[mythtv] dvb zero length record

[Phil Vid]

I'd just like to update everyone with my ongoing investigations into
the zero byte dvb recording phenomenon.

There appear to be 3 distinct causes of the problem:

1. Blank recording, nothing obvious in the logs case 1. This appears
to be a keyframe detection problem. The recordings enter the
ReadFromDMX() loop but silently exit as no keyframe has been detected.
The obvious symptom of this is the absence of the message 'DVB#x Found
keyframe' in the log. I will investigate this first as this is the
cause of 90% of my zero byte recordings.

2. Blank recording, nothing obvious in the logs case 2. Problem with
PMT/CAM or not authorised to view. The recording enters the
ReadFromDMX() loop but silently exits upon receiving scrambled
packets. Easy to detect with an additional debug line upon exit, after
fixing case 1 hopefully this case can be remedied with some additional
resends of the PMT.

3. DVB#x WARNING - No data received ... This one I'm not sure about at
all. It doesnt appear to be CAM related, have tested by replaying the
correct PMT back to the CAM upon receiving this error message.

Any ideas, especially on case 1, would be really helpful. I saw there
was some discussion from Jesper and William Uther regarding this issue
but I'm not sure what the outcome was. I'll start digging through the
MPEG specs now.

phil

On 5/3/05, David Whyte <david.whyte at gmail.com> wrote:
> Look for a thread titles 'Failed DVB recording' which started on the
> 7th April.  It had some diagnosis too.
> 
> Whytey
> 
> 
> On 5/3/05, phil.vid at gmail.com <phil.vid at gmail.com> wrote:
> > Actually, my bad. I've just got a couple of zero byte ones come up now with
> > the no data received message. I'll see if I can debug it further.
> >
> > phil
> >
> > ----- Original Message -----
> > From: "David Whyte" <david.whyte at gmail.com>
> > To: "Development of mythtv" <mythtv-dev at mythtv.org>
> > Sent: Monday, May 02, 2005 8:20 PM
> > Subject: Re: [mythtv] dvb zero length record
> >
> > I too get 0B recordings and have mentioned it to the list where a number of
> > others did. In our case, we needed to restart the backend to get the
> > scheduled recording to work, or just myth would more than likely work on the
> > next recording.
> >
> > It was obvious for us as the logs contained the no data received in 1 second
> > message. Perhaps yours is a different issue.
> >
> > Whytey
> >
> > On 5/2/05, Jesper Sörensen <jesper at datapartner.se> wrote:
> > >
> > > Phil Vid wrote:
> > >
> > > >I'm experiencing an issue with dvb recording zero length files. The
> > > >system contains two cards, It only occurs on the CA enabled card and
> > > >it seems to be random. It is not regular enough to reproduce
> > > >immediately, however after leaving the backend running for a few days
> > > >it tends to begin showing the problem.
> > > >
> > > >Tuning logs appear fine, the channels do not appear scrambled. Nothing
> > > >is in the log to indicate any obvious failure.
> > > >
> > > >
> > >
> > > I can't see anything obvious either. Could you try running the backend
> > > with "-v all"?
> > >
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