This source-node receives digital-video-broadcasts from satellite via a DVB-compatible PCI-Card
(using siemens-dvb-driver v0.9.3). To access the DVB-hardware it uses a modified version of the dvbapi from
VDR (0.80)
It needs a channel.conf-file with information about received channels.
It outputs raw YUV2 pictures or a MPEG-PES-stream (packetized elementary stream) which also contains audio.

The following events are generated after a channel-switch:

  YUV:	- start_track(string channel_name)
  MPEG: - resync_mpeg_decoder
          This tells the mpeg-decoder to discard P- and B-frames until the next I-frame arrived,
	      which is necessary because they are temporal reffering to pictures that have been send before
	      the channel was tuned
        - sync_reset
	      This is necessary because streams from different channels might have different timestamps
	    - start_track(string channel_name)

Before the first YUV-picture a resolution_changed(int width, int height)-event is sent containing the 
resolution choosen by the controlling application on format setup.
Also different channels are using different resolutions, the resolution of the YUV-pictures does not 
change on channel-switch because scaling is done by the video-4-linux-api. If using MPEG-output a
resolution-change must be detected by the mpeg-decoder. 