Infoseite // GOP in a lot of movement

Frage von PeterBrand:


Hi!

First, in general:
Can anyone recommend me a really good article relating to GOP? In principle, it is clear what are the I, P, B-pictures, but somehow I do not yet "the button" succeeds, what does their arrangement.
Beautiful would be an article that brings some practical examples of how it should proceed with more quieter and faster as more sequences.

And with respect to Premiere Pro: what are the M-and N-Frames?

Now a specific question:
Had a sequence in a film that is very quickly cut and has a lot of movement. The rest of the film is kept rather quiet. And these pictures with a lot of movement begin tw. to jerk.
As an AVI it works naturally. M2v depending on the setting times with or without stuttering, but this is really strange, tw. rucktelt the VOB file after authoring with DVD-Lab (synonymous if the underlying m2v file works perfectly).

If this sequence to be encoded separately (with different GOP structure than the rest)?
Probably right, I suppose. -> And then?
- Together with the individual MPGs as TMPGenc again a?
- Or the individual MPGs consist only in the DVD authoring program?

Danke schon mal
Peter



Antwort von Markus:

"Peter" wrote: Can anyone recommend me a really good article relating to GOP? In principle, it is clear what are the I, P, B-pictures, but somehow I do not yet "the button" succeeds, what does their arrangement.
Hello Peter,

I do not have a link, so I describe it times fast. Let's start with a typical GOP structure, how do I find it often on DVD-Video (MPEG2):

... IBB PBB PBB PBB PBB IBB ...

At the beginning of the GOP (Group Of Pictures) is a full frame (I-frame) is stored. After that will be registered for the following 11 frames, only the changes, with a B-frame changes to the previous I-, B-or P-frame described, while a P-frame saves the changes to the previous I-frame. This mix will be a read or minimize transmission errors, the impact on the current video image.

"Peter" wrote: ... a few practical examples which, just like when you tend to proceed as in the quieter and more rapid sequence.
The GOP structure is usually during a video the same. To display detailed images with a lot of movement as well as clean, quiet sequences can vary the data rate or as defined in the beginning of a higher value.

"Peter" wrote: ... Pictures with a lot of movement begin tw. to jerk.
Video can be a jerk synonymous if the data rate is set too high. In this case, many DVD players become temporarily stalled. Compress the video with times "d 8 Mbit / s. What causes yet to come for a juddering video image in question, you pack everything: DVD Burning

"Peter" wrote: If this sequence to be encoded separately (with different GOP structure than the rest)?
No (see above).



Antwort von Pete:

Hi!

Wait until now to reply to it.

Thanks for the info.

At the data rate is not my problem. I've already tested. And the "judder" occurs already s.PC on the hard drive.

In the scene, a woman is dragged into a lake into the water -> namely a lot of movement of the performers, "flying" hands and hair, the water hochschappt, Camera tw. under water, etc., etc. So REALLY MUCH motion ;-)

In TMPGenc, the problem does not occur. Rendered directly from Adobe Premiere Pro MPG out as I have basically improved dzt. a (light) picture quality, but the jerking occurs depending on the setting of the N-and M-frames sometimes more difficult to manchal.

Ultimately, I'll probably have to experiment a bit until I found out the end result Richigen ;-)

Thanks
Peter



Antwort von Markus:

Hello Peter,

The encoder, in addition to the above-mentioned aspects have a significant impact on the MPEG2 result. This is often to try out the air - or the purchase of a correctly good encoder. TMPGEnc is certainly not bad, especially for the price. Even the Procoder Express (little brother of the much more expensive Procoder) is readily called in this context.



Antwort von Axel:

Try it once, the critical points, encode with a constant data rate. Sounds horribly wrong, but do not always make the best encoder out quickly changing image content. Every second frame has a completely different image content, such as synonymous with short cuts, is the variable encoding with "high-motion estimation," in my experience, more appropriate than, for example a recording of a carousel. There is continuity of frame to frame and motion blur. Variable Mean target data rate for high-motion estimation since led to unnatural effects, could be called jerky. With a constant data rate of all was in order.