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+HOWTO: Get An Avermedia DVB-T working under Linux
+ ______________________________________________
+ Table of Contents
+ Assumptions and Introduction
+ The Avermedia DVB-T
+ Getting the card going
+ Receiving DVB-T in Australia
+ Known Limitations
+ Further Update
+Assumptions and Introduction
+ It is assumed that the reader understands the basic structure
+ of the Linux Kernel DVB drivers and the general principles of
+ Digital TV.
+ One significant difference between Digital TV and Analogue TV
+ that the unwary (like myself) should consider is that,
+ although the component structure of budget DVB-T cards are
+ substantially similar to Analogue TV cards, they function in
+ substantially different ways.
+ The purpose of an Analogue TV is to receive and display an
+ Analogue Television signal. An Analogue TV signal (otherwise
+ known as composite video) is an analogue encoding of a
+ sequence of image frames (25 per second) rasterised using an
+ interlacing technique. Interlacing takes two fields to
+ represent one frame. Computers today are at their best when
+ dealing with digital signals, not analogue signals and a
+ composite video signal is about as far removed from a digital
+ data stream as you can get. Therefore, an Analogue TV card for
+ a PC has the following purpose:
+ * Tune the receiver to receive a broadcast signal
+ * demodulate the broadcast signal
+ * demultiplex the analogue video signal and analogue audio
+ signal (note some countries employ a digital audio signal
+ embedded within the modulated composite analogue signal -
+ * digitize the analogue video signal and make the resulting
+ datastream available to the data bus.
+ The digital datastream from an Analogue TV card is generated
+ by circuitry on the card and is often presented uncompressed.
+ For a PAL TV signal encoded at a resolution of 768x576 24-bit
+ color pixels over 25 frames per second - a fair amount of data
+ is generated and must be proceesed by the PC before it can be
+ displayed on the video monitor screen. Some Analogue TV cards
+ for PC's have onboard MPEG2 encoders which permit the raw
+ digital data stream to be presented to the PC in an encoded
+ and compressed form - similar to the form that is used in
+ Digital TV.
+ The purpose of a simple budget digital TV card (DVB-T,C or S)
+ is to simply:
+ * Tune the received to receive a broadcast signal.
+ * Extract the encoded digital datastream from the broadcast
+ signal.
+ * Make the encoded digital datastream (MPEG2) available to
+ the data bus.
+ The significant difference between the two is that the tuner
+ on the analogue TV card spits out an Analogue signal, whereas
+ the tuner on the digital TV card spits out a compressed
+ encoded digital datastream. As the signal is already
+ digitised, it is trivial to pass this datastream to the PC
+ databus with minimal additional processing and then extract
+ the digital video and audio datastreams passing them to the
+ appropriate software or hardware for decoding and viewing.
+ _________________________________________________________
+The Avermedia DVB-T
+ The Avermedia DVB-T is a budget PCI DVB card. It has 3 inputs:
+ * RF Tuner Input
+ * Composite Video Input (RCA Jack)
+ * SVIDEO Input (Mini-DIN)
+ The RF Tuner Input is the input to the tuner module of the
+ card. The Tuner is otherwise known as the "Frontend" . The
+ Frontend of the Avermedia DVB-T is a Microtune 7202D. A timely
+ post to the linux-dvb mailing list ascertained that the
+ Microtune 7202D is supported by the sp887x driver which is
+ found in the dvb-hw CVS module.
+ The DVB-T card is based around the BT878 chip which is a very
+ common multimedia bridge and often found on Analogue TV cards.
+ There is no on-board MPEG2 decoder, which means that all MPEG2
+ decoding must be done in software, or if you have one, on an
+ MPEG2 hardware decoding card or chipset.
+ _________________________________________________________
+Getting the card going
+ In order to fire up the card, it is necessary to load a number
+ of modules from the DVB driver set. Prior to this it will have
+ been necessary to download these drivers from the linuxtv CVS
+ server and compile them successfully.
+ Depending on the card's feature set, the Device Driver API for
+ DVB under Linux will expose some of the following device files
+ in the /dev tree:
+ * /dev/dvb/adapter0/audio0
+ * /dev/dvb/adapter0/ca0
+ * /dev/dvb/adapter0/demux0
+ * /dev/dvb/adapter0/dvr0
+ * /dev/dvb/adapter0/frontend0
+ * /dev/dvb/adapter0/net0
+ * /dev/dvb/adapter0/osd0
+ * /dev/dvb/adapter0/video0
+ The primary device nodes that we are interested in (at this
+ stage) for the Avermedia DVB-T are:
+ * /dev/dvb/adapter0/dvr0
+ * /dev/dvb/adapter0/frontend0
+ The dvr0 device node is used to read the MPEG2 Data Stream and
+ the frontend0 node is used to tune the frontend tuner module.
