skipping frames at the start of file

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nate
Posts: 22
Joined: Wed Oct 19, 2011 5:37 am

skipping frames at the start of file

Post by nate »

Hi eric/everyone,

I've been having trouble with frame numbers not lining up quite right and have discovered that comskip is skipping a few frames at the beginning of the file.

I've opened the mpg file with VirtualDub, and the original m2v file in Cuttermaran, and both show that the first 15 frames are:
IBBPBBPBBPBBIBB
however when running comskip with the output_timing option enabled the generated csv file shows the first 15 frames as
PBBPBBPBBIBBPBB
likewise if I enable output_demux and load the demuxed file in Cuttermaran it shows the same sequence as in the timing.csv

Looking at the content of the frames it seem the first 3 frames are not being output by comskip.

Do I have an option wrong in the ini file that is causing this? or is it a bug that will need to be addressed?

I've created a small sample file (30.8Mb) which can be used to replicate the problem. It can be download from
http://nate.dynalias.net/download/comskip/
The ShortSample.mpg file is what I am feeding into comskip.
comskip.ini is the ini file i'm currently using.
I've also made available the ShortSample.m2v and .mp2 files which were created by ProjectX and then fed into mplex.exe to create the mpg file.

I'm happy to provide any extra information, or assist with further debugging if required.

cheers,
nate
erik
Site Admin
Posts: 3368
Joined: Sun Aug 21, 2005 3:49 pm

Re: skipping frames at the start of file

Post by erik »

Did you test with the 0.81.012 version?
All new releases will be based on the codebase of the 0.81.012 version
Its currently available in early release area accessable by donators.
nate
Posts: 22
Joined: Wed Oct 19, 2011 5:37 am

Re: skipping frames at the start of file

Post by nate »

I currently only have 0.80.042. I'm assuming there have been changes since then that lead you to believe that this problem won't be present in the early access version?
erik
Site Admin
Posts: 3368
Joined: Sun Aug 21, 2005 3:49 pm

Re: skipping frames at the start of file

Post by erik »

At least the problem may be different :)
nate
Posts: 22
Joined: Wed Oct 19, 2011 5:37 am

Re: skipping frames at the start of file

Post by nate »

Hi erik,

I've now tested the ShortSample.mpg above with 0.82.016 and found that the frame types in .timing.csv match the input mpg, so that problem is solved, however there are problems with output_demux.

With output_demux enabled it is creating ShortSample.m2v, but ShortSample.mp2 is missing.
Also, when I load the generated m2v in Cuttermaran, as well as reporting temporal_reference errors and that "Not every GOP has a sequence header", the order of the frames show as BBBBPBBBBPIBBPBBPBBPBBI... so the first 10 frames of the file appear to be incorrect.

I hope that information is useful. Are there any other tests I can do to help out?

cheers,
Nate
erik
Site Admin
Posts: 3368
Joined: Sun Aug 21, 2005 3:49 pm

Re: skipping frames at the start of file

Post by erik »

When switching over to the new demux/codec many things broke as I wanted to have a test version available a.s.a.p.
Keep reporting them so I can fix them.

The demux output is the raw dump of the stream, possible when originating from a .ts recording. Video frames may start only after the first I frame.

Dont test subtitle data output. Its completely broken.

For the moment I prioritize stability and speed.
Then I guess that Live_TV will be important, but also difficult, to solve.
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