1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Overview</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API"><link rel="up" href="dvb_introdution.html" title="Chapter 8. Introduction"><link rel="prev" href="history.html" title="History"><link rel="next" href="dvb_devices.html" title="Linux DVB Devices"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Overview</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="history.html">Prev</a> </td><th width="60%" align="center">Chapter 8. Introduction</th><td width="20%" align="right"> <a accesskey="n" href="dvb_devices.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="overview"></a>Overview</h2></div></div></div><div class="figure"><a name="stb_components"></a><p class="title"><b>Figure 8.1. Components of a DVB card/STB</b></p><div class="figure-contents"><div class="mediaobject"><img src="dvbstb.png" alt="Components of a DVB card/STB"></div></div></div><br class="figure-break"><p>A DVB PCI card or DVB set-top-box (STB) usually consists of the 2following main hardware components: </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Frontend consisting of tuner and DVB demodulator</p><p>Here the raw signal reaches the DVB hardware from a satellite dish 3or antenna or directly from cable. The frontend down-converts and 4demodulates this signal into an MPEG transport stream (TS). In case of a 5satellite frontend, this includes a facility for satellite equipment 6control (SEC), which allows control of LNB polarization, multi feed 7switches or dish rotors.</p></li><li class="listitem"><p>Conditional Access (CA) hardware like CI adapters and smartcard slots 8</p><p>The complete TS is passed through the CA hardware. Programs to 9which the user has access (controlled by the smart card) are decoded in 10real time and re-inserted into the TS.</p></li><li class="listitem"><p>Demultiplexer which filters the incoming DVB stream</p><p>The demultiplexer splits the TS into its components like audio and 11video streams. Besides usually several of such audio and video streams 12it also contains data streams with information about the programs 13offered in this or other streams of the same provider.</p></li><li class="listitem"><p>MPEG2 audio and video decoder</p><p>The main targets of the demultiplexer are the MPEG2 audio and 14video decoders. After decoding they pass on the uncompressed audio and 15video to the computer screen or (through a PAL/NTSC encoder) to a TV 16set.</p></li></ul></div><p><a class="xref" href="overview.html#stb_components" title="Figure 8.1. Components of a DVB card/STB">Figure 8.1, “Components of a DVB card/STB”</a> shows a crude schematic of the control and data flow 17between those components.</p><p>On a DVB PCI card not all of these have to be present since some 18functionality can be provided by the main CPU of the PC (e.g. MPEG 19picture and sound decoding) or is not needed (e.g. for data-only uses 20like “internet over satellite”). Also not every card or STB 21provides conditional access hardware.</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="history.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="dvb_introdution.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="dvb_devices.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">History </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Linux DVB Devices</td></tr></table></div></body></html> 22
