Quoting Cory Papenfuss <[EMAIL PROTECTED]>:From what I've read on it today, it has a subset MPEG decoder. It won't play video, but it will interpret enough of the MPEG-TS stream to filter out specific PIDs. In other words, if one is receiving a station that has a simultaneous SD and HD within the same "channel," then the card itself can choose only one or the other.
The Flexcop handles the MpegTransport Stream. It is not a "subset MPEG decoder". The flexcop can filter up to 38 PIDs at the same time. This means you can record more than 1 station at a time. If you exceed 38 pids then you are in trouble. Most channels will be 2 PIDs (Audio + Video). So you do the math.
OK... poor choice of wording, perhaps. I would consider the PID filtering a sort of MPEG processing... maybe not decoding, but an MPEG stream processor. Am I correct in saying that the FlexCop in the Air2PC-ATSC can selectively filter out PIDs (in a multiple station/channel setup), whereas the pcHDTV card cannot? The latter simply dumps the raw MPEG-TS stream without any filtering?
Feel free to correct any errors here, but I'm trying to get a handle on the differences between the two cards. In particular, the "open-ness" of the hardware/driver. From my understanding:
The pcHDTV card has the following:
- Standard i2c-controlled RF frontend for tuning and downconversion to baseband.
- 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 interface)
- 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.
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.
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... :)
-Cory
All digital TV cards do not do anything with Mpeg. They are simply transporting a datastream. It could be anything they send, it just happens to be Mpeg we use it for.
Taylor
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
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