Mythtv

[mlord]

In an ideal world, our MythTV box would have a fanless 9600GT card --> twice the number of shaders as the 9500GT, and faster clock rates too.

This would give enough horsepower to really take advantage of VDPAU extras, like inverse telecine on HD content, and noise-reduction + sharpening for analog OTA content.

As it is, I *do* use those features sometimes, but they also do cause the odd skipped frame here and there. A 9600GT would cure that, and then some.

But.. alas.. I don't think any of the available fanless 9600GT cards would actually fit inside Duke's chassis. So the existing Sparkle 9500GT (1GB,fanless,small) will just have to do.

But if fanless is not a high priority, then there are lots of more powerful cards that ought to fit in any case. Should you actually decide to ditch that crappy 8500GT card, I might even offer you a few bucks for it.. if it is fanless.

Cheers

[stampeder]

Yep, my 8600GT has a fan, as it audibly reminds me every time I power on the myth-frontend box.

I'll have to check inside that box for video card space because I'm pondering something like a GeForce GT220, which offers complete VDPAU-based acceleration for MPEG-1, MPEG-2, MPEG-4 Part 2 (a.k.a MPEG-4 ASP), VC-1/WMV9 and H.264 and can be found for relatively cheap these days.

[roger1818]

Instead of going fanless, has anyone considered going water cooled? That should be significantly quieter than fans and keep things much cooler.

[Daemons]

Originally Posted by roger1818

Instead of going fanless, has anyone considered going water cooled? That should be significantly quieter than fans and keep things much cooler.

Water cooled is not fanless. You need a big fan at the back to cool the radiator for water cooled systems. That and it's quite expensive. Best kept for gamers in need of more "bling" for their pimped up PCs.
The HTPC market needs has brought forth some very good fanless video cards, and some are low profile which is great for those who need them in micro cases.

Marc

[Daemons]

Is there a signal meter in MythTV 0.22? I can't find one in 0.21

Actually, I've only found utils to scan for channels, but none for signal metering. What do you guys use to line up you antenna and tune your reception on Linux/Myth? I can't bring my 32" HDTV up on the roof. It's not very portable.

Marc

[mlord]

There's a signal meter for (most) digital tuners, but I don't see one for analog. I've long since hacked the digital one on my system here, to show an extra decimal point as well as the raw value from the hardware (rather than only the cooked "dB" number from software).

To get the signal monitor, use Edit Keys to assign signalmon to a button on your remote control.

Cheers

[Daemons]

Originally Posted by mlord

There's a signal meter for (most) digital tuners, but I don't see one for analog. I've long since hacked the digital one on my system here, to show an extra decimal point as well as the raw value from the hardware (rather than only the cooked "dB" number from software).

To get the signal monitor, use Edit Keys to assign signalmon to a button on your remote control.

I think I could use that hack. I have an HVR-1600.
I found signalmon under Edit Keys, TV Playback (0.21). It was assigned Alt-F7. I changed it to another key, but it still doesn't do anything. I must be missing something. I want to use it to line-up my new antenna.

Edit: Ok. I got it working, sort of. Signal is always 0% and S/n at 2.3-2.4 but I have a picture. Must need to be hacked to work on the HVR-1600 or something.

Marc

[mlord]

Yeah, that's "normal" for the cableTV-centric MythTV stuff.

Signal-strength always reads zero for the HVR-950Q as well as the HVR-1600 here, with both of those showing SNR instead.

The HDHomerun shows signal-strength, but not SNR.

In my experience, the SNR must be greater than 2.2dB for reliable HVR-950Q reception, and greater than about 2.28dB for the HVR-1600.

[mlord]

Originally Posted by mlord

I've long since hacked the digital one on my system here, to show an extra decimal point as well as the raw value from the hardware (rather than only the cooked "dB" number from software).

Originally Posted by Daemons

I think I could use that hack.

Here's the hack (source code patch):

--- old/mythtv/libs/libmythtv/tv_play.cpp       2008-12-31 10:16:04.000000000 -0500
+++ new/mythtv/libs/libmythtv/tv_play.cpp       2008-12-31 17:10:57.000000000 -0500
@@ -5411,8 +5411,10 @@
     QString sigMsg  = allGood ? tr("Lock") : lockMsg;

     QString sigDesc = tr("Signal %1\%").arg(sig,2);
-    if (snr > 0.0f)
-        sigDesc += " | " + tr("S/N %1dB").arg(log10f(snr), 3, 'f', 1);
+    if (snr > 0.0f) {
+        sigDesc += " | " + tr("S/N %1dB").arg(log10f(snr), 4, 'f', 2);
+        sigDesc += tr("(%1)").arg(snr);
+    }
     if (ber != 0xffffffff)
         sigDesc += " | " + tr("BE %1", "Bit Errors").arg(ber, 2);
     if ((pos >= 0) && (pos < 100))

[roger1818]

Originally Posted by Daemons

Water cooled is not fanless. You need a big fan at the back to cool the radiator for water cooled systems.

Not necessarily. You can get fanless water coolers that use a large heat-sink outside the case as a radiator. Although you can get fanless video cards and large heat-sinks for your CPU, without fans (or a water cooler) the problem is there is nothing to get that heat outside of the case quickly (it will slowly convect out the ventilation holes) so heat will build up, reducing the effectiveness of the heat-sinks.

[mlord]

Stampeder, please give us all an update on your MythTV-0.22 experiences to date. I imagine I'm not the only one curious about how things are working out there!

Cheers

[stampeder]

Its a bit complicated right now due to some personal time contraints, but I was running 2 pcHDTV PCI ATSC cards with 2 H150 NTSC analogue cards and 2 950Q USB ATSC devices. I've pulled out the 2 pcHDTV cards for now to better assess the 950Qs, but I'm finding that the pcHDTV cards (Generation 5 chipset) lock onto the signal more quickly and require less signal strength than the 950Qs (Generation 6). I would have expected the opposite so I have more testing to do. In the real world this means that ATSC Live TV on the mythfrontend box seems to be hit and miss as a result. This was never a problem with the pcHDTV cards so I'll be putting them back in. OTOH all test recordings made with the 950Qs have been excellent.

So, its not really about the MythTV 0.22 software, its about my own hardware testing. I'm quite pleased with 0.22 actually.

[mlord]

Any idea what the noise factor (NF) is for the pcHDTV cards?
The 950Q claims 5dB there.

Cheers

[roger1818]

The generation of the decoder chipset is only one piece of the puzzle. Tuner sensitivity is another. The higher generation chipsets will handle various types of interference (including multipath) better. For weak signals, the tuner sensitivity becomes more important. Maybe the pcHDTV has a better tuner than the 950Q.

You could always use both the pcHDTV cards and the 950Qs and configure the backend to use the pcHDTV cards for live TV and your weak broadcasts and the 950Q for recording the stronger stations.

[stampeder]

roger1818, yep, MythTV allows you to prioritize the input devices and that's what I've done in the past. I think you are correct about tuner sensitivity, but I'm in a great location for the Mt. Seymour stations so to me it is very odd that the 950Qs are not performing as well as the pcHDTV cards.

mlord, I haven't gone on the pcHDTV forums in quite awhile (product hasn't changed in about 3 years) but I'll take a look in there for NF data and maybe email Jack Kelliher for that info if need be.