ATSC/QAM/NTSC Tuner Cards - AVS Forum
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post #1 of 22 Old 09-22-2007, 01:24 PM - Thread Starter
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Do all the ATSC/QAM/NTSC tuner cards have dual inputs for cable and antenna and Myth or the card automatically handle switching between inputs?

I wasn't aware that ATSC and QAM use the same frequencies and just bought a Samsung DTB-H260F to verify that I can receive my local OTA ok, but it has only 1 coax cable/antenna input, and when I tried hooking up a combiner for dual inputs, got less channels than either OTA or cable hooked up separately and found out that ATSC and QAM use the same frequencies so would have to use a switch. A manual A/B switch would certainly not be doable for PVR and a PITA for viewing; hopefully my Myth build won't require a computer switch with coax inputs and outputs.
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post #2 of 22 Old 09-22-2007, 02:36 PM
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My pcHDTV-5500s have one coax input that can be either ATSC/NTSC (antenna) or QAM (cable), I suspect other cards are the same. The only cards with two coax inputs are the dual-tuner ones. If you want to record antenna *and* cable at the same time (or without some manual switching/reconfiguring) you'll need multiple tuners.
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post #3 of 22 Old 09-22-2007, 04:46 PM
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My kworld dvico fusion 5 lite has one input that can do ATSC or analog and digital (QAM) cable. So I can record the basic cable stations or QAM stations without reconfiguring anything - just not at the same time of course because it isn't a dual tuner. My kworld ATSC 110s are in a similar boat, but they do use two different coax inputs. One for ATSC the other for QAM/analog cable, but you can't use both at the same time. The inputs on this one mysteriously have switched before (although not for me in quite a while). Some can use one input for ATSC/NTSC (cable and over the air) and the other input for QAM. http://www.mythtv.org/wiki/index.php/Kworld_ATSC_110.

Regardless, as posted earlier, you'll need dual tuners (HDhomerun might be good) if you want to do ATSC and QAM. Even if a single card can do both, I don't know how you would go about setting that up in myth.
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post #4 of 22 Old 09-22-2007, 06:01 PM
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You also mentioned NTSC. This would require a card with a NTSC (analog) tuner.

Some cards have both an analog and a digital tuner. But just like with the ATSC/QAM situation, you can only use one of the tuners at a time.

Unlike the ATSC/QAM situation, MythTV can be configured to use both of the tuners. I have not been able to get this to work to my satisfaction. Since the analog picture is crappy, at best, and the looming discontinuation of the analog broadcast, I have no reason to spend a lot of effort on it.
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post #5 of 22 Old 09-23-2007, 06:03 AM - Thread Starter
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I'm glad I found this out before I finalize the hardware for my Myth box. 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. I had previously thought I should buy ATSC/QAM/NTSC tuners to be able to view or record from any of the 3 sources. Since all but the HDHomeRun tuners can only work with 1 source without automatic switching, 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. Also with only one cable feed (don't think a splitter will even work since it must attenuate the signal too much as I've tried it with a Samsung DTB-H260F STB which ended up scanning less channels than without a splitter) and one antenna (coax splitter resulted in same problem as with cable - loss of channels), 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 (ex., Survivor) while recording another channel on my VCR with it's tuner (ex., Friends/Seinfield or whatever used to compete against Survivor back in the night).

The only reason for me wanting a tuner card with NTSC is for analog cable, which I think is NTSC. There are still some channels that aren't on QAM (digital cable) yet like SpeedTV. I have no need for OTA NTSC as all the locals are on ATSC (except one, which I can get via QAM).
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post #6 of 22 Old 09-23-2007, 11:09 AM
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Quote:
Originally Posted by HDTimeShifter View Post

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.

Quote:
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, ..)
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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.
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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.

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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.

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(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.

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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

Quote:
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.
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post #7 of 22 Old 09-24-2007, 03:15 AM - Thread Starter
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Ok, I've verified that I don't need NTSC since there are no analog cable channels that I care about that aren't on digital cable (I found the SpeedTV QAM channel). So that simplifies my setup a bit.

