News Marquee over analog TV stream - C#

Question

I want to put a news marquee over an analog TV stream using c#, I can stream analog TV using DirectShow but I can't figure out how to mix it with rotating text, should I create a filter? or I have to use another technology than DirectShow?

Answer 1

DirectShow is the simplest way of doing this but it does have a bit of a learning curve, particularly coming from C#. The Wikipedia page gives you a basic overview of DirectShow.

DirectShow tools are available in the latest Windows SDK. Using C++ for DirectShow programming is more straightforward but you can use DirectShow fairly easily via COM interop or DirectShow.net (which I haven't tried yet). If using COM interop the following article is helpful:

http://blogs.msdn.com/b/ericgu/archive/2004/09/20/232027.aspx

You may be able to use the VMR overlay filter if the animation performance is smooth enough. See the following articles

http://www.codeproject.com/KB/audio-video/VideoPicture.aspx
http://www.codeproject.com/KB/audio-video/Ticker.aspx
http://msdn.microsoft.com/en-us/library/dd407344(v=vs.85).aspx

Alternatively you will need to write your own filter that renders the text on each frame adjusting its position in synch with the time stamps of the video frames. If you only need to do this inside your own application then the following approach might be easiest

http://www.sichbo.ca/Free_Code/100_C_Sharp_directshow_filters

Microsoft officially recommend that DirectShow filters should be created in C++ for performance reasons but overlaying scrolling text should be OK in C# as the bottleneck will be the APIs used to overlay the text if you program carefully.

Answer 2

Actually you don't have to write a filter to draw some text over your video. Just make a graph where uncompressed video goes through sample grabber (one of standard DirectShow filters), set up a callback for the sample grabber and you'll be able to modify the video data in your callback. Doing it in C# is very easy using DirectShow.NET but not optimal due to marshalling. You can first build such a graph in GraphEditPlus, then it will show you source code in C# or C++ of how to build this graph and use sample grabber.