[mythtv-users] picture freeze

[f-myth-users at media.mit.edu]

    > Date: Mon, 28 Sep 2009 20:23:33 -0600
    > From: Jerome Yuzyk <jerome at supernet.ab.ca>

    > This evening I missed most of the first half of Monday Night Football (via 
    > TSN on Shaw Cable in western Canada) (started recording 1.5 hours before 
    > watching) because the picture simply froze. It unfroze at the beginning of 
    > the half-time show and so far seems ok. This has happened before with TSN. 
    > I am wondering if it's a TSN problem (their feed froze), or a problem with 
    > my machine/database (a tuner is going wonky or something).

This was a total freeze of the video with silent audio, right?

    > Any ideas or similar experiences?

I have no idea about your showing in particular (I neither watched
it nor am I in western Canada), but this sort of thing happens very
frequently on my cable feed.  I'd say that at least once a month
something simply freezes for seconds to hours, with very high
variance---one of my PBS outlets used to do this several times
a night a couple times a week; others are clearly screwups doing
ad insertion, etc.  Just last week I had 2 out of 3 simultaneous
recordings simply drop their video and go to silent audio for about
four minutes, whereas the third one was completely unaffected---
clearly different paths to (or within) my cable provider.

In my case, frozen video is always the provider, but I have a very
simple setup that records SD from PVR-250's from STB's, so there's
little else that can freeze but not fail.  (If the STB loses signal,
it freezes for an instant and goes to black, followed by its channel
description for a couple of seconds when the signal comes back.  If
the cable company screws up, it either goes -instantly- to black,
without a freeze, or it freezes and -never- goes to black.)

One thing that made it easy for me to diagnose was that not only did
I see identical behavior if multiple tuners were staring at the same
feed (e.g., if it happened during the overlap during back-to-back
recordings that each had pre & postrolls), but back when my feed was
analog (and hence I could record most of my channels directly off the
wire), I could see it directly on the attached TV, or on a TiVo if it
was looking at the same signal, etc.

One way of at least figuring out whether you've got a hardware
problem or a provider problem might be to try running the code in
http://svn.mythtv.org/trac/ticket/6899; I'd be interested in your
feedback if you try it.  It will warn you if the audio track drops
dead; you'll get the warning essentially the instant it happens, so
if you happen to be around, you can try flipping a TV to the same
feed, or starting a second recording on an available tuner, or even
rebooting the box if that's your only way to try again, etc.