HEXUS.guide: Codecs

[Steve]

CoDecs compress and decompress data. The word CoDec is a shortening of the term Compressor/Decompressor. Compressing a data stream or a file reduces its data rate. This cuts costs all the way down the line. It reduces the bandwidth required for transmission or broadcasting and the amount of space required for storage. Before the data can be used, though, it has to be decompressed. Both phases of a CoDec's work can be carried out in hardware, in software or a combination of both.

Heducate me baby...

[rc55]

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

[Scarlet Infidel]

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.

[Steve]

Nice bit of extra insight there rc55. That's why I love the HEXUS.community