"choppy" playback on pans [Archive]

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Enrico Ng

20th May 2004, 00:07

I notice that many times, pans look like they are at a lot frame rate. even when I cap a 480p stream at 60fps.
For those I choose even to make it 30

But if there is a pan, it looks rather choppy.

I found one thread about this in the xvid forum, but it suggested I not use B frames. My usual settings are all all default, no bframes, no chroma and Turbo.

I notice that sometimes with HDTV streams, in DVD2AVI2, it will say like 75% NTSC 25%FILM. Is this significant? I read about like if its 5% NTSC and 95% FILM, I should Force FILM, but I don't know about this. could this be related?

oh not, my FOX 480p streams are resized to 852x480 and my 1080i captures are resized to 768x432 using LancozeResize in avisynth

polyvinyl

25th May 2004, 00:28

I believe that I may be having a similar problem, except that I am not encoding my video with xvid.

I have encoded a 720p HDTV transport stream in WM9 using avisynth and virtualdubmod. The output avi looks perfect except that the video gets choppy/jerky in some action scenes where everything on the screen is in motion (eg: camera pans). I usually play videos using media player classic, but I noticed that when I play the final avi using windows media player 9, there is no jerkiness and the video plays completly smoothly. Does anyone know what could be causing this problem or how to resolve it.

The avisynth script that I loaded into virtualdubmod is:

LoadPlugin("C:\AviSynth 2.5\plugins\UnDot.dll")
mpegsource("source.d2v")
UnDot()

(the source.d2v file is the saved project file from DVD2AVI2)
I am also putting the AC3 audio from the transport stream into my avi.

I have tried reducing the quality and complexity of the WM9 encoder settings and have found that the jerkiness remains even if I have the quality set very low!

Also, I have a 3.0 Ghz cpu, and I know that my computer can handle HDTV WM9 video because I have played samples from microsoft's website successfully.

Zep

28th May 2004, 06:42

Originally posted by polyvinyl
I believe that I may be having a similar problem, except that I am not encoding my video with xvid.

I have encoded a 720p HDTV transport stream
The avisynth script that I loaded into virtualdubmod is:

LoadPlugin("C:\AviSynth 2.5\plugins\UnDot.dll")
mpegsource("source.d2v")
UnDot()

you are doing a full 59.94 FPS?

do a selecteven()

then check for dupes if you have them then decimate(5)
odds are will solve your problems.

high motion will always be a little jumpy at 24 FPS
but it should be ok as long as it is an even steady frame
rate with no dupes that make the high motion stuff stutter
when a dupe frame is seen. In low motion they are harder
to notice.

Enrico Ng

28th May 2004, 07:35

polyvinyl

28th May 2004, 10:29

Originally posted by Zep
you are doing a full 59.94 FPS?

do a selecteven()

then check for dupes if you have them then decimate(5)
odds are will solve your problems.

high motion will always be a little jumpy at 24 FPS
but it should be ok as long as it is an even steady frame
rate with no dupes that make the high motion stuff stutter
when a dupe frame is seen. In low motion they are harder
to notice.

I have tried this method to reduce the framerate and it makes the output file less jumpy, but the jumps are still there. Also, I still don't understand why the file plays fine in windows media player and not in media player classic. Also, I have seen other people's encodes of similar source material who keep the full 59.94 framerate and have no choppyiess whatsoever even when played in media player classic.
I understand that reducing the framerate will help alleviate my problem, but because the jerkiness remains and because other people have successfully made such encodings, I can't help but think that the problem is being caused by something else.

If I used another denoiser that made the video a little smoother, could this possibly make it easier on the video codec and thus make it easier to decode and help my stuttering problems?

Zep

29th May 2004, 22:34

Originally posted by Enrico Ng
my source is 720x480p 59.94

I do this with avisynth:
MPEG2Source("E:\video.d2v")
SelectEven()
Crop(96,0,-84,0)
LanczosResize(640, 480)

ok but my reply was to polyvinyl :D

As for yours

yours is really just pdtv so more that likely 29.97 Hybrid

"it will say like 75% NTSC 25%FILM. Is this significant? "

Yup mixed source is a pain. Because if you leave it at 29.97
then the film parts have dupes and the video parts are good.
If you decimate then the film parts are good but the Video then
is CHOPPY every time it hits that missing frame.

read the dvdtoavi faqs.

it explains how to do hybrid so that the FPS is 29.97 but you get rid of the
film dupes and replace them with tweened/interpolated frames instead.

i say read the faq cause all i would do is re invent the wheel and also that
is where i learn to do this anyway so.... :D

Zep

29th May 2004, 22:49

Originally posted by polyvinyl
I have tried this method to reduce the framerate and it makes the output file less jumpy, but the jumps are still there. Also, I still don't understand why the file plays fine in windows media player and not in media player classic. Also, I have seen other people's encodes of similar source material who keep the full 59.94 framerate and have no choppyiess whatsoever even when played in media player classic.
I understand that reducing the framerate will help alleviate my problem, but because the jerkiness remains and because other people have successfully made such encodings, I can't help but think that the problem is being caused by something else.

If I used another denoiser that made the video a little smoother, could this possibly make it easier on the video codec and thus make it easier to decode and help my stuttering problems?

well at 59.94 the dupes are going by so fast it looks ok. (note this is on FILM
source but it would look AWESOME if they decimated(5) to 48 FPS)

if video there are no dupes, so 59.94 will be SUPER SMOOTH as it
truly is 59.94. All the pdtv video i get is truly 59.94 with NO DUPES.

IMHO that is OVERKILL and 29.97 is plenty.
High speed pans are always gonna be a little jumpy at 29.97 or under.
(note not stuttering. I mean jumpy as in the distance between
objects moving from one point on screen to the next is huge without
those extra frames)

As for WPM VS classic. Make sure classic is using the same decoder.
I bet it is not.

polyvinyl

30th May 2004, 11:32

Thank you Zep! You were right, I slowly stepped through the frames in virtualdub and there were duplicates. After re-encoding with the decimate and selecteven in my avisynth script, the stuttering problems went away.
What is strange is that I checked the other 56.94 fps encodings that I was talking about earlier that were similar and didn't have any stuttering and found that they also had duplicate frames in them yet somehow they didn't have the problems that I had.

Zep

30th May 2004, 16:16

Originally posted by polyvinyl
Thank you Zep! You were right, I slowly stepped through the frames in virtualdub and there were duplicates. After re-encoding with the decimate and selecteven in my avisynth script, the stuttering problems went away.
What is strange is that I checked the other 56.94 fps encodings that I was talking about earlier that were similar and didn't have any stuttering and found that they also had duplicate frames in them yet somehow they didn't have the problems that I had.

well it depends on the source and how the dupes are laid out.

for HDTV film you may have

1 2 3 4 D 1 2 3 4 D

so the dup frames are not evenly spaced and it looks bad

on other source (video) it may be

1 D 1 D 1 D

so even though you have LOTS more dupes
they ARE evenly spaced so you will never notice them.