Good HOWTO Mark. Just a few corrections on the less important details. On Thu, Jan 29, 2004 at 09:54:41PM +1100, Mark Edwards wrote: > > HOWTO: Get An Avermedia DVB-T working under Linux > ______________________________________________ > [...] > 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
Yes, the broadcast signal is AM video with an FM audio subcarrier. The tuner shifts this to a fixed intermediate frequency and the demodulator produces baseband video & audio. > * demultiplex the analogue video signal and analogue audio > signal (note some countries employ a digital audio signal > embedded within the modulated composite analogue signal - > NICAM.) Demultiplex is not quite the right word IMHO. Demultiplex implies that the audio and video signals are mixed in time; they're really mixed in frequency and both present all the time. The audio is on a subcarrier at a fixed offset from the video carrier. The audio and video would be demodulated individually (one is AM and the other FM). > 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. The tuner shifts the frequency to a known RF just like the analogue card, where you have an MPEG2 bitstream modulated through COFDM. Then you use a demodulator to recover the bits from the analog COFDM signal. > 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 SBS in Melbourne moved to 536.625 MHz a few weeks ago. > Nine Digital:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QA > M_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:513:660:10 > 72 These guys seem to have changed their video and audio pids at separate times in the last 24 hours. Fun! Now 519:720. > Nine Guide:191625000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_ > 64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:670:1074 514 changed too but I can't remember what to. Cheers Hamish -- Hamish Moffatt VK3SB <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> -- Info: To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe linux-dvb" as subject.
