[Kdenlive-devel] "jerking" video - last twist in story?

[Jan Uhlir]

I tested my troubled example video clip towards possible interlaced/progressive/TFF/BFF mishandling.
Here is the detailed description and the results of my 6 experiments.

I rendered the example video clip in Kdenlive in two ways.
Common attributes: - Video 4 Mbps (0min, 8 Mbps max), Audio ac3 192 kbps, gop_size=12 me_range=63 b_frames=2 real_time=0
1 - rendered_20070608_interlaced.vob - progressive=0, (result: 317 frames, 12.5 MB file)
2 - rendered_20070608_progressive.vob – progressive=1 (result: 317 frames, 10.4 MB file)
Original had 7.5 MB and 332 frames.

Frame order:
Excellent! b_frames=2 work as described, now the frame order is IBBPBBPBBP.. as is in original.

Both clips were reencoded in Avidemux, both in two ways to test the interlacing options.
"Avidemuxing" using AVG bitrate, all codecs and bitrates same as in Kdenlive, video 0-4-8 Mbps, audio: ac3, 192kbps:
3 – avidemuxed_20070608_1.vob – interlaced (1) to interlaced TFF, (result: 314frames, 5.7 MB file)
4 – avidemuxed_20070608_2.vob – interlaced (1) to interlaced BFF, (result: 314frames, 5.7 MB file)
5 – avidemuxed_20070608_3.vob – progressive (2) to progressive, (result: 314 frames, 6.0 MB)
6 – avidemuxed_20070608_4.vob – progressive (2) to interlaced TFF, (result: 314 frames, 6.0 MB)

** Test results, PC (xine, kaffeine, mplayer)
As usual all movies fully playable, no visible defects observed.

** Test results, HW DVD player + TV:
1 – Usual jittering, only half of the movie playable, it stops in the middle. Worse result then expected.
2 – surprise! seems to be OK. BUT only half of the movie playable, it stops in the middle.
This is the first video directly playable from Kdenlive on hardware DVD player + TV without usual jittering!
3 – OK, small hardly noticable jerks (missing frames? lower framerate?)
4 – Jittering pisture! This is the firs video from Avidemux I produced which jitters when played on hardware DVD player + TV!
5 – OK, just one jerk on the very beginning, best variant
6 – OK, small but noticable jerks (missing frames? lower framerate?)


** Conclusion

Tests proved that my picture jittering problem was caused by mishandling interlaced video during Kdenlive rendering. It treats TFF interlaced videos wrongly as BFF?

The workaround for now is to force Kdenlive/MTL renderer convert video (treat video as) to progressive by using flag progressive=1 in profile parameters.

As Dan suggested, DV videos are BFF, mpeg2 could be both TFF (as in my example clip) or BFF. BFF interlaced or progressive videos were rendered OK, so most users didn't experienced any problems with jittering like me. To make it more scarce, the defect is apparent only when played on hardware DVD player + TV.

Audio codec selection or a/v bitrate or frame order proved to have NO effect on the jittering issue.

For the frame decreasing number issue I opened a separate thread.

The "only half movie playable" issue - have to get more data & do more experiments. i will let you know. It's hard because it happens only when played on HW DVD player on TV.

Next time I would try the latest SVN version with modified rendering. See you Sunday!


___________________________________
> Od: dan at dennedy.org
> Komu: kdenlive-devel at lists.sourceforge.net
> CC: "Jan Uhlir" <espinosa_cz at centrum.cz>
> Datum: 07.06.2007 07:03
> Předmět: Re: [Kdenlive-devel] "jerking" video - last twist in story?
>
>On Wednesday 06 June 2007 19:32, Jan Uhlir wrote:
>> I am able to produce hardware compatible DVD now. No jerks or
jittering.
>> However it requires full video reencoding of BOTH audio and video.
>> I tested many variants of a/v bitrate and many other settings but only
one
>> setting is relevant. Guess what. Interlacing! The video is OK only when
I
>> set TFF as interlacing option. (TFF - top filed first I guess) When I
set
>> "progressive" jerkiness is back! The very same issue.
>> So the story is back where it began - at interlacing :)
>
>I saw from a link to a picture in your original post that it is
interlaced.
>What did you use to record the source material? DV is always BFF, but
MPEG-2
>can be either and must be signalled properly. Since kdenlive/mlt/ffmpeg
is
>doing progressive encoding, it would have been signalled as progressive.
>However, with interlacing in the source and no good deinterlacer, you
will
>get this result.
>
>> P.S.
>> I haven't test BFF option yet.
>
>Please do and report to us.
>BTW, what format are you using between kdenlive and avidemux?