[Kdenlive-devel] IPB frame order and possible link to my "jerking" video?

[Jan Uhlir]

Avidemux exported sequence, non-jerking video:

Frames sequnce
I(06) B(08) B(08) P(06) B(08) B(08) P(06) B(08) B(07) P(06) B(08) B(07) I(06)

I frame i every 12 frame, so GOP = 12 ?
B frames present, interesting.

Image size		720x 576
Frame Rate		25.000 fps
# of frames		332 frames
Codec 4CC		MPEG
Video duration		00:00:13.280
Aspect Ratio		Pal 4:3 (16:15)

Extra properties:
Packed Bitstream	No
Quartel Pixel		No
GMC			No

Audio:
Codec			AC3
Channels		STEREO
Bitrate			32000 Bps / 256  kbps
Frequency		48000 Hz
Audio duration		00:00:13.472
VBR			No


Kdenlive rendered, jerking video, the same clip:
I(31) P(18) P(12) P(08) P(06) P(06) P(06) P(06) P(06) P(06) P(04) P(04) P(06) P(06) P(06) I (06)
I frame i every 15 frame, so GOP = 15 (as was set in render profile)
There are no B frames at all!

Image size		720x 576
Frame Rate		25.000 fps
# of frames		320 frames (12 frames missing, interesting!)
Codec 4CC		MPEG
Video duration		00:00:12.800
Aspect Ratio		Pal 4:3 (16:15)

Extra properties:
Packed Bitstream	No
Quartel Pixel		No
GMC			No

Audio:
Codec			AC3 (MP2 also tested)
Channels		STEREO
Bitrate			56000 Bps / 448  kbps (128, 192, 256 kbps also tested)
Frequency		48000 Hz
Audio duration		00:00:12.768
VBR			No

forum.doom9.org: GOP's: I, P, and B frames explained...
http://forum.doom9.org/archive/index.php/t-19436.html 

This information is interesting:

I noticed some confusion about B frames, so I thought I would write down a quick explaination of an MPEG "GOP", or, "Group Of Pictures", as explained to me by a professor
...
Oh, BTW, in MPEG2 at least, a GOP order is always IPBBPBBPBBIPBBPBB etc etc. (pending on your GOP size), but it is always 1 I, 1 P, and 2 B's, then you can stack more groups of "PBB"'s in that one GOP if needed (usually up to 15 total frames.
...

This information indicates that Avidemux processed clip (cut and copy operation from original stream) is very close to this IBBPBBPBBPBBI.. order. And this works!

Contrary, Kdenlive exported video is IPPPPPPPPIPPPP.. only stuff. No B frames at all. May this be related?  Is this MTL or Kdenlive specific? What avlib parameters I can use to achive desired IBP frames combination?

Any possible link?

Thanks for any help
Jan