[mythtv] Bug? HD-3000 DVB driver timestamps

[John Patrick Poet]

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.

At first I assumed that some change had been made to the commercial 
flagging code, but then I noticed that a show which should have a length 
of 1h 1m, was indicating that it was 1h 5m long.  The commercial 
flagging was consistantly off in the same way -- the begin marker was 
always a bit before the actual commercial, and the end marker was always 
a a bit before the show started up again.  The amount of time between 
the detected commercial marker, and where it should have been, grows as 
the position in the show increases.

There were no blank frames anywhere around where the commercial flagger 
indicated the markers should be.

I decided the problem had to be with the DVB HD-3000 driver, so I 
switched back to the V4L HD-3000 driver on Sunday, 17 Apr 05.  Since 
then my show lengths have been acurate, and the comercial flagging has 
gone back to being near perfect.

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?

Thanks,

John