While filming a wedding recently, I filled up a couple of 60-minute, miniDV tapes recording the ceremony and other festivities. The video was then transferred to the computer in order to create a DVD that could be sent out to the wedding party and other guests. Care to venture a guess as to how large the raw video from the miniDV tapes was? It was almost 26 GB! That's roughly 40 standard CD-ROMs or four DVD ROMs. As a raw file, the video would be much too large. This is why codecs were created.
A codec (from COmpressor/DECompressor) is a piece of software that takes a stream of raw information and compresses it into a file suitable in size for computer playback. Codecs were created in the early 1980s to help solve the issue of storage and transmission of raw video and/or audio.
Once the video (or audio) is compressed, the same codec used to compress it must be present to decompress it during playback.
Today, there are literally thousands of different codecs available. Codecs like MPEG and Sorenson are somewhat generalized, but there are also codecs made specifically for music, screen capture, spoken voice, and more.
So how do you know which codec to use to compress a video? And how do you know someone watching the video will have the same one? There is no simple answer. Some codecs work better for certain things (animation versus live action for instance), and the decision will ultimately depend on you, and your intended audience.
Microsoft and Apple have made things easier by having their players support many different codecs. QuickTime, for example, which runs on both Macintosh and Windows platforms, supports some 25 video and 15 audio codecs. The older AVI format created by Microsoft, as well as the newer WMV & WMA (Windows Media Video & Audio) formats work in much the same manner, and can even download new codecs as needed from the Internet.
Essentially, it comes down to which platforms you'll be supporting (Macintosh or Windows, or both) and what codec works well for what you're compressing. Currently, many developers choose to use QuickTime's MOV format because it's supported on both Windows and Macintosh and offers a wide range of codecs, as mentioned previously. Both Sorenson and MPEG provide very high-quality results and are both supported by QuickTime. Another plus in QuickTime's favor is that it is very precise, timing-wise. Telling a QuickTime movie to jump to a specific location with Lingo works flawlessly, while telling an AVI to do the same may get you close, but rarely exactly where you want to be.
The newer Windows Media Video format, supported by the Windows Media Player, also provides visually superior results, but when used within Director it only works in Windows. QuickTime then, might seem an obvious choice to use, because it's cross platform, but there is still a downside. It doesn't come as a standard part of Windowsit's made by Apple, after all. And while it is quite common for people to have it already installed, you as the developer can't assume that it will be available. The solution many developers use is to simply include the QuickTime installer on their CDs so the end user can install it before running the Director movie. However, having end users install software doesn't sit well with all developers. Many end users can do little more than type email and move the mouse around. So what can you do to insure your video will be seen?