from the DVD (which uses 4:2:0 sampling, with 2x2 blocks), before it even touches a codec. And this results in very ugly blocks whenever there are highly saturated regions with sharp contrast. So, all the output is going to look highly compressed when rendered from these intermediates, even if further compression is lossless. Look at the Spider Man test frame for an example. Notice the red blooming around the shoulders of the vocalist. And the color everywhere is very muddled. Indeo can also be slow to decode, unless it was encoded with all keyframes. And how slow it is to decode will vary with the tool, which probably added measurable error to their encoding time measurements.
They don't know the difference between Sorenson Video 3, which comes free with QuickTime, and Sorenson Video 3.3 Professional, which you have to pay for and is what Apple uses for their movie trailers. With the Pro version, critical features like B-frames and 2-pass VBR are available.
Apple's MPEG-4 encoder isn't very good - 1-pass only, tuned for speed more than quality. A file with the exact same compatibility could be made with Squeeze, Compression Master, Envivio, etcetera with MUCH better quality. And the Divx MPEG-4 codec is, of course, also MPEG-4.
They didn't use 2-pass encoding! No quality-concious encoder would ever put content on spinning disc without using 2-pass. And they didn't mention most of the other encoding settings they used, which by context I'd guess were basic defaults.
That's from an initial skim. If I spent more time with the article.
In summary, these guys spent hours and hours analyzing the results of tests, where they would have been WAY better off spending an hour asking someone who knew anything about video compression how to administer this kind of test.
Oddly enough, their results are vaguely like you'd expect - WMV9 and DivX do well, Sorenson less so, and Apple MPEG-4 at the rear. Done properly, I imagine WMV9 would have had a slight lead, and Sorenson 3 Pro would have been a lot closer to DivX. And no one uses Apple's MPEG-4 codec for content distribution. QuickTime's decoder is fine, so folks would use a professional-grade MPEG-4 encoder instead.
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