DirectShow is Microsoft Windows' underlying multimedia framework. Windows calls on DirectShow to do things like play video and audio. Most people assume computers now play any type of video or audio right out of the box. However we deal with so many types of video we know that's not the case.
We recently had a call from someone new to the world of video evidence. They understood AVI to be a standard video format. It's not. That's right. If you didn't realize it, AVI is a standard file container not a standard video file format.
Here is the shake down on AVI.
Being a standard file container means that an AVI file can be opened by any program that works with the AVI format. Let's use Windows Media Player. WMP opens an AVI and looks at the video contained in the file to determine its type of compression. If can play that type of video: it does. And if it can't? It throws you a not-at-all-useful error message.
How do we cope? We need CODECS, the cure all for opening a compressed video file. Once Windows Media Player determines the type of video in the AVI file it then looks for the matching CODEC on your computer. You can think of CODECS as keys that allow your computer to unlock various types of compressed video. Each type of compressed video requires its own key. And just like my key ring is different from your key ring so is each computer's key ring of CODECS. My computer may have different CODECS than your computer, which explains why the AVI file the detective claimed wouldn't play (on his computer) played with no problems on your StarWitness computer. There are more CODECS loaded onto our StarWitness systems than the typical office computer.
No matter how cool, new, high-tech or video-enabled your computer is, you'll still run into a video you can't play. You'll know you don't have the right CODEC when you get that not-at-all-useful error message from Windows Media Player. What to do? Get a CODEC Appliance. (It's a fancy name for free software. One CODEC Appliance is GSpot. Once again, I didn't say it, or name, it in this case.) When you open an AVI file in GSpot you'll get the name of the CODEC. Then you can google to find a free download. Once you install the downloaded CODEC, the video should play.
Should doesn't mean always will.
CODEC woes don't always end with a simple install and download. If you work with CODECS long enough you'll see some "strange behaviors". (Not just your own strange behaviors: strange behaviors of your computer.) These could be a video opening in one program, such as Windows Media Player, but not opening in another, such as importing into Freezeframe. Or reinstalling a video CODEC, which you know had previously worked fine on your system, and discovering it is haywire the second time around. Even the experienced, technically savvy and computer nerdiest among us just want CODECS to go away sometimes. Many times these deeper CODEC issues involve something so dear to Windows' heart: the Windows Registry. If you end up stuck with a serious CODEC issue you may need help repairing your Windows Registry. Give us a call 1-877-674-3031.
And now you have background knowledge for understanding Wikipedia's explaination of CODEC hell, or at least you should enjoy the fact that "nuclear arms race" is used in the description.
"Codec hell (a term derived from DLL hell) is when multiple DirectShow filters conflict for performing the same task. A large number of companies now develop codecs in the form of DirectShow filters, resulting in the presence of several filters that can decode the same media type. This issue is further exacerbated by DirectShow's merit system, where filter implementations end up competing with one another by registering themselves with increasingly elevated priority.
"Microsoft's Ted Youmans explained that '[DirectShow] was based on the merit system, with the idea being that, using a combination of the filter’s merit and how specific the media type/sub type is, one could reasonably pick the right codec every time. It wasn't really designed for a competing merit nuclear arms race.'
"A tool to help in the troubleshooting of "codec hell" issues usually referenced is the GSpot Codec Information Appliance, which can be useful in determining what codec is used to render video files in AVI and other containers. GraphEdit can also help understanding the sequence of filters that DirectShow is using to render the media file. Codec hell can be resolved by manually building filter graphs, using a media player that supports ignoring or overriding filter merits, or by using a filter manager that changes filter merits in the Windows Registry."
There is hope. Some market surveys paint a picture of a future with fewer compression standards in use by the surveillance industry. But for now we have to deal with all of them odd-balls as many as they are.
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