[mythtv] Bug? HD-3000 DVB driver timestamps

[John Patrick Poet]

On Tue, 19 Apr 2005, William Uther wrote:

>
> On Mon, 18 Apr 2005 23:16:30 -0600, John Patrick Poet
> <john at BlueSkyTours.com> wrote:
>
> > I switching from the V4L2 HD-3000 drivers to the DVB HD-3000 drivers on
> > Wednesday, 13 Apr 05.  While they seem to work fine, commercial
> > flagging
> > suddenly seemed broken.
>
> [snip]
>
> > To give you an example of what I am talking about, here is a list of
> > detected comercial markers compared to the actual position:
> >
> > detected        actual      difference
> > 0:07:51.09  --  0:08:20.09     0:29
> > 0:17:21.22  --  0:18:25.22     1:04
> > 0:20:26.16  --  0:21:42.16     1:16
> > 0:30:38.29  --  0:32:32.29     1:54
> > 0:33:55.23  --  0:36:01.23     2:06
> > 0:45:33.24  --  0:48:03.24     2:30
> > 0:49:25.05  --  0:52:27.05     3:02
> > 0:58:41.01  --  1:02:01.01     3:20
> >
> > It kinda looks to me like the commercial flagger is using the "real"
> > keyframe positions, but the seektable is off, so when played the wrong
> > part of the show is skipped.
> >
> > Any ideas why the seektable slowly gets more and more off with the DVB
> > driver?
>
> Interesting....
>
> This may be related to the recent fix for this:
>
> http://www.mythtv.org/bugs/show_bug.cgi?id=221
>
> discussed here:
>
> http://www.gossamer-threads.com/lists/mythtv/dev/121688
>
> Assuming I'm reading your 'actual' vs 'detected' the right way around,
> then if the system was detecting bogus picture start codes in
> DTVRecorder::FindKeyframes() then you'd see what you're seeing.
>
> There are a few ways to start debugging it:
>
> a)
>
> If you have a look at FindKeyframes() in libs/libmythtv/dtvrecorder.cpp
> you'll see a debug define:
>
> #define DEBUG_FIND_KEY_FRAMES 0 /* set to 1 to debug */
>
> Turn on that define and get a backend log as you record something.
>
> b)
>
> Apply the patch attached to the bug report above in reverse (patch
> --reverse) to current CVS.  See if the problem with DVB recording goes
> away.
>
> c)
>
> Try re-building the seek table with `mythcommflag --rebuild`.  While
> debugging bug #221, I found that mythcommflag did not fix the seek
> table correctly.  I haven't looked into why yet.
>
> Be well,
>
> Will         :-}
>


Since I actually want my machine to record shows, it will have to be some
weekend before I can debug this, and my weekends have been full.

Thanks for the info.  I will try this as soon as I can.


John