+ At this stage, it has not been able to ascertain the
+ functionality of the remaining device nodes in respect of the
+ Avermedia DVBT. However, full functionality in respect of
+ tuning, receiving and supplying the MPEG2 data stream is
+ possible with the currently available versions of the driver.
+ It may be possible that additional functionality is available
+ from the card (i.e. viewing the additional analogue inputs
+ that the card presents), but this has not been tested yet. If
+ I get around to this, I'll update the document with whatever I
+ find.
+ To power up the card, load the following modules in the
+ following order:
+ * insmod dvb-core.o
+ * modprobe bttv.o
+ * insmod bt878.o
+ * insmod dvb-bt8xx.o
+ * insmod sp887x.o
+ Insertion of these modules into the running kernel will
+ activate the appropriate DVB device nodes. It is then possible
+ to start accessing the card with utilities such as scan, tzap,
+ dvbstream etc.
+ The frontend module sp887x.o, requires an external firmware.
+ Please use the command "get_dvb_firmware sp887x" to download
+ it. Then copy it to /usr/lib/hotplug/firmware.
+Receiving DVB-T in Australia
+ I have no experience of DVB-T in other countries other than
+ Australia, so I will attempt to explain how it works here in
+ Melbourne and how this affects the configuration of the DVB-T
+ card.
+ The Digital Broadcasting Australia website has a Reception
+ locatortool which provides information on transponder channels
+ and frequencies. My local transmitter happens to be Mount
+ Dandenong.
+ The frequencies broadcast by Mount Dandenong are:
+ Table 1. Transponder Frequencies Mount Dandenong, Vic, Aus.
+ Broadcaster Channel Frequency
+ ABC VHF 12 226.5 MHz
+ TEN VHF 11 219.5 MHz
+ NINE VHF 8 191.625 MHz
+ SEVEN VHF 6 177.5 MHz
+ SBS UHF 29 536.5 MHz
+ The Scan utility has a set of compiled-in defaults for various
+ countries and regions, but if they do not suit, or if you have
+ a pre-compiled scan binary, you can specify a data file on the
+ command line which contains the transponder frequencies. Here
+ is a sample file for the above channel transponders:
+# Data file for DVB scan program
+# C Frequency SymbolRate FEC QAM
+# S Frequency Polarisation SymbolRate FEC
+# T Frequency Bandwidth FEC FEC2 QAM Mode Guard Hier
+T 226500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
+T 191625000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
+T 219500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
+T 177500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
+T 536500000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
+ The defaults for the transponder frequency and other
+ modulation parameters were obtained from www.dba.org.au.
+ When Scan runs, it will output channels.conf information for
+ any channel's transponders which the card's frontend can lock
+ onto. (i.e. any whose signal is strong enough at your
+ antenna).
+ Here's my channels.conf file for anyone who's interested:
+ABC TV Melbourne:226500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_
+TEN Digital 1:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q
+TEN Digital 2:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q
+TEN Digital 3:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q
+TEN Digital 4:219500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:Q
+Nine Digital:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QA
+Nine Digital HD:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2
+Nine Guide:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_
+7 Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_6
+7 Digital 1:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM
+7 Digital 2:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM
+7 Digital 3:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM
+7 HD Digital:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QA
+7 Program Guide:177500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3
+ _________________________________________________________
+Known Limitations
+ At present I can say with confidence that the frontend tunes
+ via /dev/dvb/adapter{x}/frontend0 and supplies an MPEG2 stream
+ via /dev/dvb/adapter{x}/dvr0. I have not tested the
+ functionality of any other part of the card yet. I will do so
+ over time and update this document.
+ There are some limitations in the i2c layer due to a returned
+ error message inconsistency. Although this generates errors in
+ dmesg and the system logs, it does not appear to affect the
+ ability of the frontend to function correctly.
+ _________________________________________________________
+Further Update
+ dvbstream and VideoLAN Client on windows works a treat with
+ DVB, in fact this is currently serving as my main way of
+ viewing DVB-T at the moment. Additionally, VLC is happily
+ decoding HDTV signals, although the PC is dropping the odd
+ frame here and there - I assume due to processing capability -
+ as all the decoding is being done under windows in software.
+ Many thanks to Nigel Pearson for the updates to this document
+ since the recent revision of the driver.
+ January 29th 2004