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frostfern

Major bug. Crossfade randomly missing after export.

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I am trying to create a video with a combination of photos and video clips.  I notice that when I export the video some of the crossfade transitions are replaced by the screen cutting to black.  It seems to occur randomly in different locations each time.  I gave up trying to render the entire video at once (since it takes over 2 hours) and instead decided to render each sequence separately.  I'm still having problems though.  The missing crossfades seem to occur in transitions between photographs and video clips.  This is extremely frustrating.  The crossfades appear correctly in the preview.  The problem appears exclusively after exporting to a video file.

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I am using version 5.11 on a Windows 10 PC.  I believe the error is occurring when using a crossfade at the end of a still image clip that is utilizing the zoom/pan effect.  Instead of crossfading the end of the still image clip as it should, the still image abruptly cuts to a black background as soon as the transition begins. 

I turned off the "use hardware-accelerated video effects" option in the tools->options->editing panel.  I'm waiting to see if this has any positive effect.  The random nature of the error makes me think it is somehow hardware related.

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If you can isolate a small segment of your project in which the issue occurs, please upload it.

One method would be to SPLIT out  that area and delete the rest, after using FILE|SAVE AS to back up the project.

Click FILE|SAVE AS PORTABLE PROJECT.  Upload to Dropbox, Google Drive, MS OneDrive or the like.  Make the link public and post it here.  Someone will check it out.

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The problem is the error is not easily reproduceable.  Sending you a single transition will likely not show the error.  If I have 15 transitions, the problem might occur randomly in one.  I can run the export multiple times and get a different result each time.  The error will occur on a different transition each time.  Also, the error doesn’t occur in the preview,  only the final output file.  Do you understand?

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Turning off hardware acceleration had no effect.  Can anyone explain why I would get a different outcome each time I export the file?    Does the program rely on graphics hardware for constructing the final file?  That seems like bad program design to me.  I would rather wait the extra time for the software algorithm to do its thing than have it rely on hardware and create a randomly botched output file.  God this drives me freaking nuts!  Does anyone know?

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Clearing the cache alone didn't fix the problem.  I fixed the problem by turning off "clear unused cache files when cache size exceeds..." option.  It seems like this option doesn't function like it's supposed to no matter how large I set the limit.  From now on I will just clear the cache manually before and after exporting the video.  This has worked so far.  Automatic cache clearing option is doing something funny during the render, even when actual cache data size used is nowhere near the max (I tested).  Might be a bug fyi.  Thanks for the help.

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If you zip that portion, and upload it with a public link here, as suggested above, others will look at it as well.

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Three Mp4 1920 x 1080 video file exports were run on your file...

1.  OPTIONS|CLEAR CACHE ON EXIT turned off

2.  Turned ON but with no exit

3.  Turned ON after exit

In each case the CLEAR...WHEN CACHE EXCEEDS 3000 box was checked.

All dissolves appeared in each test and no cuts to black were seen.

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I think it might need a longer segment.  My entire video is 18 minutes long.  Maybe try exporting several times without clearing the catch manually or on exit.  Also try playing the preview while it is exporting.  Maybe the cache has to get up around 1 gig.  I don’t have time right now to try myself.  Working.

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Update:

I've done some more research.  I haven't been able to trigger the transition cutting to black (TCB) error on the project I previously posted a link to on the board.  However, by experimenting some with different projects and watching the cache folder I've discovered some things.

Cache files are generated in three ways....

Process 1: Some cache files are generated automatically when the project is loaded.  These are video index files generated from the original video files included in the project.  They are generated while the "Laoding Project" dialog displays. 

Process 2: After the "Loading Project" dialog finishes, additional audio, video, and image cache files continue to be generated in a background thread.  This background thread may go on creating additional cache files for several minutes if the project is large, but the number of cache files will stop growing at some point if the program is left idle.  I assume the cache files generated by this background thread are used for generating previews.

Process 3: When a segment is being exported, additional cache files are generated.  I assume these additional cache files are needed for the final output because the final output is generated in a higher resolution than the preview.

Attempting to create an export file with TCB errors, I performed the following experiment on three different projects...

1.)  Uncheck "CLEAR UNUSED CACHE FILES WHEN CACHE SIZE EXCEEDS (MB)..." box, check "CLEAR ALL CACHE FILES ON EXIT" box.

2.)  In the Windows file explorer, go to .../Users/<user_name>/AppData/Local/Temp.  The file VideoPadCache appears here.

3.) Exit VideoPad  then re-open with the selected project.

4.) Let VideoPad sit idle and watch VideoPadCache in the file explorer.  Wait until the size of the folder stops growing (end of Process 2).  Keep refreshing and right-clicking on the folder to check the "PROPERTIES" dialog.  If the neither the number of files in the folder nor the folder size changes for a period of 2-3 minutes, Process 2 has ended.  Record the size of the cache.

5.) Go back to VideoPad, check "CLEAR UNUSED CACHE FILES WHEN CACHE SIZE EXCEEDS (MB)..." and set the limit to roughly half the cache size recorded at the end of Process 2.  For example, when the cache size was 2.2 GB, I set the limit to 1000 MB (1 GB).

6.) Exit VideoPad and re-open the project once more.

7.)  This time don't wait for Process 2 to finish.  Immediately export to video.

I notice there is some element of chance, but following the steps above increases the likelyhood of seeing TCB errors in the exported file.  In my case, TCB errors seem to occur exclusively after still images with a pan-and-zoom effect added.  I was also only able to get them to occur in projects with nested sequences (i.e. one main sequence consisting of two or more subsequences placed end-to-end).  They also seemed much more likely when the size of the project was large (2 GB or more) with many panning/zooming image clips.

While watching the VideoPadCache folder, I noticed that the total size of the folder always manages to exceed the limit set next to the "CLEAR UNUSED CACHE FILES WHEN CACHE SIZE EXCEEDS (MB)..." checkbox option, yet once it exceeds the limit it occasionally shrinks by a small amount before growing again.  From my observations, the threshold condition for deleting "unused cache files" is being triggered by the thread in Process 2, not the thread involved in Process 3.  Maybe the criteria for determining and communicating whether a cache file is still in use is faulty in some cases.

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