[mythtv] SVN issues

Daniel Kristjansson danielk at cuymedia.net
Sat Dec 3 15:06:58 EST 2005

On Sat, 2005-12-03 at 20:28 +0100, Torbjörn Jansson wrote:

> I created a few "No signal" pngs and i managed to regenerate the dummy
> streams with mkdummyts.sh.
> I used mythfrontend to tune in to an encrypted channel and for a short while
> i was able to see my green "No signal" text for a short while and then the
> frontend exited livetv with "Error was encountered while displaying video"
> and when i pressed the OK button in to get rid of the error message the
> screen when all black.
Hmmm, I'd need a backend log with record,channel and frontend log with 
playback,file to try to figure out what went wrong here.

There is still a problem with ring buffer switching that I haven't
tracked down, but it seems if we enter the prebuffering pause in
the NVP before the any frames have been decoded the frames never
get decoded.

> I added a few VERBOSE outputs in the dummy recorder so i could see what file
> it used to create the dummy streams and this is what it said: "DummyRec:
> Using /usr/local/share/mythtv/themes/default/dummy768x576p50.00.ts"
> I don't know if this has anything to do with the frontend exiting or not,
> but the display on my epia frontend is 720x576
Not a problem, this is the video resolution. So long as you can
play a video at that resolution there shouldn't be any problem.

> I experimented a bit with ppmtoy4m and changed -n15 to -n150, i asume this
> is the number of frames in the dummy stream,

> the windows demuxer & mpeg2 decoders was much happier and i no longer get a
> messed up video when playing the dummy stream from the backend.
> I'll do some more tests and see if i can get it to work with less frames.
The problem is probably that they can't deal with the MPEG timestamps
resetting so often. We loop the video once we get to the end; And I
set the stream length to be just long enough to not cause problems with
ffmpeg or libmpeg2.

BTW If you are using the Microsoft Media Player library it has many,
so many, I mean incredibly many, nay insanely many, problems decoding
MPEG streams. I highly recommend using any other decoding library.

> For some reason when i was experimenting with the dummy streams i managed to
> get the backend to create around 160 zero length files in a very short
> period of time, at the time i had "-v record" on the backend and this was
> repeaded over and over in the log:
> 2005-12-03 16:12:05.191 Preview Error: Previewer file
> '/mnt/store//20347_20051203161204.mpg' is not valid.
Hmmm, does your record file prefix end with a slash "/" character?
If so I'm surprised you can make recordings at all.
It's probably something we should check for...

> 2005-12-03 16:12:06.231 WriteStringList: Error, writing to unconnected
> socket.
The backend probably died somehow if the you are getting these on the

> It's not fun to delete 160 recordings using mythweb and waiting for the
> backend to timeout trying to generate all the preview images takes for ever.
> But maybe this is a completly different problem?
I think this is unrelated. I think it may just be that we don't strip a
trailing slash of the RecordFilePrefix setting before using it.

> I also managed to get a realy big segfault but unfortunately i didn't have
> gdb attached at that time so i don't have a backtrace.
Try to reproduce it and get a backtrace. Sometimes it is easier
to turn on coredumps and then just load that into gdb post-crash
to get the debugging info.

-- Daniel

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