[mythtv-users] Live TV broken?

[Raymond Boettcher]

Hoi Chris,

Thursday, January 1, 2015, 1:11:36 AM, you wrote:

> Thanks to all who replied.  I think I've nailed it.  I have a
> switch between my mythtv box and my HD Homerun that is negotiating a
> 100MB connection instead of a gigabit connection.  That switch has
> the HDHR, 5 surveillance cams, an xbox and several other machines
> running through it.  Looks like I have a physical cable problem
> somewhere.  When I disconnect everything except the HDHR, my
> recordings and LiveTV clear up because there's not much network activity.


> On Wed, Dec 31, 2014 at 3:50 PM, Jay Foster <jayf0ster at roadrunner.com> wrote:

> On 12/31/2014 1:43 PM, E James wrote:
>  
>  On 31/12/2014 02:20, Chris Gentle wrote:
>  
>  Within the last couple of weeks, my Live TV has started breaking
> up and distorting really bad.  I'm not sure exactly when it started
> but it has become unwatchable.  I do over-the-air only and have
> really good signal strength (90+) coming into my HD Homerun.  I
> bypassed the HD Homerun and hooked a TV straight to the antenna to
> verify that the signal is good. No artifacts in the picture at all. 
> Also switched out the HD Homerun with a spare one but that didn't make any difference either.
>  There have been no hardware changes in my myth system in months.
>  
>  I did a completely fresh installation of Mythbuntu 14.04.1 today
> just to see if that would make a difference but it did not.  The
> problem persists even after a reinstall.  I recorded a show, copied
> the recording to another machine and played back with mplayer.  The
> recording itself is bad.  The artifacts show up in the recorded file
> so I think I've narrowed the problem to the recording phase rather than playback.
>  
>  I'm not sure what to look at next.  Any suggestions?  Any new known problems with Live TV?
>  
>  Version Info:
>  
>  MythTV v0.27.4-27-g40506c3
>  Mythbuntu 14.04.1
>  nVidia GeForce 210
>  nVidia driver 331.113-0ubuntu0.0.4
>  
>  Thanks.
>  
>  -- 
>  Chris
>  
>  
>  _______________________________________________
>
>  I have a Shuttle DS47 running Lubuntu 13.10 and MythTV .27
> combined BE/FE. The monitor is an LG monitor / tv and MythTV uses 1
> HDHomerun to receive the 2 main Freeview multiplexes. I recently
> discovered that some of the MythTV gui pages seem to generate
> interference which upsets reception on the BBC multiplex for both
> the TV and the HDHomerun. More details if requested. I am
> considering using a frontend on a different PC to eliminate the
> problem but it seems to require more MySQL expertise than I currently possess.
>  _______________________________________________


>  The OP subject says, "LIve TV" is broken.  Is it only live TV or
> are recordings breaking up too?  If both, then I would suspect the
> HDHR power supply.  I have had several go bad.  I could still ping
> the HDHR and sometimes tune channels, but it would drop out while
> recording.  One of the bad ones was so hot that it burned me when I
> unplugged it.  Lucky it didn't start a fire.
>
>  _______________________________________________


> First, try always to post at the bottom of the list! :)

> Next, if you have a free pci-e slot in your machine, I suggest getting
> a simple network-card and lay in a dedicated line between the homerun
> and the backend. That way you prevent these kind of disturbance!

> Tot mails,
>  Hika                            mailto:hikavdh at gmail.com


Hey Chris,

His solution of course is the best and most guaranteed way to ensure that doesn't happen again.  Also, depending on the Network Controller, you may have to use a cross-over cable to directly attach the HDHomerun to the second network card (or have another network switch handy) in your mythbackend and run on a seperate subnet and DHCP Server for that network card so the HDHomerun can obtain an address and use the second link (You will have to reconfigure MythTV for the new IP Address of the HDHomeRun).  You could bridge the 2 network cards together using brctl but that gets a little more complex but maybe easier than configuring a separate subnet and DHCP Server just to link up the HDHomeRun and still offers the benefits of a dedicated connection between the HDHomeRun and the Mythbackend while allowing you to use your existing network, DHCP Server and all...  Many people aren't running their own dedicated DHCP Server and often use the DHCP Server on their hardware router.  They enter MythTV-setup and select the Network Tuner and MythTV detects and does the rest.

