This one has me baffled. I have a remote frontend and when trying to watch livetv on two of my HD Qam channels, I get stuttering. The two channels are my local ABC HD feed and ESPN HD. Both are fine if I watch LiveTV using the frontend on the backend server. If I try to watch those channels with livetv on the remote frontend, it seems to be ok if I don't change to another channel. If I switch to another channel and then switch back it, those channels start to stutter badly.

I did a test and recorded a ESPN HD show on the backend, and when I watched the recorded program on the remote frontend it plays fine with zero stuttering. (I would assume this rules out Graphics Driver/subsystem problems on the remote frontend)

My LAN is Gigabit Ethernet so I don't think bandwidth is a problem.
The remote is frontend only.
The backend stores recordings on a ~500gig logical volume made up of two SATA hard drives.

I'm at a loss as to where to even start looking now. Considering how Myth livetv is basically watching a time-delayed recording, I have no idea why I have issues that only present themselves when watching those channels via LiveTV on the remote frontend.

Ideas of where to look next?

When you have a recorded show on your hard drive, it is not performing any write operations. Only read.

When youre watching it live, it must be writing to hard drive and then streaming it to you from the hard drive. The hard drive then has to keep up with the write while still streaming to you.

That seems to be the only difference I can think of. If you are watching it straight on the backend server, it might be that picture is displayed straight onto screen and written at the same time. But not being read off the hard drive.

This seems to be the scenario from what I can see in your post.

You might be able to sort it out by using faster hard drives, a ram drive or RAID arrays to improve performance of your storage.

If you rewind and play about 30 seconds behind live do you still have the stuttering?

MythTV still writes first then reads for playing "live" TV on the local machine. There is no such thing as a truly live display.

DonInTn, did you resolve this?

I have exactly the same problem. The really weird part is that i can start a recording on the backend and watch that during the recording, but LiveTV stutters like mad.


nitrogen, no, neither pause nor rewind helps the livetv stuttering.

Any ideas?

I did find a solution to my problem. This may be specific to the more recent Nvidia drivers. Presently running Nvidia driver .9746 w/ FC5 .2257 kernel. It worked for both the Geforce 6600GT that I had in it, and the Geforce 6200TC that I installed yesterday.

I noticed that when I watched 2 of my QAM channels (ESPNHD and ABCHD) that the processor would be pegged at 100%. I found that the xorg process was what was doing it. It only happened on these two channels, the other QAM channels the xorg process only used 4-10% of the processor.

Much research later I ran across the following post
http://www.gossamer-threads.com/lists/mythtv/users/241898?search_string=nvidia%20tearing;#241898

It suggested adding a line in the xorg.conf file in the "device" section as follows

OPTION "UseEvents" "True"

That in combination to making sure I wasn't using OpenGL in the mythfrontend: setup :tv: playback and unchecking the vsync options in the nvidia control panel for OpenGL, and my stuttering/tearing disappeared. In the nvidia control panel I still have vsync checked under XV section.

This also corrected a problem when if I tried to use BOB deinterlacing. previously if I used BOB, the screen would constantly hop up and down what seemed like 1 pixel. It's rock steady now.

Just thought I would share in case anyone else having these problems.