Originally Posted by HDTimeShifter
with only one cable feed ... and one antenna...I can't tune 2 simultaneous ATSC stations or 2 simultaneous QAM stations (i.e., record one ATSC channel while watching another ATSC channel). This is somewhat more primitive than with analog, where I've been used to being able to watch one channel with the TV tuner ... while recording another channel on my VCR with it's tuner.
Its not more primitive. You just don't have all the pieces to the puzzle yet
I think that some of the descriptions above (and, specifically, their unintentional misuse of the word "tuners
") have mislead you to arrive at the wrong conclusion. I will try to fill in the gaps:
The HDHR has two receivers. The other devices discussed above are comprised by a single receiver.
There is a single
tuner in those receivers. That tuner can only lock onto one frequency at a time. It will then route the frequency that it has acquired to either (a) the analog demodulator or (b) the digital demodulator. The receiver, thus, can only be operating in a single mode; analog or digital, but not both simultaneously.
That digital demodulator will handle the demodulation of an OTA signal (8VSB) or a digital cable signal (64/256-QAM; and usually being 256-QAM). But it will NOT operate in both modes at the same time.
You can accomplish what you described above with analog tuners precisely because there are two separate tuners involved (one in your TV an one in the VCR, and an internal splitter that is routing the signal to each of these devices)
Likewise, you can accomplish this same level of functionality with digital equipment, whether you're talking set top boxes or computer cards, if you set up the same environment (i.e. have two receivers present).
As you can see, the devil is in the details.
I guess I'll have to settle for 2 tuners, with one hooked up to my cable input for QAM/NTSC (analog cable) and the other to my antenna for ATSC.
You can accomplish this with some of the supported devices (like the KWorld 11[0/5] cards, ATI HDTV Wonder, ..)
I had previously thought I should buy ATSC/QAM/NTSC tuners to be able to view or record from any of the 3 sources.
Well, you can, albeit, just not at the same time, given the physical and operational limitations described above.
Since all but the HDHomeRun tuners can only work with 1 source
As outlined above, this is precisely because all those other devices are comprised of a single receiver whereas the HDHR has two.
The Hauppauge HVR-1800 gained some support just recently. Like the HDHR, it also has two receivers (and in the case of the hvr-1800, one is strictly an analog receiver and the other a digital receiver). Currently, only support for digital reception is provided. Support for analog * (tv and a/v input) should follow hopefully ~months or so time.
* In this case, the analog receiver section is supported, but it is the analog functionality of the decoder (cx23887) that needs to be implemented. Once that support is added, you should be able to utilize both an analog and digital source simultaneously. The same caveat about the digital source limitation applies (8VSB or QAM; but not both at the same time). Also note that the hvr-1800 has a mpeg2 encoder (cx23417), but I don't know how far along support for that is (its essentially, AFAIK, a stripped down version of the earlier (and supported) cx23416 that appears in a number of analog devices featuring mpeg2 hardware encoding; think pvr-150, 500, 250....). In any regard, it should be possible to run the analog portion of the device entirely in "software mode" (i.e. circumvent the use of the cx23417) once analog support is added to the new cx23885/7 drivers. Support for the hardware encoding provided by the cx23417 would be the icing on the cake.
I may also be able to save money buy buying one ATSC-only tuner and one QAM-only tuner instead of 2 ATSC/QAM/NTSC tuners.
For the North American product space, there is no such thing as a QAM-only capable receiver device. The demodulators used for digital reception in products intended for N.A. will support both 8VSB and QAM.
On the flipside, you will, however, find devices that, despite containing a demodulator that supports both 8VSB & QAM, are capable of only providing OTA/8VSB support. This is because of either:
- drivers don't support QAM ... this is particularly true of use on a Windows OS platform, but much less so on Linux platforms (if QAM support can be figured out, then it will be added)
- a firmware is required, but one with QAM support is currently not available ... (ex. under Linux, the old pchdtv hd-2000)
- a hardware limitation ... example, devices using a xceive 3028 tuner ... the 3028 is incapable of acquiring a carrier frequency that uses 256-QAM for the underlying stream.
(don't think a splitter will even work since it must attenuate the signal too much... ended up scanning less channels than without a splitter
not all splitters are created equal..some are crap and can introduce loads of signal attenuation, while others much less so.
analog cable, which I think is NTSC
yes, in North America, analog tv (whether it is being served OTA or over cable) is conforming to NTSC
QAM (digital cable)
Just as an FYI, QAM is NOT equal to digital cable. It has, however, become colloquially known as digital cable.
ATSC governs digital OTA. ATSC uses 8VSB modulation.
Digital cable in N.A., on the other hand, doesn't have a convenient acronym (like "ATSC"), rather, is much more complicatedly described by ITU-T J.83, Annex B / ANSI/SCTE 07 (formerly SCTE DVS-031) / OpenCable. By defacto, the modulation scheme of choice for digital cable is QAM. But other modulation schemes have, can, and are used in digital cable.
In any regard, the general public and vendors alike in N.A. have picked up on the "QAM" association and have mis-equated it to be the standard for digital cable. The point that that is a misnomer is only driven home further by stepping outside N.A. to a region that adheres to DVB-C.