[mythtv] broken nuv file

[Torbjörn Jansson]

Hello all.

I've run into something odd with one of my recordings.
This is on 0.21-fixes branch and a recording done on an old analog card.

First thing I noticed was that when playing the recording on the frontend
seeking didn’t work.
Any kind of seeking resulted in playback stopping.

After some analyzing of the resulting nuv file i think I've found out what
have happened to the file or atleast part of it.

First problem:
The offset to the seektable stored at the beginning of the file does not
point to the right place (offset should be larger by about 68705 bytes)
This in itself is bad.

After some more analyzing of the file I found the cause.
2 extra video frames (or packets, header + data) have sneaked in and it is a
repeat of the 2 previous video frame/packet.
There is also some repeated audio frames in there.

The amount of extra data matches exactly the error in the offset to the
seektable.


I'm no expert of the mythtv source so I have no idea where to begin looking
for the bug.
What I do know is that the setup I have have worked fine until recently and
the only difference now is that the backend have a little more load because
of other software including disk io.
(same for the nfs server where the recordings get saved to)

Any idea what caused that extra data to sneak in?
I had to manually fix this file and it's a little complicated to do it so
would be nice to avoid it :)

So far I've only seen this once but i think the current one may have similar
problems, master backend crashed shortly after slave backend started the
recording.