Different channels on different tuners (MythTV)

My SiliconDust HD HomeRun has a relatively good HD tuner, but it’s not quite as good as the built in tuner on my TV at picking up stations that are extremely strong and have multi-path reception problems. Although the signal My MythTV box reception of Fox TV would intermittently cut out as the SNR would drop too low to enable reception (even though, or, because the power level was pegged at 100%).

I purchased a Skywalker 16db attenuator, and it successfully lowered the signal strength of the (overpowered) Fox channel so that my HD HomeRun’s tuner chip could receive it with an acceptable SNR and no dropouts.

The only problem with attenuating my signal was that one of the two PBS channels (8, GPB-HD) was too weak to be picked up through the attenuator.
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Daylight Savings Time MythTV wakeup failure

When I set up my MythTV box to suspend itself (and wake up whenever a show needed to be recorded) I followed the directions on the MythWiki ACPI Wakeup page, which suggested that I disable writes to the hardware clock as follows:

“Disable hwclock updates

On most machines it’s required to make a small change to the Linux shutdown procedure. When your machine goes down, most linux distributions write the system time/data back to the bios. On MANY machines, the machine never wakes-up after a time/data update. It’s recommended to make this change before you start. See below for more details (distro specific),

The reason for the recommendation above is that most linux distributions write the current system time back to the bios when shutting down the machine, and with some BIOSes, the machine will not wake up if the hardware clock is modified after the alarm timer has been set. To avoid that, it is necessary to disable the writing of the current system time to the hardware clock in the system shutdown scripts.”

This had no negative effects until daylight savings time kicked in. My MythTV box syncs itself over the internet, so it updated itself to daylight savings time with no problems. However, the system BIOS clock (hwclock) was not updated because I had disabled hardware clock updates! After a week of recording the very ends of shows instead of the full shows, I figured out what was happening and issued a “hwclock –systohc” command to re-set the BIOS (hardware) clock from the (correct) system time.

However, this will only work until daylight savings time ends, so I am investigating if I really need to disable the write to my hardware clock after the system sets the wakeup time. It may be that my BIOS handles that correctly, in which case I can take out the “HWCLOCKACCESS=no” line I added to my “/etc/default/rcS” file.

MythWelcome Menu / GUI slowness

On my 0.21-release-fixes codebase, MythWelcome would pause for a long time (2-3 seconds) after I pressed the “MENU” key before making the menu pop up. This was because a call to “mythshutdown –status” was taking several seconds to return, and MythWelcome waited for the return value of that message before drawing the menu (It wanted to know if it should draw a “unlock” or a “lock” button.)
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MythTV power conservation

Our MythTV entertainment system uses a decent amount of electricity. While watching TV, the television, DVD/Amplifier and computer (plus misc other items) use 335 watts of power. However, as we only average an hour or two of TV a day, this isn’t as large as the continuous power draw from the system when it is not in use. Even though we turn the TV and DVD/Amplifier off when not in use, the computer, HD Tuner, external HD, antenna preamplifier, printer, etc take up 141 watts when idle, and around 160 when recording, trans-coding, or detecting commercials in a television show. As the MythTV computer runs 24/7, this adds up to just over $10 a month of electricity (101 kW/h).

In an effort to save power, I have configured the MythTV system to shut itself off when idle, and wake up automatically five minutes before the next television show it is scheduled to record. This saves power, but has the major downside that the computer is not running and instantly ready whenever we want to watch TV. If the MythTV box isn’t already awake recording a show, you have to manually push the power button and then wait for two minutes while it boots up and gets itself ready. We are no longer able to press the TV-Power button and start watching TV five seconds later. However, this saves about 105 watts whenever the system is off (about 20-22 hours a day), or about $75-$84 a year.

We still have a constant drain of 36 watts, even when the system is turned off due to various peripherals and parasitic power drains.

  • The UPS & Computer, even when turned off, takes 10 watts (Mostly the UPS keeping its battery charged).
  • The external USB Hard Drive takes 8 watts.
  • The printer takes 6 watts when in standby mode.
  • The DVD/Amplifier, even when turned off (in standby mode) takes 5 watts of power.
  • The HDTuner (Silicon Dust HDHomerun) takes 5 watts of power even when idle.
  • Various other items (PDA charger, External Antenna pre-amp power injector, TV when off) take a watt each.

With the exception of the 10 watts from the UPS/Computer, the other power draws could be eliminated by using a “master-controlled” power-strip (such as the APC P7GT), which automatically turns off the controlled outlets when the computer (plugged into the master outlet) is turned off. This would save 26 watts whenever the computer was turned off, and would save about $20 worth of electricity in a year, paying for the fancy power saving power-strip in less than two years. Also, if I replaced the UPS with a “green” version, it would take less than 10 watts to keep the battery topped-up, but that cost savings would take longer to pay for itself.

Silicon Dust replacing HD Homerun power adaptors

Back in January the power adapter failed for my Silicon Dust HD HomeRun (a network HTDV tuning device).

They replaced my power supply and claimed that they were seeing only a 1% failure rate. As late as March 28th they were sticking to the "less than a percent" figure. Eventually on June 3rd they posted an offer to replace all SW20-S050-15 power adapters.  Unfortunately for me, they did not send an email to all customers, so I did not find out about this until my power adapter failed (today) and I went to submit a trouble ticket and saw the notice.  I guess that "1%" were causing them a lot of problems…

I've been very happy with the HD HomeRun unit itself, but once again, the el-cheapo power adapter is my weakest link and is keeping me from watching TV until the replacement arrives (and since it happend on a Friday, I'm probably without TV until next Wednesday at least).

So, if you have a HD HomeRun with one of the older adapters, head on over to the replacement page and order a replacement before yours dies.  (So far the forums haven't listed any fires started by the failing power adapters, just dimples of melted plastic on the side due to the failure, so hopefully they are not dangerous.)

MythTV / MythDVD movie ripping / playback problem (Solved!)

I have used Myth to rip a large number of my DVD's to AVI files (using either the Excellent or Good setting).  Now that I am starting to play back the movies, I have found something that is very troubling.

On many of the movies, the first 95% of the movie (e.g. 1:13 min of a 1:26 movie) plays flawlessly. However, near the end of the movie, the audio and video starts to speed up and get jerky. (Audio/video sync is also thrown off.) Continue reading

DPMS monitor control via remote control on Myth TV

I am using an LCD monitor as the display for my MythTV box, connected via an analog RGB (a.k.a. VGA) cable. This allows me to use DPMS (Display Power Management Signaling) to turn the monitor on and off from the MythTV box.

Instructions for setting this up with MythTV are here , but I found that I had to make a few changes to get things to work correctly. I modified one line of the shell script  as follows:

STATUS=$( xset -q | grep "Monitor is" | awk '{print $3}' )

To trigger the monitorpowerbutton.sh script, I placed the following into my /etc/lirc/lircrc file:

 prog =  irexec
 button = TV_POWER
 repeat = 4
 config = /usr/local/bin/monitorpowerbutton.sh

Now my TV_POWER button toggles the power state of the monitor!