Tips for getting video to seamlessly loop?

[Dan Sloane]

Does anybody have any tips for getting QLab4 to loop videos seamlessly.   I'm creating loopable assets in After Effects that loop entirely fine within AE, these are then rendered to Prores 422 Proxy for playback in Qlab.   Every single video I've made so far has a very visible jump when it loops.

Playback is a Macbook Pro Retina, 2.5 GHz Intel Core i7 with NVIDIA GeForce GT 750M 2GB, 16GB RAM and 500GB SSD. 

Thanks,
Dan

[Abdel El Asri]

Hi Dan,

Sometimes for some reason, AE renders a black frame at the end. The loop can be obvious because of it. It may be that?

[Dan Sloane]

Thanks Abdel,

AE seems to render a black frame on the end of H264 videos, but doesn't have that problem with Prores. I've tried many files, including the unprocessed loop file from Shutterstock. 

After some experimentation, adding a slice as late in the cue as possible (possibly 1 frame?) then setting the first slice to infinite makes a much better loop, albeit with sacrificing one or two frames to make the loop seamless.  Either way it's more acceptable than just clicking the loop button.    I'm also seeing stuttering when a cue ends, so I'm wondering if if it's a disk read issue... my Macbook Pro has an SSD, but as it's running High Sierra it uses APFS so perhaps that's not yet tested thoroughly enough with QLab.

[Steven Sokulski]

There’s been some caution with High Sierra, same as with any other major OS release.

I don’t know if it is related, though.

Regarding the fact that trimming the last frame improves the loop, have you tru d simply ending the clip one frame early by changing the end time, rather than using a slice?

Something that occasionally happens with looping content is that the first and last frame are identical, which is not the desired behavior. For a seamless loop the last from should be one frame before the previous frame, six that replaying the first frame is the very next step in any animations.

[Chris Ashworth]

Looks like this is a QLab bug — we’re sending Dan a beta to try that should fix it, and if so I’ll post it to the Google Group as well.

(Thanks for the detailed description Dan; it triggered an idea that led right to finding the bug.)

Cheers,

C

[Abdel El Asri]

That's Awesome! 

[micpool]

The  bug's in all versions of 4.1

Loop playback seems perfect in 4.0.11. ( I don't think I've done a show with video loops since July)

Mic

[Dan Sloane]

Per my email to Sam, initial tests look good.   I'm going to run this evening's rehearsal using the beta and give you more feedback 

Thanks for the support and apologies for nagging over your Thanksgiving / our tech weekend! :)

 

Regards,

Dan

[Christopher Ashworth]

Correct; it has to do with the new feature to loop the whole cue rather than just slices in the cue.

When *just* the cue is looped the video engine was not correctly preparing a secondary buffer that it uses to ensure the loop is smooth.  (It was looking at just the slices and saying "no looping on this file; don't need to have a second buffer ready")

An equivalent bug for the audio engine got fixed this summer, but the video version of the bug slipped through until now.

C

(mobile)

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