In-Depth Look At Video Codecs

johnsee writes "Atomicmpc has an incredibly in- depth look at a wide range of video codecs. It looks not only at their inner workings, but also shows the quality produced by each at a variety of settings and situations."

Comments

Uncompressed Codecs

[Doc Ruby]

The article makes some serious errors in overgeneralizations. It says that all codecs have in common that they make bitstreams shorter for transmission. But not all codecs compress (or otherwise reduce) their data. Some codecs transmit uncompressed raw data, increased in size by adding encoding data. For example, HD video monitors connected by HDMI (or DVI) use TDMS encoding not for compression, but to increase reliability in transmitting large raw data streams (10.2Gbps) quickly enough (340MHz) over cheap HW.

And though humans learned stone tools remarkable close to finally learning to load CD-ROMs, the stone tools were paleolithic ("old stone"), while the CDs were at worst neolithic ("new stone"). Someday we'll look at the modern era as a new age, probably "hualic", or "glass" age. These silicon chips and glass fibers have changed us as much as we've changed the glass from which we make them.

Just for kicks, I note that we've encoded the Si atoms into the new tools that define our age.

In this case, don't RTFA

[Rui del-Negro]

I've just read a bit of the article and the only thing I can think of is to paraphrase Stanislaw Lem: "it always amazes me that people need a license to drive a car but can write and publish all sort of nonsense without any clue about the subject".

His descriptions of "temporal compression" and "motion compensation" (to name just two of the fundamental building blocks of modern video codecs) are so wrong they don't even qualify as an error. He confused delta compression with motion compensation, thinks MPEG1 lacked the latter, doesn't understand why the former is virtually useless for video... sigh... even trolled Wikipedia articles manage to be more accurate than that.

I feel truly sorry for the people who read that and think they've learned something about the subject.

Re:In this case, don't RTFA

[Rui del-Negro]

God, I've just read his description of DCT. It's even worse. He seems to think that DCT consists of "dividing numbers by two" (he doesn't even use the word "quantization", that probably has too many syllables). And people complain about Wikipedia...

Time to shamelessly plug my articles about compression. Some parts are simplified (they're aimed at "end users") but, compared to this Atomic article, anything is flawless:

Lossless (data, image, audio)
http://digitalproducer.digitalmedianet.com/article s/viewarticle.jsp?id=106309

Lossy + Hybrid (image, audio)
http://digitalproducer.digitalmedianet.com/article s/viewarticle.jsp?id=109739

Video (lossless, lossy)
http://digitalproducer.digitalmedianet.com/article s/viewarticle.jsp?id=125089

The description of DCT is pretty funny

[Hoplite3]

I'm a bit skeptical of information in that article after reading the DCT description that described it as a rounding trick. What, is frequency-space too hard of a concept? Doesn't everyone get some Fourier analysis in college these days? You need to know it to be informed about a lot of modern data analysis.

A wide range?

[jd]

I've seen more codecs on the back of a postage stamp. Seriously, one "modern", effectively one "old" (DivX and XviD are forks of the same original design), and one "archaic" does not make for much of a range. It doesn't even cover the spectrum of eras, never mind the spectrum of codecs.

For those who like laundry lists, here are some codecs not listed: Dirac, Theora, Huffyuv, Lempel-Ziv-Oberhumer Codec, MNG, Cell, NV, WaveCodec, Motion JPEG and MSU Lossless Video Codec. The wikipedia page doesn't list all of these, it took some scouting to find others and some of the early early ones are apparently only listed in the documentation on Open Source videoconferencing software I had back in the early 1990s.

Are any of these significant, though? Well, Dirac (BBC) damn well should be - we're only talking a high-definition TV quality codec by a major broadcaster with on-site offices in most countries that would be a logical choice for their remote bureaus to use and be a good candidate for competing with digital broadcasters in general.

Theora - well, it would be the ideal desktop videoconferencing codec in many ways. Those in common use today are heavier than necessary but the quality you buy with that at the bandwidth generally available just isn't worth it.

Huffyuv is said to be the fastest codec on the planet by some, which is entirely possible. That would make it good for most things where CPU power is expensive but bandwidth is cheap. (Embedded systems would probably fall into that category a lot.)

MSU's Lossless Codec is probably the slowest codec ever written, but gives by far the best compression. It makes a great reference codec to compare others against, apparently. If you could develop a decent hardware implementation, it might be a serious competitor to HD-DVD and Blu-Ray, as you could pack a comparable volume of material onto a standard DVD and therefore use already-existing commodity disks and players. All you'd need is a patch kit to add the decoder. This would likely appeal far more to consumers, as they wouldn't need to spend as much, but the studios and the manufacturers would hate and despise it for the same reason.