Peter Gutmanns Cost Analysis of Microsoft Vista only scratches the surface of the whole problem of content capture and handling. A key problematic piece in this whole puzzle is a technology called DirectShow. Microsoft contracted Geraint Davies several years ago to create a component based media streaming system. It is really well designed, it has its kinks, but works sufficiently reliable. However it aged and seems to be abandoned now. Microsoft also disguised its existence with shuffling it around various times with a recent move out of DirectX into the Platform SDK. The developer library apparently also doesn't work with Visual Studio 2005 unless you are a black belt C/C++ programmer patching your way through the headers.




It seems strange to hide a good piece of software from the user and the developer one would think. But if you know the inner workings of it you realize it is not random nor is DirectShow a forgotten gem which needs to be rediscovered.

With DirectShow you can extend the pipeline with filters as you like. Projects like ffdshow demonstrate how you can actually use an excellent open source codec easily within the otherwise proprietary DirectShow pipeline. Another major problem is that you are able to intercept running pipelines with a tool called GraphEdit. This allows you to hook into a running pipeline (taking granted it will be announced in the so called ROT - but you can force it actually) and add filters and tee in order to see whats going on there.

So why I bring this up - it allows you to actually get raw access your preciouuuusss (sorry I couldn't resist) "premium" content you most probably paid with your first born and your own soul. DirectShow can't handle DRM and therefore publisher aren't really keen on it and desparetely waiting for Vista.

A glimpse in the documentation for the successor Windows Media Foundation reveals that it will solve all of these problems for Microsoftyou and you will never be bothered with the choice of having another copy or able to otherwise reuse your content.

A second glimpse, more deeply makes you aware that Microsoft doesn't want you to know how it works and how you can create components for it. And they also provide you a nice explanation (my comments in bold):

• The pipeline in DirectShow tends to be static. Implementing dynamic graphs and major format changes is a complex task.Half Bogus: nice try, this only is true for the current state of DirectShow - if anybody would have spent a bit of time on it also could do dynamic graphs
• The threading model for DirectShow filters is complex and requires a thorough understanding to implement correctly.Bogus: kids don't play with DirectShow - only grown up educated people who are willing to read a documentation
• Filters cannot be used easily outside of a DirectShow graph, which ties them to the DirectShow pipeline. Utter bogus: Who expects a DirectShow component to be used outside of the filtergraph? Do you fly with your bicycle?
• DirectShow does not readily support protected content.The only and real issue

Slightly lower in the list we have a better overview (from here with comments):

Feature group	Feature	Media Foundation	DirectShow
Basic functionality	Audio and video rendering	Yes	Yes
	Event notification	Yes	Yes
	Device enumeration	No	Yes	Crippled (prevent abitrary capture components to be selected)
	Component enumeration	Yes	Yes
	Synchronization to reference clock	Yes	Yes
	Seeking	Yes	Yes
	Improved stress resilience	Yes	No	Improvement, however I rarely seen an unresponsive DirectShow pipeline
Content protection	Component validation	Yes	No	Crippled - preventing components like ffdshow within a Media Foundation graph
	Content protection policy negotiation	Yes	No	Crippled - content protection policies could be implemented in the filters
	Interoperability between content protection technologies	Yes	No	Crippled - expect to sign an NDA and several other documents before you will be able to hook into the content protection - basically this is only for the big boys
	Protection against kernel-mode and user-mode threats	Yes	No	Improvement: some weired DirectShow components could bring down a whole system
	Component revocation and renewal	Yes	No	Crippled - you can only add components that behave - Microsoft will decide for you
	Video output protection management	Yes	Yes
Media tasks	Audio capture	No	Yes	Crippled: You dare to capture audio? RIAA on your doorstep
	Video capture	No	Yes	Crippled: You dare to capture video? See audio and add the guys from Paramount and Co.
	Video editing	No	Yes	Crippled: Mash Up with your own funky software? Forget it! Windows Movie Maker Rulez!
	DVD playback and navigation	No	Yes	Crippled - Evil DVDs - that where the big boys loosing all their money
	MPEG-2 support	No	Yes	Crippled - Dead old tech isn't it. Bloody DVDs
	ASF support	No	Yes	Crippled - Fortunately!
	TV technologies	No	Yes	Crippled - Who needs TV anyway?
	Stream buffer engine	No	Yes	Crippled - streaming video probably later only with WMV
	Encoder API	No	Yes	Crippled - cross coding anybody?
Video renderer	Substream mixing using per-pixel or planar alpha blending	Yes	Yes
	Customizable video composition	No	Yes	Crippled - you dare to touch the preciouuus premium pixels?
	Support for custom presenters	Yes	Yes
	Windowless rendering	Yes	Yes
	Multimonitor support	Yes	Yes
	DXVA	Yes	Yes
	DirectDraw exclusive mode	Yes	Yes
	Backward compatibility with existing applications	Yes	Yes
	Accurate frame stepping	Yes	Yes
	Alpha blending of image data	Yes	Yes
	Glitch resilience	Yes	No	Improvement
	Enhanced video fidelity	Yes	No	Improvement (Precious!)
	Enhanced content protection robustness	Yes	No	Har har har!
	Standalone use	Yes	No	Riding bicycles through the air
	Standalone mixing component	Yes	No	dito
Transforms (MFT or DMO)	Synchronous data processing	Yes	Yes	Improvement
	Simple programming model	Yes	Yes
	Standalone use	Yes	Yes
	Multiple inputs and multiple outputs	Yes	Yes
	Dynamic number of streams	Yes	No	Improvement
	Access to sample-level metadata	Yes	No	Improvement
	In-place processing	Yes	Yes
	Dynamic format changes	Yes	No	Improvement
	Quality adjustment	Yes	No	Improvement (Precious on VGA aint no good)
	Rate change	Yes	No	Improvement

Thanks for your interesting article. I have done a small amount of directshow programming but would consider myself a beginner (haven't yet started building my own filters just link other filters up), is there anywhere (forum etc) you can recommend that I can learn more about directshow?

Specifically I am interested in forcing applications to register with the ROT so I can look at them within graphedit and reverse engineering filters so I can use interfaces without need of filter documentation which may not be available to me ;-)

Many thanks,

Seb