I had the same problem and it was due to a bottleneck in my network as well.  My HDHomerun links at 100mb, but in my instance I swapped the 100mb switch for a gigabit switch.  Made sure the backend server is connected to that switch and it is linked at gigabit! (dmesg will say or the light on the network controller or switch will be Amber instead of Green or visa versa)  Some on-board controllers support gigabit, some don't.  I have a dedicated Intel PCI-E Gigabit Controller and it does the trick without issues.  Also, make sure the HDHomerun is connected directly to that switch and not 1-2 switches down the line causing some other bottleneck.  That is the alternative solution.  In theory that gigabit connection should handle the full bandwidth of 10 x 100mb links to that switch all talking to the mythbackend at the same time.  Unlike hubs, switches will convert the signaling from 100mb to gigabit while it's passing through the switch.  That doesn't mean you will get more bandwidth from the 100mb link as it does just the opposite going from the gigabit to the 100mb link.  But it will ensure that you have as much bandwith as possible between the switch and your server for the camera links, HDHomeRun, etc.  

Make sure your hard drive is not the bottleneck...  If the drive light is lit solid, this is likely the issue.  If you are recording those camera's onto the same hard drive as your DVR Recordings, the drive may not keep up.  This will create a lot of seek time and fragmentation between the recording(s) being saved and the 5 camera's recording to separate files on the same disk.  It is VERY wise to give MythTV it's own drive, separate of the OS, or any Camera Feed recording you may be tossing at that machine.  The drive will likely get very hot and fail much quicker if you run the setup all on 1 drive.  Especially if you are pulling a full 30fps from each camera.  If they are security camera's, dial them down to 2-3 Frames per second.  This will greatly conserve network bandwidth, disk space and possible drive failure.

Even if they are being recorded on another machine...  Dial down the frame rate anyway mainly because of the network bandwidth being used.  Or connect that Camera Recorder machine and cameras to a separate network switch.  You can still connect the switches together, but it will keep camera bandwidth and recording limited to 1 switch while the other switch handles DVR Recording (MythBackend), Frontend Access and HDHomeRun access...  Make sure both switches are gigabit and that they link to each other at gigabit speed.  Technically 1 big switch (16 port, etc) can handle it, but this makes your layout easier to understand...  Generally two 8 port gigabit switches is cheaper than a 16 port gigabit switch, however the 16 port switch does give dedicated bandwidth to each port without bottle necking the link between the two 8 port switches.

CPU bottleneck could also be an issue if the program used to record the camera feeds is transcoding the feed live before saving it to disk.  Many IP Camera's send out MJPEG Frames and it's often wise for the program to convert that to a "more space saving" format.  If you are using ZoneMinder, it tends to create millions of JPEG files on the disk which also creates a lot of activity for your hard disk...  I highly recommend using a separate machine for handling the Camera Feeds, especially if they are HD IP Camera's.  It can be done on 1 machine cause I've done it, but careful planning over computer specs, program settings (MythTV and the IP Camera Recorder), network bandwidth, etc must be taking into account...

This option is a little more economical if you don't have spare ethernet controllers laying around and/or your not versed on how to configure a "small network" while using MythBuntu Linux as the "Host" (IE: DHCP Server and perhaps Gateway if needed) of that "small network."  MythBuntu is pretty stripped down, and will require installation of some packages to make everything happy.  And if you use Windows as your mythbackend host, that makes matters twice as complicated.

Anyhow, keep that in mind.  This community is extremely versed on hardware configuration, linux/windows administration, programming, etc.  It's REALLY easy to say things like "setup another network card" but it's easily missed that the person may not know how to or what is involved in doing so.  And as you can see from above, that may not be the problem.  But he is right, it is the most likely problem.  You may know all of this already but I wanted to point out what is involved anyway because some people don't know and it's easy in a Tech Forum to speak "Tech" without first finding out the skill levels of the person that the question is being answered for.  MythBuntu is generally the version people install that want to "get their feet wet" with MythTV, but don't really want to jump into the deep end and figure out if they can swim or not (Compiling code, Customizing MythTV, etc).  Linux is hard to learn, trust me, been there, done that...  Started with RedHat and ended with Slackware.  I hope this helps...
-RayRay-
  
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