vfw-wdm confusion

maxwell3 · 24th April 2004, 13:33

It seems the more I read the more confused I get . Is win xp vfw or wdm ? I think its wdm but then why when I start iu vcr and choose encoder does huffy say vfw(as do others) next to it . Do I need the vfw-wdm wrapper? Im going to try to capture vhs tapes using iuvcr virtualvcr or flyds . Id like to use flyds but cant find a guide .Lastly can someone tell me what chip MSI tv@nywhere uses and should I use different drivers btwin etc.. anyway please help if you can Thanks

Arachnotron · 24th April 2004, 15:55

Below is my understanding of this. It may or may not be correct.

vfw is the older 16 bit multimedia API developed for windows 3.1. When 32 bit's applications became possible and new multimedia possibilities reached the PC world a new API was needed. Also, vfw had only basic capping capabilities and had no suport for controling a TV tuner. This was added on by card manufacturers, but each made it's own implementation and there was no standardized way to do it. This gave rise to many TV apps that only worked with one specific TV card.

The new API was developed under the code name Quartz, a name you can still find traces of. It was released as an add-on for Windows 95 though at the time it was called ActiveMovie. It could do more and work with more devices than the old one and it was modular. These modules are known as directshow filters and could be stringed together in many ways to create filter chains.

In 1996 Microsoft renamed ActiveMovie to Directshow. In 2000, directshow - which by that time included DVD support- stopped being a separate add-on and was integrated into DirectX 8. However, the VFW API is still present in Windows and applications using the vfw api continue to work, which is why you can still find vfw codecs.

WDM stands for the Windows Drivers Model. It was introduced in Windows 98 as the successor to the previous VXD drivers. All 98 flavours accepted both. But beginning with windows 2000 and windows XP only WDM drivers are supported. The link with vfw is that WDM drivers can only be accessed through the DirectShow API and cannot be accessed directly through the vfw api.

As a result, a wrapper is needed to interface between applications using the vfw api and WDM drivers. This wrapper is included in XP so you don't have to install it. Though vfw capable drivers are still possible under w2k/xp, almost no manufacturer will bother with them. Mostly they will be converted older NT 4.0 drivers that are used for legavy devices.

The reality however is that many WDM driver function only partially or not at all when accessed through the vfw wrapper. This is why so many people have problems getting vdub to cap. Also, since the vfw api is much more limited then the directshow one, you will find that some of the device settings cannot be set or reached from within a pure vfw application.

An directshow application like AMcap, FlyDS or VirtualVCR will go directly to the WDM drivers and does not need the wrapper. Your chances of getting one of those working are much higher. If you have troubles capping with vdub, start out with a basic directshow app like AMCap to make sure the hardware part is functioning. Only when that works, start troubleshooting vdub.

The MSI tv@nywhere TV cards use a CX23881 or CX23883 depending on the country. The BTWincap drivers do NOT work with this chip, they are only for their BT87x predecessors. AFAIK there are no alternative drivers for the CX2388x yet.

[edit]
The first release of windows 98, though officially already supporting wdm drivers, still had some problems with it and changes were made in Windows 98 SE. As a result, WDM drivers for win98 SE and win ME do not work in the first edition of win98. Only a few manufacturers bothered to create two sets of windows 98 wdm drivers, in most cases you simply have to take the windows 95 driver versions if you are running windows 98.

bb · 24th April 2004, 17:46

bb

maxwell3 · 24th April 2004, 18:55

Thank you...Any idea why fly ds , when choosing an encoder such as huffy, mjpeg etc shows vfw in front of them

Arachnotron · 25th April 2004, 02:30

Most of the above was culled from MSDN when I was trying to understand the same things. But I'm not a programmer, so I can only provide you with my interpretation of what I think is going on here.

From msdn:

Quote:

DirectShow includes filters that support codecs written for the Audio Compression Manager (ACM) and Video Compression Manager (VCM) interfaces.

DirectShow enables applications to play files and streams from various sources, including local files and remote files on a network. DirectShow has native compressors and decompressors for some file formats, and many third-party hardware and software decoders are compatible with DirectShow. In addition, DirectShow supports legacy VfW codecs based on the Video Compression Manager (VCM) and Audio Compression Manager (ACM) interfaces. Playback makes full use of DirectDraw hardware acceleration and DirectSound capabilities when the hardware supports it.

So, you have codecs that were written for vfw but can still be accessed through DirectShow, and you have native DirectShow codecs.

I would imagine that the second kind cannot be used in a vfw application. Huffy and your MJPEG codec are vfw codecs and FlyDS tags them as such. I suppose some codecs might be available in both flavours, in which case you would want to pick the DirectShow version if it is available.

Writing codecs in vfw form has the advantage they can be used on any Windows platform and with any application.

WildCelt · 26th April 2004, 13:35

Given the information in this (excellent) explanation, why does vdub only use vfw? Why has no one re-written it for wdm?

Arachnotron · 26th April 2004, 14:09

See this and this thread on everwicked.

It looks like this is a non-trivial change. And there are plenty directshow capping applications out there so you can always cap with those and process the capped video in vdub afterwards

WildCelt · 26th April 2004, 14:29

Thanks for the info.

