Stories and GOPs - Open or Closed

Question

Hi All,
I'm currently working on a DVD which is going to make use of stories to play different versions of the main feature (one version playing a concert with interceding documentary sequences and one where the docs are skipped). I have been trying to figure out if closed or open GOPs are best to use.
I've always used closed GOPs in the past under the impression that it gave a higher quality image but I've come across some posts on other forums saying that open GOPs give a better end result.
I also thought that closed GOPs gave better accuracy fro stories etc but this also seems to be not the case according to some posts I've seen.
Any advice people have is greatly appreciated.
John

Answer 1

Hi John
Open and closed GOPs refers to how your encoder encodes your MPEG stream. Closed GOPs will reference frames withing the GOP only. Open GOPS will go reference frames outside that GOP for a more efficient encode. Its been said that Open GOPs gives a better encode. You'll have to do some test to find out what you think. It all depends on the source material your using.
When you create a story, it just references the original cell number for the new title so whether you used Open or closed GOPs won't make a difference. It essentially a virtual title.