x264 keyframe pumping

[turbojet]

Hi,

I'm having some trouble getting decent results encoding some hybrid clips, here's a sample of the source (http://www.mediafire.com/download.php?eatk3yioyyf). I've found out it's because the keyframes look so much different then the P/B frames.

What I need is:
- crf 26-30, they are BD extras
- max-keyint 24, need very quick seeking due to menu calling them in different spots
- vbv maxrate 25000 vbv-buffer 25000 or lower for DVD playback
- interlaced since they are hybrid clips

Things that I've tried that do help but they don't meet the requirements:
- crf <20
- max-keyint >120 or so
- xvid has no pumping at bitrates around what crf 26-30 give and max-keyint 24 although it doesn't look very good.

Does anyone have any suggestions on reducing the keyframe pumping?

[Dark Shikari]

I can't replicate any sort of "pumping" effect on that clip: the P-frames and B-frames are nearly 100% skips, so I can't imagine how one could possibly claim them to be "different" from the I-frames.

Now, what you might be referring to is the fact that the I-frames look slightly different from the previous P-frame, due to intra prediction giving different results than inter prediction. There are only two ways to avoid this kind of popping (other than the obvious of using a very high bitrate or not putting I-frames on non-scenecuts):

1. Use periodic intra refresh and no I-frames. Not possible on a DVD.
2. Use an encoder that encodes each I-frame as a P-frame, and then encodes the I-frame relative to the P-frame instead. Can result in progressively degrading quailty throughout a long near-static scene.

I could hardly notice the effect visually while watching (I had to actively look for it), so I don't really think it's a big problem in this case.

[turbojet]

I forgot to mention that sample is the source, if you encode with --crf 26+ --max-keyint 24 I think you will notice it.

I've done some other hybrid clips the same way and they've turned out fine but they didn't have telecine info on the borders.

[Dark Shikari]

I forgot to mention that sample is the source, if you encode with --crf 26+ --max-keyint 24 I think you will notice it.Yes, I know, that's what I did.

"Pumping" in my mind refers to the case where keyframes are significantly better quality than the frames around them--something that is not the case here. This is just intra prediction differing between keyframes, something you'll notice even more if you set the keyframe interval to 1--which means P and B-frames have nothing to do with it.

[turbojet]

Here's a sample (http://www.mediafire.com/download.php?y4zmzqjzroq) which may emphasize the issue a lot more.

A few other things I found out that help the issue a bit are:
- cropping the borders then readding them, this is a possibility for my situation
- not using --interlaced which isn't a possibility in my situation but in this sample no interlaced produced a smaller file with less of the issue. The full clip was considerably smaller with --interlaced with the same settings, does this make sense?

Also on this sample xvid does produce a little bit of the issue with interlaced enabled, without interlaced it doesn't have the issue. HCenc and CCE both don't show the issue. DivX 7 emphasizes the issue a bit. Do you know if this issue is some interlaced MPEG4 or even H.264 deficiency?