<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Overview</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="ch08.html" title="Chapter 8. Introduction" /><link rel="prev" href="ch08s02.html" title="History" /><link rel="next" href="ch08s04.html" title="Linux DVB Devices" /></head><body><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="ch08s02.html">Prev</a> </td><th width="60%" align="center">Chapter 8. Introduction</th><td width="20%" align="right"> <a accesskey="n" href="ch08s04.html">Next</a></td></tr></table><hr /></div><div class="section" title="Overview"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="overview"></a>Overview</h2></div></div></div><div class="figure"><a id="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 following main hardware components: </p><div class="itemizedlist"><ul class="itemizedlist" 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 or antenna or directly from cable. The frontend down-converts and demodulates this signal into an MPEG transport stream (TS). In case of a satellite frontend, this includes a facility for satellite equipment control (SEC), which allows control of LNB polarization, multi feed switches or dish rotors.</p></li><li class="listitem"><p>Conditional Access (CA) hardware like CI adapters and smartcard slots </p><p>The complete TS is passed through the CA hardware. Programs to which the user has access (controlled by the smart card) are decoded in real 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 video streams. Besides usually several of such audio and video streams it also contains data streams with information about the programs offered 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 video decoders. After decoding they pass on the uncompressed audio and video to the computer screen or (through a PAL/NTSC encoder) to a TV set.</p></li></ul></div><p><a class="xref" href="ch08s03.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 between those components.</p><p>On a DVB PCI card not all of these have to be present since some functionality can be provided by the main CPU of the PC (e.g. MPEG picture and sound decoding) or is not needed (e.g. for data-only uses like “internet over satellite”). Also not every card or STB provides 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="ch08s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch08.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch08s04.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>
