I-Frames interval for best quality XviD encodes

[simps]

This is for the eXperts on XviD thingy.
I read some ppl saying over the forums that P-Frames look better then I-Frames.

Is this true? If so, it is strange, because I-Frames r so much larger then P-Frames.

Anyway, i was looking for best quality encoding, and i tryed to use I-Frames interval of 1000 instead of default 300. Seeking the video with a 1000 I-Frame internal is ok for me, so thats not the problem. DVP642 can seek that good.

I used 1000 instead of 300, because ppl said that P-frames looks better then I-frames. So, i guess reducing the number of i-frame, would give me a better quality encode.

So is this true?

Because i made some tests, and its very hard to say if it helps or not, the quality is pretty much the same (visually) with 300 and 1000 interval.

But is this theory right?

Tkz ppl,
[]'
Simps

[junkmalle]

Using too high an interval makes it hard to seek within the file. I use 100. I also use QUantization mode so all frames are of equal quality.

[celtic_druid]

I frames are larger because the contain the entire image. P frames reference the previous I fame, which is why seeking can be a problem, especially when you take bframes into account.

Setting it to 1,000 doesn't mean that there won't be more frequent I frames than that, in fact I would think that most of the time XviD would insert I frames more often than that.

The recommended setting is 10*fps. So 250 if you are encoding PAL.

[simps]

Tkz for the replys guys.

Like i said, i dont have problems seeking encoded movies with large i-frame interval.

I know xvid will insert a i-frame everytime scene chances.
So when i set 1000 interval, in the end, i get an avarage real 500 interval for i-frames.

But my question really is, does this help in quality?
Because since i have fewer i-frames into my movie, i have more p-frames there. And ppl r saying p-frames are better looking frames.

So this is my problem, i want to know, is this theory of having more p-frames in the place of i-frames will help quality.

Also, if i-frames are larger then p-frames, if i use fewer i-frames, dont that mean that i will have more bitrate to encode the movie, and i will also have some p-frames on the place of i-frames (and ppl are telling me p-frames look better), so in theory at last, encoding with larger i-frame interval will give a better quality output?

Someone help me on this.

Tkz,
[]´
Simps

[junkmalle]

i made some tests, and its very hard to say if it helps or not, the quality is pretty much the same

Why don't you just trust your own eyes?

Let's assume, on average, an I frame is five times the size of a P frame. With the I frame interval set to 300, over 1000 frames you will have 3.3 I frames (assuming no I frames from scene changes) -- say the equivalent of about 1010 P frames. With the I frame interval set to 1000 you will have the equivalent of 1004 P frames. So the difference in size is less than 1 percent. Think you'll see any difference?

[simps]

junkmalle,

Tkz for the advice.

But i still want to know if having fewer i-frames will make a better looking output (of course, when comparing 2 same size encoded files), even if the difference is very small.

I hope some one can help me on this.
Tkz,
[]´
Simps

[junkmalle]

Simps, In case you didn't notice I added some stuff to my earlier post.