NVOPs in Xvid - good? bad? nonrelevant?

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Hi everybody.

I recently noticed (via GSpot) that some of my Xvid files contain NVOPs and others don't. I encoded all of my files using the same Xvid settings in AviDemux2.

I read up on NVOPs and found out that they can appear when using B-frames (which I did). Now I'm wondering what the existence of NVOPs depends on. Is it the source material?

Also, do NVOPs have any influence on the video-quality or the compatibility with DivX-certified DVD-players? Are NVOPs good, bad or nonrelevant?

Any advice is much appreciated.


~ Regards.

[jagabo]

N-VOPs appear when you use b-frames and packed bitstream. They are simply placeholders for the kludge that allows VFW to read out-of-order frames. As long as your player supports packed bitstream (most now support it but some older players didn't) you don't need to worry about them.

Packed bitstream and N-VOPs: https://forum.videohelp.com/topic373432.html#2007975

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I've been using AviDemux2 with the settings suggested in this thread: https://forum.videohelp.com/topic347091.html#1820201 . So I didn't activate the checkbox for "packed bitstream" on the main-tab.

GSpot doesn't say anything about packed bitstream either, which it should if there was one... (or am i wrong here?). Still the "NVOP"- and "DF"-fields are highlighted.

Any clue what's happening here?

[jagabo]

Yes, GSpot indicates if packed bitstream is used. The little PB next to the other VOP flags.

There are two types of N-VOPs, zero duration and non-zero duration. The former are used with Packed Bitstream. The latter (DF) are used when an frame is exactly the same as the last one -- indicating the same frame should just be displayed again. This most often happens with totally black frames. You can use VSS the tools in GSpot to examine the VOP sequences.

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I'll have a look into VSS - thanks for the info.

Do you know whether non-zero duration N-VOPs can cause playblack problems with DVD players? Or is the compatibilty the same as with zero duration N-VOPs?