From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/DocBook/dvb/intro.xml | 191 ++++++++++++++++++++++++++++++++++++ 1 file changed, 191 insertions(+) create mode 100644 Documentation/DocBook/dvb/intro.xml (limited to 'Documentation/DocBook/dvb/intro.xml') diff --git a/Documentation/DocBook/dvb/intro.xml b/Documentation/DocBook/dvb/intro.xml new file mode 100644 index 00000000..0dc83f67 --- /dev/null +++ b/Documentation/DocBook/dvb/intro.xml @@ -0,0 +1,191 @@ +Introduction + +
+What you need to know + +The reader of this document is required to have some knowledge in +the area of digital video broadcasting (DVB) and should be familiar with +part I of the MPEG2 specification ISO/IEC 13818 (aka ITU-T H.222), i.e +you should know what a program/transport stream (PS/TS) is and what is +meant by a packetized elementary stream (PES) or an I-frame. + +Various DVB standards documents are available from + and/or +. + +It is also necessary to know how to access unix/linux devices and +how to use ioctl calls. This also includes the knowledge of C or C++. + +
+ +
+History + +The first API for DVB cards we used at Convergence in late 1999 +was an extension of the Video4Linux API which was primarily developed +for frame grabber cards. As such it was not really well suited to be +used for DVB cards and their new features like recording MPEG streams +and filtering several section and PES data streams at the same time. + + +In early 2000, we were approached by Nokia with a proposal for a +new standard Linux DVB API. As a commitment to the development of +terminals based on open standards, Nokia and Convergence made it +available to all Linux developers and published it on + in September 2000. +Convergence is the maintainer of the Linux DVB API. Together with the +LinuxTV community (i.e. you, the reader of this document), the Linux DVB +API will be constantly reviewed and improved. With the Linux driver for +the Siemens/Hauppauge DVB PCI card Convergence provides a first +implementation of the Linux DVB API. +
+ +
+Overview + +
+Components of a DVB card/STB + + + + + + + + +
+ +A DVB PCI card or DVB set-top-box (STB) usually consists of the +following main hardware components: + + + + +Frontend consisting of tuner and DVB demodulator + +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. + + + + +Conditional Access (CA) hardware like CI adapters and smartcard slots + + +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. + + + + Demultiplexer which filters the incoming DVB stream + +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. + + + + +MPEG2 audio and video decoder + +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. + + + + + + shows a crude schematic of the control and data flow +between those components. + +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. + +
+ +
+Linux DVB Devices + +The Linux DVB API lets you control these hardware components +through currently six Unix-style character devices for video, audio, +frontend, demux, CA and IP-over-DVB networking. The video and audio +devices control the MPEG2 decoder hardware, the frontend device the +tuner and the DVB demodulator. The demux device gives you control over +the PES and section filters of the hardware. If the hardware does not +support filtering these filters can be implemented in software. Finally, +the CA device controls all the conditional access capabilities of the +hardware. It can depend on the individual security requirements of the +platform, if and how many of the CA functions are made available to the +application through this device. + +All devices can be found in the /dev +tree under /dev/dvb. The individual devices +are called: + + + + +/dev/dvb/adapterN/audioM, + + +/dev/dvb/adapterN/videoM, + + +/dev/dvb/adapterN/frontendM, + + + +/dev/dvb/adapterN/netM, + + + +/dev/dvb/adapterN/demuxM, + + + +/dev/dvb/adapterN/caM, + +where N enumerates the DVB PCI cards in a system starting +from 0, and M enumerates the devices of each type within each +adapter, starting from 0, too. We will omit the “/dev/dvb/adapterN/” in the further dicussion +of these devices. The naming scheme for the devices is the same wheter +devfs is used or not. + +More details about the data structures and function calls of all +the devices are described in the following chapters. + +
+ +
+API include files + +For each of the DVB devices a corresponding include file exists. +The DVB API include files should be included in application sources with +a partial path like: + + + + #include <linux/dvb/frontend.h> + + +To enable applications to support different API version, an +additional include file linux/dvb/version.h exists, which defines the +constant DVB_API_VERSION. This document +describes DVB_API_VERSION 3. + + +
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