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Duplicated frames in latest version


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I am using the latest version of Videopad professional (v3.81), on a Windows 32 bit machine running Windows 7.

 

The two faults have been present in previous versions too, and are easily replicated.

 

Take any two clips, with movement so that each frame transition can be easily seen, and place them on the timeline (could also accomplish this by placing a single clip on the timeline and splitting it).

 

If this simple sequence if exported, everything is fine.

 

Now, firstly, if a simple fade transition is used between the two clips, everything appears fine on the sequence pane when stepping through frame by frame. However, when exported (mp4, H264), duplicated frames exist at the start, mid-point, and end of the transition. Frames are also missing, so that the exported sequence is the same length as the original sequence. These duplicated/missing frames can be easily seen by adding the exported video file to the project, and stepping through, frame by frame, and comparing to the original sequence.

 

Secondly, if we return to the original dual clip sequence, without a transition, and add a visual effect (e.g. brightness) to the second clip as an effect across the whole clip, without using keyframes, then the exported file is fine. However, if we use keyframes to vary the brightness across the clip, then the exported file has several duplicated/missing frames across the whole clip (seem to occur every fourth frame).

 

Both of these faults cause visible stuttering in the exported file, which renders these effects/transitions unusable.

 

These problems have existed in the software for several months, across several updates/releases. I cannot use the software in its present form, which is a pity, as other than these significant faults, the software is nice to use.

 

Please advise.

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Hi

 

Do you think this might be related to the length of the transition and the framerate that VP uses?

I think you may be seeing a "still" frame for this reason... VP goes frame to frame at 25 fps. If your transition does not accomodate a whole number of frames you will see (sometimes) what seems to be a duplicate frame.

 

e.g. Place your two clips on the time line and add a fade of 3 seconds between the clips. As you say correctly the fade-in fade-out plays OK. and if you step through the transition there doesn't appear to be a still frame. But it seems to depend on where you start stepping frame by frame from.

 

If you zoom in using the slider and place the red cursor line exactly at the start of the yellow 3 second transition bar and step left a couple of frames and then step frame by frame to the right may see that the first frame after the start of the transition shows no movement. Which is, I think what you are seeing and interpreting as an extra still frame.

 

What I think is happening here is that with a 3 second transition the start of the effect is 1.5 seconds before the join. At 25 fps it means 37.5 frames before the end of the first clip.....which can't be done if you start stepping exactly at the beginning of the transition... VP therefores shows no new frame at the start as it would be missing out a frame or jumping the half or to the middle of a frame so the frame is shown again until the step catches up. If the clip is played normally though the frames are complete each time and a still frame is not seen.

It's just an idea as I suppose the software simply divides things up mathematically and then rounds up or down the values.

 

If you change the transition to a 2 second fade there will be exactly 25 frames from the start of the transition to the join at the midpoint and you won't, therefore see a still "duplicated" frame.

 

It may be the same for the keyframe settings, if the points chosen don't match a whole number of frames at 25 fps.

Also, something similar might happen if your output fps is set at 29.97. Is it any better if you output at 25 fps?

I am only guessing BTW. :mellow:

 

Nat

 

P

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Hi jrse63,

 

I did some testing and found the frame time diverged(from the original clip) as you said.

 

Nat's probably right, it could be some kind of numerical rounding errors.

 

We'll further investigate the issue and get it fixed.

 

Thanks.

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Hi, I originally thought that the time positions of the transition or key frames may have caused the problem. However, this is not the case. I am using a source and exported file frame rate set to 25 fps. My transition length was set to exactly 0.4 seconds, yielding 0.2s before and after the transition. This is exactly 5 frames before and after. I was also careful to set the transition point at an exact frame end/start point (I.e multiple of 0.04s from the start of the clip). The key frames were also set at exact frame endpoints.

 

It is therefore not a rounding error. If a randomly chosen transition point or length is used, then the frame duplication/deletion still occurs, but at different points. Please note that the error is in the exported file, not in the sequence preview.

 

Also note that frame duplication can occur without transitions or key frames if clips are not joined at exact frame end/start points. I do not understand why VP does not only permit clip in and out points to be set at frame end/start points, rather than at any time down to 1ms resolution.

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Hi jres63,

 

We can see the time divergent more clearly with overlapping the exported sequence on top of the original sequence, and then make the top layer track 50% transparent. The frames are shifted during the entire transition duration.

 

We are working on the issue and will get it fixed.

 

Thanks for the information.

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