Looking for help understanding Codec & Filters

[satwar]

In spite of all the reading I've done, I still feel confused about codecs & filters. I understand that Codecs are small programs that encode & decode audio/video with a specific format. But where are these programs stored and how do software audio/video players use them.

Windows media player seems to know how to play an MP3 but not a DVD (mpeg-2). Presumably I need to install an mpeg-2 codec but what one to install? Will any of one of the following do: YMPEG, Stinkys MPEG2 Codec, NVIDA PureVideo Decoder, ffdshow (or is this just a filter)?

I have Cyberlink DVD player installed which does play DVDs and has it's own plugins for mpeg-4 files. Am I correct in assuming that Windows Media Player does not have access to this plugin and requires a mpeg-4 codec to be installed? How does Windows Media Player find the required codec?

When I installed Virtualdub, I had to install AC3 ACM decompressor so that Virtualdub could understand AC3. Is this decompressor only available to Virtualdub or can Windows Media Player access if required?

What is the difference between AC3 ACM and AC3 Filter? How does a Filter function differently from a Decoder, since they both seem to function as decompressors?

What do the terms DirectShow and ACM refer to?


Thanks in advance for your time.

[satwar]

Hey Guys,

Have I posted in the wrong section, or are my questions too silly to be answered? I formed these questions as I worked through some of the conversion tutorials, many of which are heavy on what steps to take but light on why they're being done.

I'm sure some of you can throw me a few bones or references. I'm really trying to understand why I'm doing things not just how to do them.

[redwudz]

Windows tries to hide the codecs. If you go to Control Panel>Sounds and Audio Devices>Hardware you will see the lists of audio and video codecs on your system. Double click on 'Video Codecs' and select Properties and that is what is available to Windows. You can do the same with Audio Codecs. Some may be in other locations. I guess it depends on the program that uses them.

Windows comes without a MPEG-2 Codec, apparently because of copyright issues. If you have a software DVD player such as Power DVD installed, your other programs should be able to use it's codec, even if you uninstall the player program. Stinky's MPEG-2 codec will work also.

FFDSHOW will work also, but it's used more commonly for Xvid, Divx and other forms of AVI.

I'll let someone else answer about AC3 and directshow. If not, do a Google search for those terms.

BTW, 'standard' procedure for codecs is to use a program such as Gspot or AVIcodec on an unplayable file to determine which codec is needed. Stay away from codec packs as they often cause conflicts. Identify the codec you need and install only that. There are no universal codec solutions.

[edDV]

...
Windows comes without a MPEG-2 Codec, apparently because of copyright issues.
...

I'll let someone else answer about AC3 and directshow. If not, do a Google search for those terms.

The issue with Windows and MPeg2 is MS didn't want to build a MPeg2 royalty into the cost of Windows OS. If you install a licensed MPeg2 codec from another program (e.g. PowerDVD, WinDVD) then WMP will use it to play DVDs.

AC3 decoders and encoders need separate royalty payments and carry more restrictive licensing terms. I suspect they aren't shared as much by programs due to licensing restrictions but I haven't researched this in detail.

DirectShow is the part of DirectX that manages media import, export and display.

Satwar, make your questions more specific and you will get more specific answers.

[satwar]

Excellent replies people, thanks very much. I guess I could have worded my questions better if I understood more, sort of a Catch 22 situation.

I'm still confused about ACM (Audio Compression Management) and DirectShow. Both seem to be different subsytems that Windows can use for handling audio. For instance, I can decode AC3 through the ACM substem by installing AC3 ACM Decompressor, or I can decode AC3 with a DirectShow AC3 Filter. They seem to be two different methods of getting AC3 decoded.

Am I even warm, or totally out to lunch? Do both methods enable Windows Media Player to play AC3?