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Codecs

by Steve Kerrison on 15 August 2005, 00:00

Tags: 3Com

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Hardware or software?

Codecs can be implemented in hardware or software. Software-based codecs are flexible because they can easily be updated, but they can use a lot of processing power, especially for encoding. In the early days of DVD movies, few computers were powerful enough to decode the data coming off a DVD, resulting in choppy images. Back then, there was a significant market for PCI cards that decoded MPEG-2 in hardware but this has largely faded away as PCs have become more powerful. Even so, since hardware-based MPEG-2 codecs free up the CPU for other tasks, they remain useful for editing MPEG-2 footage and are common in higher-end editing systems.

High definition video also puts the performance of software-based codecs under scrutiny. Playing WMV HD files eats up a massive amount of CPU time – especially the highest resolution 1080 footage, which can't be handled by anything but bleeding-edge PCs. As a result, hardware is coming to the rescue again. NVIDIA's range of GeForce 6 (and higher) graphics cards feature Pure Video technology, incorporating hardware-based acceleration of WMV HD decoding. And ATI, it may surprise you to know, is so well versed in the handling of HD footage that it supplies a huge proportion of the HD-decoding chippery in HD-compatible TV sets and projections systems.

Most of the codecs we've talked about are thought of as being PC-based but many are starting to move off the desktop – some into personal player devices such as those in the Apple iPod and Creative Zen ranges, and others into the living room. A number of set-top DVD players can already handle DivX and XviD files, others are at home with WMA and MP3 audio and JPEG stills, and some can even play back WMV HD. A select few can handle all these types of media and more.

You might also be surprised at the wide range of dedicated media players that already exists for use with TV sets and AV systems. Some connect to a home network and relying on being fed from PCs. Others are standalone and carry media on their own hard disk drives. The support provided by living-room player hardware will continue to broaden as new codecs gain in popularity.

Where PCs still have the edge, though, is in their ability to instantly adapt to the arrival of new codecs. Downloading new player software or a plug-in for an existing player will often do the trick – and that's worth remembering if you come across media files that don't play.

Life isn't so easy with DVD players or dedicated media players, whether portable or housebound. Their capabilities can sometimes be extended with firmware updates. But, typically, if these do arrive, they turn up long after PC users have gotten used to taking advantage of the new codec.

Thoughts

We've only scratched the surface of the world of codecs and containers. Perhaps, though, we've helped lessen some of the confusion you might have felt and made it clear that when you next purchase a DVD or media player, it's important to know what codecs are supported – to ensure it will play the content you own or intend to start using.

Hopefully, we've also opened your eyes just a little to the exciting possibilities that codecs have created and promise for the future. Compression techniques continue to improve in their efficiency and subtly - to meet the demand for higher-quality audio and video coming at us over limited bandwidth or on media with relatively limited capacities. The future is bright. The future is codecs.



HEXUS Forums :: 3 Comments

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A well written article however there are some current developments in progress that enthusiasts might be aware of:

Audio:

- HE-AAC v2 (High Efficiency AAC) is an extension of AAC for low bitrates (generally around 64kbps) which improves upon standard AAC by using a technique called Spectral Band Replication (SBR) which is (in simple terms) a shaped noise generation technique for higher frequencies which we are less sensitive to hearing.

With HE-AAC v2, it also uses Parametric Stereo (PS) which, instead of storing left and right channels independantly, encodes a mono signal and has stereo imaging information which constructs a reasonable trade-off for stereo encoding.

Video:

- There are a number of new codecs being worked on, mostly based around h.264 - the latest technology for video compression worked on by MPEG.

You can expect to see a lot more h.264 video downloads in the future.

The reasoning is this: Xvid, DivX, current generation WMV and 3ivX are pretty much all based upon Mpeg-4 Advanced Simple Profile - which is basically a method of compressing video by using various coding techniques combined.

H.264 is the newest compression standard, also known as Mpeg-4 Advanced Video Compression - which is significantly better and already a standard in use. HD-DVD and Blu-Ray are going to base their video format on H.264/AVC. If you have a Sony PSP, the video on there is H.264/AVC - and it's currently usable in software form with QuickTime 7, NeroDigital or the heavily in development x264 (which is making great progress).

- The lesser used VP4/5/6/7 codecs created by On2 are most likely to be encountered when using WinAMP and watching Nullsoft Video streams. It's not the most robust streaming technology and has a limited audience however it's a good demonstration of VP video codecs. (as an aside, Ogg Theora is based upon VP3 - On2 had open sourced the codec and licensed it for public domain usage with all patents encompassing).

To learn more about all this technology you can visit www.doom9.org for Video and www.hydrogenaudio.org for Audio.

Hope this has been informative! ;)

Ruairi
I had to do a talk and presentation on codecs in the first week of my AS computing course, its a subject close to my heart.
Nice bit of extra insight there rc55. That's why I love the HEXUS.community :)