Demodulator

From LinuxTVWiki
Revision as of 04:40, 11 January 2008 by CityK (Talk | contribs)

Jump to: navigation, search

A Demodulator (short Demod) recovers (demodulates) the original information from the received and downconverted RF signal -- a tuner acquires the RF signal and converts it to an intermediate frequency (IF) which is then passed onto the demodulator for processing. The type of demodulator IC used for this task of information recovery is specific and dependent upon the nature of the signal transmission scheme involved.

In the case of analog TV, the IF inputted into the demodulator contains the composite signal that was originally modulated onto the RF carrier. After recovery, the demodulator outputs a CVSB signal, which will then need to be digitized through sampling techniques performed by a A/V decoder.

In the case of digital TV transmission schemes, the IF inputted into the demodulator contains a MPEG-2 Transport Stream (TS) that was originally modulated onto the RF carrier. In the process of recovering that TS, digital demodulators will perform Forward Error Correction (Convolutional Viterbi- and Block-Reed-Solomon-Decoding). This whole process is sometimes referred to as RF-to-bits, for, unlike the case with analog IF demodulators, the recovered signal outputted from the digital demodulator is already a digital bit stream; specifically a TS. The TS will in turn be sent to a decoder in order to display (and, depending upon what format the underlying video content contained within the TS was encoded with, this could be a MPEG-2 or MPEG-4 decoder ... and either hardware or software based).

Demodulator Chipsets

Analogue IF Demodulators

A Sortable List of Analog IF Demodulators
Vendor Model Standards Linux Support Comments
Philips TDA9887 NTSC Yes -
Xceive XC3028 NTSC, PAL er, somewhat firmware galore
Xceive XC5000 NTSC, PAL er, somewhat firmware galore

... and so on ...

Digital Demodulators

A Sortable List of Digital Demodulators
Vendor Model Standard Linux Support Comments
ATI/AMD Nxt2000 ATSC  ? Supports 8-VSB, QAM; firmware required
ATI/AMD Nxt2002 ATSC yes Supports 8-VSB, QAM; firmware required
ATI/AMD Nxt2004 ATSC yes Supports 8-VSB, QAM; firmware required
ATI/AMD NXT6000 DVB-T yes Supports COFDM
ATI/AMD Theater 31x ATSC no Supports 8-VSB, QAM
Atmel AT76C651 DVB-C  ? supports QAM
Conexant CX24116 DVB-S2  ?
Conexant CX22700 DVB-T yes Supports COFDM
Conexant CX24110 DVB-S yes supports QPSK
DiBcom DIB3000M DVB-T yes supports COFDM
LG DT3302 ATSC yes Supports 8-VSB, QAM
LG DT3303 ATSC yes Supports 8-VSB, QAM
LSI Logic Corporation L64781 DVB-T yes Supports COFDM
LSI Logic Corporation L64782 DVB-T yes Supports COFDM
Microtune MT8872 DVB-T  ? COFDM
Philips TDA10021 DVB-C yes Supports QAM
Philips TDA10045 DVB-T yes Supports COFDM
Philips TDA10046 DVB-T yes Supports COFDM
Philips TDA8083 DVB-S yes supports QPSK
Samsung s5h1409 ATSC yes Supports 8-VSB, QAM. Also known as the Conexant CX..
Samsung s5h1411 ATSC yes Supports 8-VSB, QAM.
SPaSE SP8870 DVB-T  ? supports COFDM
SPaSE SP8872 DVB-T  ? COFDM
STMicroelectronics STV0297 DVB-C yes supports QAM
STMicroelectronics STV0299 DVB-S yes supports QPSK
STMicroelectronics STB0899 DVB-S2 yes supports 8PSK, QPSK, 16APSK
STMicroelectronics STV0900/3 DVB-S2  ? supports QPSK
VLSI Technology VES1893 DVB-S yes supports QPSK
VLSI Technology VES1993 DVB-S yes supports QPSK
VLSI Technology VES1820 DVB-C yes supports QAM
Zarlink Semiconductor MT312 DVB-S/DSS yes supports QPSK
Zarlink Semiconductor MT352 DVB-T yes supports COFDM
Zarlink Semiconductor ZL10312 DVB-S/DSS no supports QPSK
Zarlink Semiconductor ZL10313 DVB-S/DSS no supports QPSK

...and so on ...

Note: Info below needs to be added to table above

ATSC Demodulators

  • Oren or51211
  • Oren or51132
  • Zoran/Oren Cascade2 (CAS-220)

....

DVB-T Demodulators

...

DVB-S2 Demodulators




Also see