[mythtv] Semi-OT: Which HDTV card to buy for Myth?
rtjacob at earthlink.net
Sun Jan 30 16:00:24 EST 2005
Quoting Cory Papenfuss <papenfuss at juneau.me.vt.edu>:
> The pcHDTV card has the following:
> - Standard i2c-controlled RF frontend for tuning and downconversion to
> - CX88-based PCI/DMA inteface between the Oren chip and the PCI bus
> - CX88-based analog capture (as a side-benefit from using it as an
> - Oren baseband demod chip that can do VSB and potentially QAM. BUT, this
> chip is configured via a closed chunk of binary code. Thus the dependence
> on Oren and why the pcHDTV-2000 doesn't and probably won't support
> unencrypted QAM.
That sounds right, but I would go with Daniels word if he says its different..
> The Air2PC card has the following:
> - Standard i2c-controlled RF frontend like pcHDTV card
> - nxt2002 baseband digital demodulator (comparable to the Oren chip). It
> can do VSB and QAM (unencrypted), but is also programmed via binary-only
> firmware. The nxt2002 "driver" basically just loads the firmware.
> - FlexCop ASIC to do both MPEG-TS PID filtering and PCI/DMA interfacing.
One correction.. The Oren is a 2nd gen demodulator, where as the nxt2002 is a
4th gen demodulator, so there are some slight differences there..
> Is that about right? Honestly, I'm a bit concerned about the
> longevity and support of drivers dependent on firmware snarfed from other
> drivers. Once the broadcast flag is permanent, who's to say that the
> firmware won't get "fixed" to enforce it. Call me paranoid, I guess... :)
Well the firmware for the demodulators will never be capable of actually doing
anything with the data its demodulating. The FlexCop Firmware used by the
Air2PC is loaded from an eeprom on the board, and is the same as the SkyStar2
firmware used for DVB-S. To "fix" the firmware for the flexcop you are going
to have to modify the eeprom yourself.
You seem to be worrying about a the broadcast flag way too much. It is simply a
descriptor in the EIT. The pcHDTV and the Air2PC do not have the hardware on
board to anaylze the stream enough to parse the MGT, VCT, STT and then the EIT
to determine if its to either encrypt the data, or downconvert the HD mpeg to
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