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Video Preview Uselessly Jerky (<2 frames/sec) on iMac Pro; smooth on PC

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I have submitted this problem to NCH Software over 40 days ago, and they have elevated it to their developers, but (despite my paid-for support), they have not yet been even been able to determine whether or not they can reproduce the problem. ([TK-wt7i400001-A12] Pty4 VideoPad TechnicalSupportRequest Mac)

Hence, I come again to this forum in hopes that some Einstein, Borate, or other kind soul can tell me what to do, and whether this problem occurs on all Macs, or just on mine.

In short, previewing a video clip on my iMac Pro, in either the sequence or the clip previewer, only occurs in very jerky manner, with a frame rate less than two frames per second. My iMac Pro has 18 processors, 64 GB RAM, Radeon Vega 64X GPU.  This jerkiness renders VideoPad useless for my basic task of synchronizing video of singers' mouths to their audio... you cannot see just when their lips change shape!

The capability is just fine on my HP Pavilion 27-a210, which has only 4 processors, 12 GB RAM, and an on-board GPU from Intel.  According to Geekbench 5 scores, my iMac Pro is 2.5 times more powerful than the PC on CPU tasks, and over 10 times more powerful than the PC on "Compute" tasks (which include a lot of graphics processing).  Yet its preview is much jerkier.

I surmised, and someone here confirmed, that the fact that the pixel density on the iMac Pro was 7.5 times greater than on my PC was contributing to the problem.

So I reduced my preview window such that its area was less than 1/7.5 of the area of the preview window on the PC, hence assuring no more pixels were involved in the Mac preview than in the PC preview.  I also cleared the cache as suggested.  Neither of these helped.  In fact, I intermittently got the problem that the iMac could not process .wav or .mp3 audio files... it would just sit "Processing." without conclusion.

Has anyone here had a problem with jerky previews on the Mac version of VideoPad (besides me?).

Anyone have any idea how to fix this?  So far it seems to have stumped the NCH software developers.

Is Videopad truly a product for the Mac as sold by NCH, or is it either unsuitable or needs something more?


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Thanks!  I have VP 8.79, which was the version linked to me about 3 weeks ago by NCH as part of their debugging, so I think it is the most recent.  The download file at the link you posted does not have a version number in its title... do you know what version it is?

The iMac Pro arrived three weeks ago new from Apple, so likely has most recent video drivers.  When I try to do a software update, it tells me its software (including video drivers, I presume) is up to date.

I don't have another Mac to try it on... I am just sticking my toe into the Mac world.  The hope is that NCH has a Mac to try it on, but so far no answer.

I do (and have always had) Hardware Accelerator turned on.



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Try turning acceleration OFF as well, if only just for kicks.  A new machine doesn't necessarily come with the latest drivers, but that likely isn't your issue.

The download page shows version 8.90 to be the latest for Mac.

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I downloaded the latest version, which indeed is 8.90.  By the way, how do you learn the version number without actually loading it and looking at "About?"

I tried turning off hardware acceleration... no difference - still less than 2 frames/sec.  Other diagnostics suggest that the preview processing does not use the GPU (where this machine is so much more powerful) that much... the graphic processing does get heavily used in the Export step. So maybe turning it off would not affect Preview that much anyway.

The iMac won't accept any driver updates... it reports that all its software is up to date. 

Still stymied!  Thanks for your help so far!

Does ANYONE here have experience with preview playback on a Mac?  Is it smooth or is it jerky?  Even that bit of info would help (as well as size of image, type of Mac, etc.)


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There's rumor of GPU usage improvements in the weeks ahead.  Whether that applies to Mac??  Logic hints that the issue is related to how VP interacts with the high-res monitor.  Is there a setting that allows the monitor to operate at lower resolutions?

This page has version info.  You can test a beta release if you're adventuresome.

While you say the current project runs fine on the old PC, it still might be instructional for others to check it out.  Upload and share it if possible, per these instructions...

1.  With your project on the timeline, click on MENU at the top-left.  Click FILE|BACK UP PROJECT FILES TO FOLDER.  Choose a folder and SELECT FOLDER.
2.  Locate the saved, numbered folder.  No need to upload the export or VPJ files.  Upload it to a free server - Google Drive, MS OneDrive, etc.*
3.  Get a shared, public link.  If using Google Drive click GET SHAREABLE LINK. Click the blue "Change to anyone with the link..."  Then click COPY LINK | DONE.
4.  Paste that link here, or click the folder, above top-right in this forum, and message it to me.  This is private and won't be shared.
*    Before uploading, right-click the folder, click PROPERTIES.  Look at the File Size to confirm that it's not too big for the free space on the server.


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Here is a link to a MS OneDrive with a folder 2020-10-12 17-38-2..Diagnostic:


There is one video file and one audio file.

If you run the video file as a clip on a MAC (iMac Pro, specifically), it is not too bad in jerkiness.

If you put it on the timeline and run it as a sequence on a MAC, it is jerky, at less than 2 frames per sec.

If you then put the audio file on the audio timeline, mute the audio from the video clip, and try to synchronize the audio file with the video (the audio file starts about 5:32 min:sec into the video), you will see how hard it is to synch, as the video jerks through several syllables at each frame.

It works fine on a Windows PC!

Anyone able to do this on a Mac?  Let me know... I cannot!


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No other Mac user has reported this, though they may be running lower-end machines.  Scaling down the monitor res, if possible, is worth a test.

On the PC here, playback was seamless - no jerkiness whatsoever.  It appears that not all singer tiles are in sync.

If the mp3 recording was not sync-locked to video, its speed may not match up - even if recorded at the same time.

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What a great suggestion... to scale down the iMac Pro monitor resolution.  It helps tremendously.

A little experiment... turns out the jerkiness of the image is matched by a jerkiness in the cursor timer, which displays only about 2 sub-second values within each second demarcation of the counter (on the PC, the sub-seconds advance smoothly, as the frames play smoothly).

Here is what I found:

PC:  1920 x 1024  smooth - continuous subsecond advancement on counter and smooth motion in image

MAC:  Default - 2560 x 1440 - jerky, 2 subsecond advancements per sec on counter and two frames per sec

MAC:  Reduced Res: 1280 x 720, 1/2 as wide window - about 1/8 the number of pixels as Default - almost smooth, jerkiness too little and frames too many per second to count

MAC:  Closest pixel count to PC - 2048 x 1152 - more jerky than Reduced Res above but not as much as Default - usable.

Thanks, borate, for all of your help.

The example you presented (done with a PC) is exactly what I get (with a PC) - the singer tiles are NOT all in synch, because it is from a Zoom meeting with separate electrical paths for each image - however, in the final product, I can and do fix that (but need the non-jerky resolution to do so!)

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Though putting the resolution of the iMac Pro on its lowest setting still has some jerkiness, there remains an unusable level of jerkiness on feedback to real time actions such as cropping... as you move the mouse to define the crop boundaries, they sit still for a while, then respond to your mouse actions all at once, overshooting what you want.

Likewise, other actions such as minimizing a track height, starting or stopping play, and the like all have a delay to them.

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  • borate changed the title to Video Preview Uselessly Jerky (<2 frames/sec) on iMac Pro; smooth on PC

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