I want my Myth box to be able to handle each of the following situations:
1) Record 2 different QAM channels simultaneously, or
2) Record 2 different ATSC channels simultaneously, or
3) Record 1 QAM channel and 1 ATSC channel simultaneously, or
4) Record 1 QAM channel while I watch another QAM channel, or
5) Record 1 ATSC channel while I watch another ATSC channel, or
6) Record 1 QAM channel while I watch 1 ATSC channel, or
7) Record 1 ATSC channel while I watch 1 QAM channel.
8) Flip between viewing live ATSC or QAM channel and playing back a recorded program.

9) In addition, I would like to be able to do both 4, 5, 6, or 7 and flip between watching a live program and playing back a recorded program.

Comcast's HD-PVR is able to all of the above with just QAM.

Number 9 is an option I can live without.

I assume that having 2 single tuner cards with cable connected to one and antenna connected to the other will handle any of the above options where I need to tune 1 ATSC and 1 QAM channel, but not 2 ATSC channels or 2 QAM channels simultaneously. I assume an HDHR card has 2 coax inputs so I can effectively buy only 1 card instead of 2 single tuner cards, and it will handle simultaneous tuning of 1 ATSC channel and 1 QAM channel? Am I correct in thinking that I will need a decent splitter and 2 HDHR cards to be able to do all of the options above? I currently have a Radio Shack VHF/UHF/FM splitter, but it is crap as I loose channels (signal strength) with either antenna or cable hooked up to it. I don't understand how something as simple as 3 coax connecters can be crap. I guess I could have also use a splitter and hook up 2 cable coax leads to 2 single tuner cards, but then would loose capability doing the 1 ATSC/ 1 QAM options. So now I'm looking at buying 2 HDHR tuner cards. Also while there is an HDHR USB card, I assume there is also an HDHR PCI card? Is the USB interfance fast enough for HD video that I wouldn't need to use an HDHR PCI card? Most microATX boards limit me to only 2 or 3 regular PCI slots, so each USB card would free up a slot. Most motherboards these days seem to come with endless number of USB connectors. Otherwise I'm looking at a PCI sound card and 2 PCI tuner cards.
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post #8 of 22 Old 09-24-2007, 08:34 AM
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The HDHR (there's only the one by that name) is not a "card", it is a network attached device. This device has two independent digital (ATSC/QAM) tuners, each with a single coax input, along with an IR port for remote control and the network connection. So it doesn't take any slots or USB ports away from your computer.

To achieve your goal of dual ATSC or dual QAM recordings, perhaps you should buy two HDHRs so you won't have to remember to flip an A/B switch depending on recording schedules - actually this would enable dual ATSC *and* dual QAM recordings simultaneously. Each stream to the PC is up to 20Mbit/s, so four should fit on one 100Mbit/s connection; or you could run each HDHR into its own network card on the PC if you feel like it. Gigabit switching and gigabit on the PC should also be more than sufficient.
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post #9 of 22 Old 09-24-2007, 08:46 PM
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Another great aspect of the HDHR that is sometimes overlooked is that it being networked allows you to locate it anywhere. This helps in a few ways: 1) it eliminates a heat source within your case, 2) it removes a lot of wires from behind your HTPC, 3) it allows you to locate the tuner closer to your antenna/cable feed, reducing signal loss. In your case, you could have HDHRs, one located by your cable feed and another located by where your antenna comes into your home.
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post #10 of 22 Old 09-28-2007, 05:56 AM - Thread Starter
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The HDHomeRun sounds like what I want. The price is cheaper than buying 2 separate tuners. It frees up the limited (4?) PCI slots in a MicroATX box. It also removes a heat source from the case. It also allows me to view/record HD on my living room TV with Myth backend/frontend box as well as a Vista Laptop and/or XP PC in my office bedroom upstairs (I inquired about a Windows front end that would work with Myth, but don't think there was a workable solution).

