[mythtv-users] Commercial Flagging in 0.22 - no success.

[Manuel McLure]

On Fri, Feb 26, 2010 at 11:10 PM, Manuel McLure <manuel at mclure.org> wrote:
> Well, turning off comflagging while recording doesn't seem to have
> made a difference. I did notice that my SD recordings which are MPEG2
> seem to commflag just fine, while with the HD recordings (h.264) I end
> up with total garbage. I almost wonder if the detection is correct but
> for some reason the written offsets are wrong...
>
> I've switched from "All Methods" to "Blank Frame + Scene" and I'll see
> if any future recordings seem to flag better.

OK, I did an experiment. I took a half hour recording, skipped through
the flags, and wrote down the times for each skip. Then I went through
the program skipping by 30-second intervals looking for the commercial
breaks and wrote down the times for the start and end of each
commercial break. I ended up with the following extremely interesting
data:

Real Time      Skipped Time     Ratio
 7:18 (438)     5:37 (337)      1.3
11:19 (679)     8:53 (533)      1.27
16:51 (1011)   13:12 (792)      1.28
18:52 (1132)   14:47 (887)      1.28
24:18 (1458)   19:02 (1142)     1.28
26:20 (1580)   20:37 (1237)     1.28

Real Time is the actual location of the start or end of the commercial
break, skipped time is the place MythTV skipped to. The number in
parenthesis is the time in seconds, and the ratio is the real time in
seconds divided by the skipped time in seconds. Note that the saved
skips are off by a factor of about 1.3 to where they really should be
- it looks like it's correctly detecting the ads but somehow scaling
the frame number before writing it to the database. Maybe an artifact
of the h.264 encoding used?

I checked the recordedmarkup database entry for the last skip and it's
37081 which at 30fps is just about 20:37. The last entry in
recordedseek for the same recording is 53836 which is just about right
for a 30 minute show at 30fps.

Any mythcommflag experts want to chime in?
-- 
Manuel A. McLure WW1FA <manuel at mclure.org> <http://www.mclure.org>
...for in Ulthar, according to an ancient and significant law,
no man may kill a cat.                       -- H.P. Lovecraft