Software capture question/ comparison /codecs

[neftv]

Has anyone anyone compared between Nero Vision 4 (part of Nero 7) and Main Concept PVR as simply capturing analog video and audio?
I wonder how does Windows Xp know which codecs to use when encoding and decoding MPEG2? can it get messy if one has to many applications on a PC?
Thanks.

[redwudz]

It could get 'messy', but Windows sets priorities for codecs. If one has a higher priority, then it will get used first. You can use a program like Gspot 2.60 and it can tell you which version or codec is being used. At the bottom of Gspot, you will see the 'Proposed Codec Solutions and Tests'. Click on the highlighted boxes and it will tell you what is used by the OS to 'render' the video format. It works for audio also.

[neftv]

I think windows does an unremarkable job of managing codecs. I have a system that has Ulead software, Mpeg wizard, roxio and when I play each media captured by the software mentioned in windows media player and click on properties it shows different codec for each file made and different for audio and video too.

[Ruut]

Hi redwudz,

I checked out Gspot as you suggested to neftv. I'm getting a list of possible codecs: some are green and others are red. Is there any way the priority can be altered?

[JohnnyMalaria]

I think windows does an unremarkable job of managing codecs. I have a system that has Ulead software, Mpeg wizard, roxio and when I play each media captured by the software mentioned in windows media player and click on properties it shows different codec for each file made and different for audio and video too.

It isn't Windows' fault.

There are two technologies of codecs used and, for each, applications can choose two ways of selecting which one to use.

Video for Windows (VfW) Codecs

These are the old technology. VfW has been around since Windows 3.1 and Microsoft wishes developers would stop using it. One of the problems with it is that for any given video format (e.g., DV, MJPG, DIVX etc), there can be only one codec installed. By installed, I mean registered with the OS in such a way that applications can simply request a codec for a given format and the OS will find it. Furthermore, the way that a codec advertises its format is via the FourCC code - a four-character string such as 'dvsd' for DV, 'mjpg' for MPJG etc. This severely limits the number of formats that can be supported and requires that the FourCC code be registered with (I think) Microsoft so that the same code doesn't get used for more than one format. Fina illy, both the encoder and decoder function have to paired together in the same "driver". i.e., you can't use Company X's DV encoder and Company Y's DV decoder. (Well, you can, but it requires some special programming).

DirectShow Codecs

Formerly known as ActiveMovie and part of DirectX technology, DirectShow is a much more versatile technology.

More than one codec for a given format can be registered with the OS. A priority is assigned (usually by the codec developer) to assist the OS in choosing which one to offer up when asked.

The encoder and decoder are separate. They can exist in the same file but, from a logical view, they are still separate. This permits using Company X's encoder and Company Y's decoder.

They aren't limited to the FourCC format description. They use a "Global Unique Identifier" or GUID (a 128-bit number).

OS versus Application Selection

This applies to both VfW and DirectShow codecs.

Typically, an application will rely on the OS to locate the right codec to process a given format. VfW and DirectShow have different mechanisms to do it but the end effect is that the application doesn't need to know where the codec is located or anything else about it.

Alternatively, an application can choose a specific implementation of a codec without the OS's help. For example, Company X may have an MPEG2 decoder that has certain extra features and they want to guarantee that their decoder is used in their software and that it isn't available to other software. Their software will simply go straight to the decoder.

[edDV]

Alternatively, an application can choose a specific implementation of a codec without the OS's help. For example, Company X may have an MPEG2 decoder that has certain extra features and they want to guarantee that their decoder is used in their software and that it isn't available to other software. Their software will simply go straight to the decoder.

So is this how VLC uses a set of codecs that don't seem to be available to other applications? Are they decoding separately from Windows?

Also, is there any way to trace which application installed a particular codec under VFW or DirectShow?

[JohnnyMalaria]

So is this how VLC uses a set of codecs that don't seem to be available to other applications? Are they decoding separately from Windows?

