Nero Vision DVD slide-shows, invalid??

[lrms]

Using Nero Vision a friend of mine create an slide-show from JPEG pictures. We noticed some players (like some LG standalones) would not respected the time when playing the stream (would also have other quirks).

Playing the VOB directly in PowerDVD and WinDVD also reproduced the problem of timing not being respected. But playing from the DVD menu would work fine.

Analyzing the m2v stream extracted from the VOB, I noticed it is made all of I-frames, one for each picture. Also each frame is chapter (one frame per chapter).

The work-around we found was adding a soundtrack (of silence in this case), which solved the bug for PowerDVD at least (still to be tested in LG standalone players).

Now here is my technical question:
With ~4s per picture, is this slide-show created by Nero a valid mpeg2-video stream (standard-DVD wise)? I thought I've read somewhere that standard DVDs should have an I-frame every 1s (at most)... (0.4-0.6s typically).

[mpucoder]

The last frame of a sequence, even if the sequence is only one I-picture, can be extended in time, but only in the DVD context. A VOB file is an mpeg-2 program stream, but with DVD specific extensions. When played as a DVD, which means with the ifo file, the slideshow should work properly, even though the information to extend the last frame is in the vob file. But when played as an mpeg file, ie the vob file alone, the DVD extensions such as NAV packs (where the timing for slideshows resides) is not processed.