Yeah, I dumped vdub a while ago for raw capture. I get great results with VirtualVCR.

maxwell3 · 26th April 2004, 17:10

please check your pm Thanks

24th April 2004, 13:33	#1 \| Link
maxwell3 still learning Join Date: Nov 2002 Posts: 138	vfw-wdm confusion It seems the more I read the more confused I get . Is win xp vfw or wdm ? I think its wdm but then why when I start iu vcr and choose encoder does huffy say vfw(as do others) next to it . Do I need the vfw-wdm wrapper? Im going to try to capture vhs tapes using iuvcr virtualvcr or flyds . Id like to use flyds but cant find a guide .Lastly can someone tell me what chip MSI tv@nywhere uses and should I use different drivers btwin etc.. anyway please help if you can Thanks Last edited by maxwell3; 24th April 2004 at 13:39.

24th April 2004, 15:55	#2 \| Link
Arachnotron Alias fragger Join Date: Jul 2003 Location: the Netherlands Posts: 863	Below is my understanding of this. It may or may not be correct. vfw is the older 16 bit multimedia API developed for windows 3.1. When 32 bit's applications became possible and new multimedia possibilities reached the PC world a new API was needed. Also, vfw had only basic capping capabilities and had no suport for controling a TV tuner. This was added on by card manufacturers, but each made it's own implementation and there was no standardized way to do it. This gave rise to many TV apps that only worked with one specific TV card. The new API was developed under the code name Quartz, a name you can still find traces of. It was released as an add-on for Windows 95 though at the time it was called ActiveMovie. It could do more and work with more devices than the old one and it was modular. These modules are known as directshow filters and could be stringed together in many ways to create filter chains. In 1996 Microsoft renamed ActiveMovie to Directshow. In 2000, directshow - which by that time included DVD support- stopped being a separate add-on and was integrated into DirectX 8. However, the VFW API is still present in Windows and applications using the vfw api continue to work, which is why you can still find vfw codecs. WDM stands for the Windows Drivers Model. It was introduced in Windows 98 as the successor to the previous VXD drivers. All 98 flavours accepted both. But beginning with windows 2000 and windows XP only WDM drivers are supported. The link with vfw is that WDM drivers can only be accessed through the DirectShow API and cannot be accessed directly through the vfw api. As a result, a wrapper is needed to interface between applications using the vfw api and WDM drivers. This wrapper is included in XP so you don't have to install it. Though vfw capable drivers are still possible under w2k/xp, almost no manufacturer will bother with them. Mostly they will be converted older NT 4.0 drivers that are used for legavy devices. The reality however is that many WDM driver function only partially or not at all when accessed through the vfw wrapper. This is why so many people have problems getting vdub to cap. Also, since the vfw api is much more limited then the directshow one, you will find that some of the device settings cannot be set or reached from within a pure vfw application. An directshow application like AMcap, FlyDS or VirtualVCR will go directly to the WDM drivers and does not need the wrapper. Your chances of getting one of those working are much higher. If you have troubles capping with vdub, start out with a basic directshow app like AMCap to make sure the hardware part is functioning. Only when that works, start troubleshooting vdub. The MSI tv@nywhere TV cards use a CX23881 or CX23883 depending on the country. The BTWincap drivers do NOT work with this chip, they are only for their BT87x predecessors. AFAIK there are no alternative drivers for the CX2388x yet. [edit] The first release of windows 98, though officially already supporting wdm drivers, still had some problems with it and changes were made in Windows 98 SE. As a result, WDM drivers for win98 SE and win ME do not work in the first edition of win98. Only a few manufacturers bothered to create two sets of windows 98 wdm drivers, in most cases you simply have to take the windows 95 driver versions if you are running windows 98. Last edited by Arachnotron; 25th September 2004 at 12:14.

24th April 2004, 18:55	#4 \| Link
maxwell3 still learning Join Date: Nov 2002 Posts: 138	Thank you...Any idea why fly ds , when choosing an encoder such as huffy, mjpeg etc shows vfw in front of them Last edited by maxwell3; 24th April 2004 at 18:57.

26th April 2004, 17:10	#9 \| Link
maxwell3 still learning Join Date: Nov 2002 Posts: 138	please check your pm Thanks Last edited by maxwell3; 26th April 2004 at 17:12.

24th April 2004, 17:46	#3 \| Link
bb Moderator Join Date: Oct 2001 Location: Germany Posts: 2,665	bb

26th April 2004, 13:35	#6 \| Link
WildCelt Registered User Join Date: Sep 2002 Location: Michigan Posts: 91	Given the information in this (excellent) explanation, why does vdub only use vfw? Why has no one re-written it for wdm?

26th April 2004, 14:09	#7 \| Link
Arachnotron Alias fragger Join Date: Jul 2003 Location: the Netherlands Posts: 863	See this and this thread on everwicked. It looks like this is a non-trivial change. And there are plenty directshow capping applications out there so you can always cap with those and process the capped video in vdub afterwards

26th April 2004, 14:29	#8 \| Link
WildCelt Registered User Join Date: Sep 2002 Location: Michigan Posts: 91	Thanks for the info. Yeah, I dumped vdub a while ago for raw capture. I get great results with VirtualVCR.