It could be. One way to tell is to look in its installation folder and see if there are files that would suggest they are codecs. The other possibility is that the codecs are hard-coded into the main application. e.g., if I write my own DirectShow codec for something, instead of making it a separate file that any other application could use, I can make it a part of the main application (the .exe file). Internally, the application will use that part of the code just as if it were a separate, standalone DirectShow filter file.

Also, is there any way to trace which application installed a particular codec under VFW or DirectShow?

Typically, DirectShow codecs are installed in the same folder (or a subfolder thereof) as the main application. The OS's registry contains information about where the codecs are installed and that would provide a clue.

VfW codecs historically get put in system32. If you can find the dll file then you can check its properties to get the vendor info.

Of course, this isn't much help for third-party codecs. e.g., MyWizBangApp comes with TheirSoopaDoopaCodec. You can't tell that it was MyWizBangApp that installed the codec.

Well, you can tell if you are prepared to do some serious digging. If the application is installed by Windows Installer (msiexec) or compatible installers (InstallShield etc), the uninstall information will have the tell-tale signs. But you have to locate the uninstall information (via registry hunt) and then have the right tools to decipher it.

Alternatively, if you are concerned about what installs what, you can make Windows create a very detailed log for every install that you do. You end up with a (usually) 1+ MB log file that is in plain text format. Buried within the hundreds of lines of text will be the information.

In theory, if you enable this kind of logging just after a clean OS install, you will end up with a lot of installer log files that you can then search using the humble Windows search. e.g., if you wanted to know how codec X got installed and you know that the codec's dll is x.dll, you just search all the logs for 'x.dll'.

[edDV]

Thanks. Great info.

[neftv]

So it sounds to me, being told that I have to watch out that a particular MPEG edit software might interfere with a particular encoding software that uses MPEG Encoder from Main Concept is not true than right? I was lead to believe that the codecs could conflict between to different manufacturers of software. Your saying the the choice of codec is driven by the application calling for the approprate one, correct?

I think windows does an unremarkable job of managing codecs. I have a system that has Ulead software, Mpeg wizard, roxio and when I play each media captured by the software mentioned in windows media player and click on properties it shows different codec for each file made and different for audio and video too.

It isn't Windows' fault.

There are two technologies of codecs used and, for each, applications can choose two ways of selecting which one to use.

Video for Windows (VfW) Codecs

These are the old technology. VfW has been around since Windows 3.1 and Microsoft wishes developers would stop using it. One of the problems with it is that for any given video format (e.g., DV, MJPG, DIVX etc), there can be only one codec installed. By installed, I mean registered with the OS in such a way that applications can simply request a codec for a given format and the OS will find it. Furthermore, the way that a codec advertises its format is via the FourCC code - a four-character string such as 'dvsd' for DV, 'mjpg' for MPJG etc. This severely limits the number of formats that can be supported and requires that the FourCC code be registered with (I think) Microsoft so that the same code doesn't get used for more than one format. Fina illy, both the encoder and decoder function have to paired together in the same "driver". i.e., you can't use Company X's DV encoder and Company Y's DV decoder. (Well, you can, but it requires some special programming).

DirectShow Codecs

Formerly known as ActiveMovie and part of DirectX technology, DirectShow is a much more versatile technology.

More than one codec for a given format can be registered with the OS. A priority is assigned (usually by the codec developer) to assist the OS in choosing which one to offer up when asked.

The encoder and decoder are separate. They can exist in the same file but, from a logical view, they are still separate. This permits using Company X's encoder and Company Y's decoder.

They aren't limited to the FourCC format description. They use a "Global Unique Identifier" or GUID (a 128-bit number).

OS versus Application Selection

This applies to both VfW and DirectShow codecs.

Typically, an application will rely on the OS to locate the right codec to process a given format. VfW and DirectShow have different mechanisms to do it but the end effect is that the application doesn't need to know where the codec is located or anything else about it.

Alternatively, an application can choose a specific implementation of a codec without the OS's help. For example, Company X may have an MPEG2 decoder that has certain extra features and they want to guarantee that their decoder is used in their software and that it isn't available to other software. Their software will simply go straight to the decoder.