There are two ways:
Hardware video decoder
The principle of the VDR software is avoiding to deal with MPEG data on software side as much as possible. For viewing of the video stream provided by the DVB card, a hardware video decoder can be used. There are few possibilities for decoding video on hardware:
Full-featured DVB card
Full featured DVB card has the tuner and also hardware video decoder with TV-Out
Dxr3 or Hollywood-Plus MPEG decoder card
MPEG decoder card, originally used for DVD viewing on slow computers. The current status (April 2013) is that it cannot be used on stable VDR-2.0.0 because VDR requires DVB driver api 5.3 and the API is available in recent kernel versions which are not supported by the dxr3 driver anymore. The dxr3 driver has the em8300 decoder chip.
The previous stable VDR-1.6.0 can still work with dxr3 card and Linux kernels up to 2.6.37.
WinTV PVR350 is an old analogue TV card with onboard hardware MPEG2 decoder.
VDPAU capable video card
When using VDPAU capable video card the video is decoded "in software" by xineliboutput or similar plugin. It is then up to the plugin to use capabilities of the underlying hardware to decode the video as efficiently as possible in hardware. VDPAU api is meant for offloading video decoding to hardware. Many video card manufacturers are currently (2013) supporting it such as ATI/AMD, Intel and NVidia.
The main advantage of using the VDPAU api is that VDR can be run under Xorg and other software for Xorg can be used directly without modifications. The video out will then be a normal Xorg session with hardware for VDR.
Software MPEG decoder
Most input cards sold nowadays are so-called budget cards, i.e. they don't have hardware video decoders. The decoding is done by the CPU and the output is usually given to the normal graphic card. There are a number of VDR software decoder plugins available:
- Softdevice-plugin Provides excellent output on VGA hardware using X11 or DirectFB. Can also do hardware MPEG2 acceleration on motherboards provided with CLE266 chipset. Can also do field perfect interlaced output using Matrox G450/550 cards under DirectFB.
- Xine-plugin (requires xine, gxine or some other xine-lib front-end). Xine can also use the hardware MPEG2 acceleration feature of the EPIA M motherboards with CLE266 chipset. Software playback on EPIA.