Fixing GOP sizes for DVD compliance. Good or bad?

[Supremus]

When recording DVB content, sometimes the GOPs are too long to be DVD compliant. I use Womble MPEG VCR's GOP Fixer tool to correct it, but I was wondering if this might be a bad idea? I don't fully understand the nature of GOPs and whether they can be re-arranged/fixed without causing any problems. When I playback the files, I don't notice any difference, but since it's usually only 1 or 2 GOPs, it might be in areas where I don't notice it? Does anybody have any thoughts or concrete info on this?

[BJ_M]

should not create a problem

[Supremus]

Cool.

I just had an idea for a "controlled" experiment. I might just try and encode a short test clip with lots of motion and long GOPs. I will then fix it, and see if I can spot any differences.

[Ducky]

Hello,
Tried to have an answer from Womble message board, but didn't have any luck...
Does the Womble GOP fixer tool actually encodes the video? Im wondering since the output files are bigger than my source files...
Plus I've noticed that the picture gets just a little lighty and then normal, then lighty (particularty noticable on white tv logos - but it's barely noticable) after the GOP being fixed.
Any ideas?

Etienne

[Ducky]

^ any help appreciated

[Supremus]

As I understand it, long GOPs will reduce the filesize slightly, so by re-fittimg them to DVD specs, it would make sense that the files got a little bit bigger. I have not noticed any difference in quality on the clips I tested, and considering how quickly a file is processed, it seems unlikely that any real re-encoding is taking place.

Other than that sort of speculation, I don't have any solid information on the subject.

[Ducky]

ok, thnak you. as im not sure either, ill try to find out and let you know