However, I'm confused as to SiliconDust's claim that it is a 100baseTX high speed network. Does that mean that it simply will connect to a network since it only has 1 ethernet port? If I want to connect it to more than one computer, I will need to connect it to a switch, right? I was planning on buying a 4-port cable router to share my cable modem among my bedroom PC and Myth box in the living room (for ScheduleDirect info) as well as a laptop and second or third PCs. If I were just using 1 HDHomeRun, I guess I would just plug the ethernet cable from it to the Myth box, but if I want to share it with another PC, I would need to hook it up to another switch (separate from my cable modem router)? Also, if I share it with another PC, would the PC be able to tune different channel(s) than what the Myth box is tuning?
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post #11 of 22 Old 09-28-2007, 06:26 AM
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That just means that you connect to it via ethernet. Plug it into a switch so that you can connect to it from more than one computer. For example, I have mine plugged into my switch. It grabs an IP address from my DHCP server (or in your case your cable router). My Mythbox is what typically connects to it to watch/record TV. I also connect to it with my laptop to run the utilities to update the firmware, etc. Additionally, I occasionally connect to it with my laptop to watch TV on my laptop. The HDHomerun has 2 totally different tuners, so two different computers could use it at the same time. If you do the tuning through MythTV, the backend would handle routing each mythbox to the proper tuner. If one of the computers is non-Myth, you could look at the status lights on the HDHR to determine which tuner is in use by the mythbox and direct the other computer to the idle tuner.
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post #12 of 22 Old 09-28-2007, 07:58 AM - Thread Starter
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Ok, so it sounds like I can hook up the HDHR and Myth box and a Vista laptop (and maybe even an XP PC) all to a cable router instead of having to buy both a cable router and an ethernet switch. I'm going to start out with 1 HDHR and have my antenna hooked up to one tuner port and cable hooked up to the other tuner port. I won't be able to tune 2 OTA or 2 QAM simultaneously until I buy a second HDHR, but I'll work with this setup for now.

drkdiggler, have you tuned into the HDHR on the same tuner with your laptop while your Myth box is tuned in on the same tuner? Also is your laptop running Myth front end, or Windows? From the https://www.silicondust.com/forum/viewtopic.php?t=4165 sounds like I can have my Myth box and living room TV tuned into, say, the local noon news Channel 7 OTA, then go upstairs to work on my Vista laptop in my bedroom and decide I want to watch the same news while working on my laptop (or other computer in my bedroom), and tune in to OTA Channel 7 on my laptop using the same tuner. If, during a commercial, I change to OTA Channel 9 news, that will probably also change the TV hooked up to the Myth box to Channel 9, but that's ok. As long as I'm not recording anything on that tuner, it won't really screw anything up unless Myth gets confused by the channel changing without it changing itself. If you can confirm that one tuner can be shared by 2 computers and viewed at the same time, please let me know. Also, would be nice if you can confirm that this works with different OSs (specifically Myth and MCE in my case).
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post #13 of 22 Old 09-28-2007, 08:08 AM
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I haven't specifically tried to connect to a tuner that is already in use. I'll give it a whirl.
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post #14 of 22 Old 09-28-2007, 02:05 PM
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In MythTV you don't actually watch the live feed from the tuner. MythTV records everything, even live TV. When you watch "live" TV, you are actually watching the recording of the capture card feed. If you want to watch a program that is being shown "live" on another frontend, go to the recorded programs section and select the show.

In order to see the live TV shows in the list, you must first enable it in one of the setup screens.

Another thing, you mention buying a cable router. If you already have a cable modem, all you need is a regular router. It will be much cheaper. I have both a router and a switch. The router feeds the switch. If I want one of my computers to be accessed from the internet, I hook it directly to the router, and then configure the router to allow it.
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post #15 of 22 Old 09-29-2007, 10:41 AM - Thread Starter
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A friend told me I need to make sure the router I buy is a cable router. I'm not really sure what the difference is - I guess a cable router has a coax cable input and a regular router only has an ethernet input jack. My Comcast rented cable modem has an ethernet jack as well as the coax jack. I'll probably buy my own cable modem to replace that sometime (should have years ago - I'm sure the $3/month rental fee would have already paid for several modems). With 2 ethernet jacks for by a Myth box and HDHomeRun, and another for the cable modem, that leaves only one more for my computer in the bedroom if I buy a 4 port router. I probably need an 8 port router if I'm going to want to be able to hook up an additional computer, and maybe a 2nd HDHomeRun.
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post #16 of 22 Old 09-29-2007, 01:41 PM
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I didn't realized you had to rent your modem. I have Time Warner cable, and the modem has no additional cost, though I most likely paid for it with my installation fee.

