Capture a DVB-T Stream to a movie-file

Question

I have a form with a liveview of the tv-signal (from dvb-t stick). I've the sampleproject "DTViewer" from http://directshownet.sourceforge.net/about.html. Now I try to capture the stream to a movie-file by clicking a button, but how? I use C# and DirectShow.NET.

I tried to search in many sampleprojcets but these are made for videoinputs not a dvb-t stick with a BDA (Broadcast Driver Architecture) interface.

Help!

Answer 1

Don’t really know what exactly do you mean by a “movie-file”, but I can tell you how to capture the entire MUX (transport stream).

Create a graph with a Microsoft DVBT Network Provider, You_Name_It BDA DVBT Tuner, You_Name_It BDA Digital Capture and MPEG-2 Demultiplexer filters.
Once you connect them, enumerate all output pins on the MPEG-2 Demultiplexer and render them. Tune the frequency of your choice (put_TuneRequest).

At this point everything is ready to run the graph, but don’t run it!
Enumerate all filters in the graph. Disconnect all filters except Microsoft DVBT Network Provider, You_Name_It BDA DVBT Tuner and You_Name_It BDA Digital Capture.

Remove all these disconnected filters from the graph except the MPEG-2 Demultiplexer (it has to be in the graph although it is not connected). Add Sample Grabber filter and NULL Renderer filter. Connect Digital Capture filter to Sample Grabber and Sample Grabber to NULL Renderer. You can run the graph now. Through the callback in Sample Grabber filter you will receive the entire MUX. Of course, there is still some work to demux the data, but once you do that, you can capture all TV programs in one MUX at once. The easiest way is to capture it in a TS format because the TS is being broadcasted (188 bytes long packets).

Answer 2

It seems to me VLC has BDA support (BDA.c file reference), maybe you can snoop up something from their code?

Answer 3

There is no simple answer to your question. I have started one such project and have found out that there is very little I know about it, so here is little something from my research.

First, you'll have to understand that dvb-t tuner card or stick doesn't give video frames in the classical sense, but the decoding is done in the pc, on the cpu. External card will provide you with compressed data only, as it fetches it from the air.

Next - data that is delivered to you will be in MPEG2 or MPEG4 Transport Stream format. Which is suitable for streaming or broadcasting, not for saving to file. VLC is able to play TS written to the file, but to record a proper video file, you'll have to either transcode the file or repack it to Program Stream. Google it a little, you'll find the differences.

More - one frequency on the air consists of many channels, and that channel packing is called 'mux'. So - from the BDA tuner/capturer you'll get ALL data, and you'll have to demux it manually or let BDA demuxer do it for you.

Hope that's enough info to get you started, I can post you some interesting links when I get to the real keyboard.