Guide to Codecs

CODEC, it means COmpressor-DECompressor, it is a method used to compress and decompress video and/or audio data to produce files that are smaller, so that they are easier to distribute, and manage. CODECs control the video settings like frame rate, resolution, the amount of data that is used to encode each second of video/audio (bit rate) The CODEC, and the way it is used can dramatically affect the final playback quality of your files. Your choice of CODEC will also determine file compatibility and how large your file will be.

Most CODECs are lossy, which means they throw away parts of the original data in order to reduce file size. The CODEC will try to only remove data that people are not likely to notice, but if you set the bitrate too low for the resolution or amount of motion in your file, the CODEC will be forced to lose data that WILL be easily perceived by the watcher, in most Video CODECs this causes symptoms such as pixel “Blocky-ness”, dropped frames, causing jerkiness, in Audio CODECs a bitrate set too low it usually results in an audible hiss, making the sound much less dynamic, or making it sound “tinny”.

There is a tradeoff to be made when using a CODEC, quality versus file size – and some CODECs are better suited to some kinds of video than others.
Below is a basic rundown of some of the more commonly found CODECs, and their strengths and failings…

AVI and Quicktime – are, strictly speaking NOT CODECs, they are simply file formats, a “shell” that contains other audio and video CODECs In the past the most common CODECs used with AVI and Quicktime were the Cinepak and Intel Indeo. I would recommend neither of these, as they’re old, unsophisticated and do not offer very good quality or compression.

MPEG 1 - One of the most common video CODECs know to the digital world, and as such can be played back on just about any computer in use today, It offers quite good video quality, but creates files with large sizes. It’s most common use these days is for VCD’s. It usually uses MPEG Layer 2 Audio, which isn’t as efficient as other audio CODECs It’s not a good choice for online distribution because of the large file sizes.

MPEG 2 - is similar to MPEG 1 in that it offers excellent video quality. But was designed to support high resolution, high bitrate videos. DVD’s use the MPEG 2 format. And this should be your first clue as to the quality, but large file sizes this CODEC is capable of. As with MPEG-1, it’s good to archive your work in a high quality file, but not a good choice for online distribution.

ASF – “Advanced Streaming Format” is Microsoft’s ‘Streaming’ format based around the MPEG 2 format. The quality is not as good as it’s MPEG heritage suggests, but it does offer a much better file size to quality ratio. The CODEC had good specs on paper, but unfortunately, this CODEC can have serious synchronization problems on older PC’s or even the newest Macintoshes, where the video and audio slide out of synch with each other.

Sorenson Video – Most commonly used in Quicktime .mov files. It produces a higher quality video at lower bitrates than some other formats. You can choose whether or not you’d like the encoder to drop frames when the action gets too intense in a video, not quite as good as the variable framerate in MPEG 4 and Realmedia, but still useful for keeping the file sizes down (if you don’t mind some choppy-ness) When encoding a video, Sorenson converts the input format to the YUV9 color space. This negatively affects the quality prevents accurate retention of the original color information.

Real MediaReal Media is designed as a streaming format, but also makes a very good “download than play” choice. Also based around MPEG 2 formats, but unlike Like ASF, it is a much better implementation. it can be a bit processor hungry depending on the bitrate and resolution chosen, but for the large part most systems won’t have any issues. It offers very good video quality and it’s audio quality is surprisingly good even at low bitrates that would render an MP3 almost un-listanable. Real offers a ‘free’ encoder (as well as a free player), but to get full encoder which has expanded functionality and more control, you have to pay. And you’ll have to have your eyes sharply peeled to spot the links to the free versions on their website, as they try to hide ‘sm to get you to pay… sneeky bastards.
This format also excels at animation, because It is especially good at keeping regions of solid colors and sharp edges separate, which are commonly found in cartoons, and brickfilms. It also has a variable frame rate, which is fantastic for brickfilms as the nature of stopmotion means there are often areas where decreasing the video framerate will have no impact on the quality, or smoothness of the animation, it saves file size in low motion scenes, but it can also create choppy video in high motion scenes IF the bitrate is not high enough, so thought care is needed when selecting the bitrate.

MPEG 4 CODECs – MPEG 4 is the newest addition to the MPEG family. Basically It does the same thing for video that MP3 does for audio.It uses a *very* complex algorithm to compress and decompress video.Because it is so complex, MPEG 4 is also quite processor intensive.MPEG 4 is quickly becoming a very popular CODEC for online distribution,as it can offer one of the the highest quality to file size ratios available.
There are quite a few different MPEG 4 based CODECs available. The best known are Microsoft’s Windows Media Video (WMV included with the latest versions of windows media player) and Divx, and recently MP4 used in Quicktime files.
Like Real Media MPEG-4 has the ability to use a variable frame rate, and as such has the same pros and cons associated with this. And while a better performer with “live action” than Real Media, in my experience, it’s often the case where Real Media will outperform a DIVX file, for file size at equivalent quality, when encoding Brickfilms, but it’s a close call even then.

The verdict? – go with Divx or Realmedia, both are very good at what they do, both are cross platform CODECs (available for PC, Mac, and Linux users, the the vast majority of operating systems in use.), And both have significant benefits for Brickfilmers.
Most of the Codecs mentioned here, and many more can be found here.