Workaround for inaccurate commercial skipping in Sage!

[Tundra-]

I've long since had an issue where commercial breaks don't seem to line up properly in Sagetv with the timestamps generated by Comskip or Showanalyzer...resulting in commercial skipping that is often significantly too far ahead or too far behind the end of the commercial break. (I don't use autoskip, but I suppose it would hose that also).

I've seen that some other people have noticed this as well. In some cases, people have indicated that switching from txt to edl or updating Tssplitter.ax or increasing the frequency of NTP clock syncs has helped. My situation seems to have nothing to do with any of that...and for the longest time I just ignored the issue assuming it was due to some rounding error or keyframe issue or clock sync issue or some other such mysterious thing.

Eventually, it annoyed me enough to take a much closer look -- after all, it seems silly to me that even with so much computing power and technology I can't even rely on being within a few seconds of a frame-precise comskip'd or Showanalyzer'd file.

In my case (other's cases may be quite different), I noticed that alternate media players would report a media file duration which was usually quite different than the scheduled sagetv recording time (note this has nothing to do with padding). For example, just about every recorded file I have shows up about 5 seconds shorter or longer than the sage media player shows on its timebar. 4-5 seconds isn't perfect, but is probably not a big deal. However, some shows are much worse than 5 seconds. Some extremely long files, such as 3-5 hour Tour de France stages , are off by up to 30 seconds or more by the end. This has an extremely negative impact on the accuracy of the commercial skipping within Sagetv -- even though the actual comskip/sa edls are perfectly accurate. The issue worsens as the show progresses as the Sagetv timeline diverges more and more from the 'real' timeline of the media file.

Evidently, my recordings are not being done at precisely 29.97 fps. I cannot say exactly what it is that makes the recording run long or short; however, after some pondering, it seemed apparent to me that if I were to go back and fudge the edl numbers to correspond to this ratio of 'scheduled duration' vs 'actual duration' it might be able to correct the issue.

Basically, I created a script which takes a file argument and calls a process to gather the media file's actual duration information and creation/last_modification timestamp information. (I'm currently using open source project MediaInfo (command line version at http://mediainfo.sourceforge.net to gather the duration info). It then parses that info and uses it to rewrite the edl with adjusted timestamps.

From my tests so far, it seems to solve my problem completely. I now have literally split-second accurate commercial skipping within sagetv! Since I kick off all of my comskipping with independent batch files and such, it is an easy matter for me to integrate this script into my normal comskip processing. It only takes a few seconds to run the skipfix after comskip/sa finishes analyzing the file.

It is of note that adjusting the edl timestamps could potentially break something else...perhaps media extenders or placeshifters could then have accuracy issues...or there may be issues specific to HD setups or nonMpeg2 files...I have no idea. But for my setup (windows, non-hd, pvr250s, server and client), it works great.

So, if you've experienced inaccurate skipping, take a look at your media files in an alternate player. If the duration differs from the sagetv player duration by even a few seconds, then you likely suffer from the same issue.
If someone else has an easier solution to this issue, let me know!
Otherwise, if people besides me are still having this problem, let me know and I'll clean up my code and post it.
Hopefully, with these and further insights, we'll find ways to squash this issue once and for all!


Tundra-

[EmuZombie]

I'd definately love to see this posted.

I'm having the same trouble. Durations differ by a few seconds, but like you said, after a few hours that ads up

[kevine]

I'd like to see it too. Thanks.

[Tundra-]

Here you go...short and sweet. I tried to clean it up a bit and add some comments.
Check the comments at the top of the script for info.

Tundra-

[boonest]

I love the idea, but can't get it to work. I get a VB error. Should I have a certain version of VB runtime installed? I'm using WinXP Pro. Also I am using Sagemc with comskip and would like to know if there is a way to have skipfix automatically run when comskip is done.

Thank you for your time and effort