Just make sure your modem is compatible with the Comcast system. Check with them to see if some are and some are not.
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post #17 of 22 Old 09-30-2007, 12:19 AM - Thread Starter
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Quote:
Originally Posted by h_a_h_3 View Post

The HDHR (there's only the one by that name) is not a "card", it is a network attached device. This device has two independent digital (ATSC/QAM) tuners, each with a single coax input, along with an IR port for remote control and the network connection. So it doesn't take any slots or USB ports away from your computer.

To achieve your goal of dual ATSC or dual QAM recordings, perhaps you should buy two HDHRs so you won't have to remember to flip an A/B switch depending on recording schedules - actually this would enable dual ATSC *and* dual QAM recordings simultaneously. Each stream to the PC is up to 20Mbit/s, so four should fit on one 100Mbit/s connection; or you could run each HDHR into its own network card on the PC if you feel like it. Gigabit switching and gigabit on the PC should also be more than sufficient.

Is the bandwidth of a router or switch cumulative? Does a router rated at 100Mbs have total throughput of 100Mbs available to all it's connections, so that 2 HDHRs take up to 20Mbs each, leaving 80 Mbs to the rest of the ports? I had previously thought that a 10/100 rating means each port is good for up to 100Mbs so one could have 2 100Mbs devices opertating at 100 Mbs each.
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post #18 of 22 Old 09-30-2007, 06:10 AM
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For all intensive purposes, the bandwidth of each port on a switch is independent (neglecting the backplane which is cumulative I believe). To cover your question, each HDHR would have a full 100 Mbps to itself, with one caveat, each HTPC or backend is (typically) on a single port. So, if you have a single HTPC and 3 HDHRs, each HDHR gets a full 100 Mbps, but the HTPC is limited to 100 Mbps on its port, so you couldn't stream from both tuners on all 3 HDHRs to the HTPC, despite each one having a full 100 Mbps to itself. On the plus side, Gigabit hardware is cheap enough that you can avoid these concerns.
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post #19 of 22 Old 10-02-2007, 01:15 AM - Thread Starter
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It sounds like a router or switch's backplane is cumulative. However, I assume that means that a 4-port router with 10/100Mbps ports should have total capacity of 400Mbps (4x100), not 100Mbps (100Mbps max divided by 4). h_a_h_3's statement had me believing the latter, but after re-reading again and again, I think he is referring to the 100Mbps connection on the Myth box, not the router.

A friend just gave me an 8-port Linksys switch and claims that he was able to use it to share a cable modem. I thought a router is required to share a cable modem since the address provided by a router is needed to share the cable modem. I had planned on buying an 8-port router, however, if a switch will suffice, that's more $ savings.
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post #20 of 22 Old 10-02-2007, 04:10 AM
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Yes, on larger switches the backplane is not always large enough for all of the ports to simultaneously operate at full speed. I wouldn't expect you to be able to share your cable modem with only a switch unless the cable modem itself was either: 1) acting as a router (some do this); or, his cable service allowed more than one IP address, so the cable modem was handing out an external IP address to all of your friend's computers.
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post #21 of 22 Old 10-03-2007, 02:57 AM - Thread Starter
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Quote:
Originally Posted by drkdiggler View Post

I haven't specifically tried to connect to a tuner that is already in use. I'll give it a whirl.

Were you able to do that from your laptop? Are you viewing from your laptop with Myth on Linux or Windows MCE?
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post #22 of 22 Old 10-03-2007, 04:25 AM
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If you connect to a tuner that is already in use, you take over the stream and it stops sending to your mythbox. For viewing I was using the "HDHomeRun Config" software that comes with the HDHomerun. It lets you pick a tuner and watch TV using the VLC player. If I am not mistaken, you can install this on any of the modern versions of Windows (Vista, XP, 2000).
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