On Mon, 18 Apr 2005 23:16:30 -0600, John Patrick Poet <[EMAIL PROTECTED]> 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         :-}

--
Dr William Uther                           National ICT Australia
Phone: +61 2 9385 6357               Computer Science and Engineering
Email: [EMAIL PROTECTED]          University of New South Wales
Web: http://www.cse.unsw.edu.au/~willu/     Sydney, Australia

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