Having a glitch when exporting

[chris_3459]

Hi there,

I'm experiencing a weird issue when exporting a sequence.

I'm making a video of the year-end school performance of my daughter I shot last Christmas.

Everything is fine, except for the introduction sequence I'm making using a stock background video found on YouTube: it's basically a little shooting star moving across a red background.

For a nice effect, I'm using a black mate mask with opacity at 0 only around the little star and tracking it, with stereo effect of a glitter sound.

This happens three times before the mate mask reveals the whole imagine.

And it's precisely at the third occurence happening at around 00:00:08 to 00:00:09 that there's a glitch after exporting.

Weird thing is that there's no glitch for the two previous ones, and yet it's the same thing happening on the screen.

It's worth noting that the stock footage is 25 fps and my export is 60 fps, because I shot the whole school performance at 60 fps for smoother movements.

As for export settings, I'm using H264 codec with 2 pass variable bitrate set to 20 and 60 max, key frame pacing to 60 and time interpolation to optical flow.

All the export is nice, except for this glitch.

If someone has some time to take a look, here's a link to the project and the exported sequence showing the glitch: http://gofile.me/5CWqe/0ZHEiL99L

Thanks in advance!

[Joost van der Hoeven]

Hello @chris_3459 ,

This looks like a h.264 compression artifact to me. Try these two options:
1- Uncheck the Keyframe Distance option and let Pr choose it

2- What happens when you use the default preset: Match Source - Adaptive High Bitrate?

[Joost van der Hoeven · Accepted solution]

Thanks for providing the project and media. I see that the artifacts are already in the original stock animation. When the "comet" enters the screen from the top, it is already blurred and compressed. Fixing the Keyframe Distance to 60 or higher will force the compression to use the first "apprearance" and that one is not at good one. (see my screen grab, this is actually in the stock footage)
This is not a bug. In short: your source footage already has these artifacts and these are aplified with the export setting your are using.

[chris_3459]

Thanks for the advice, did an export and interestingly, the glitch is gone!

I'll try with the whole project, see if the bitrate values have a bad impact on the rest of the video.

[chris_3459]

Well, applying the default settings to the whole project seemed to work fine, the glitch has disappeared.

The only caveat is that the file size is 7,5 Go for 25 minutes of video...

I was hoping to keep it bellow 5 Go, so it could be burnt onto a DVD.

Any suggestions?

[Joost van der Hoeven]

Glad you found a sultion! yay!!
To lower the file size: Change the bitrate and keep an eye on the Estimated File Size (bottom right in the Export Window).

[Peru Bob]

You could burn to a double layer DVD.

[chris_3459]

That was indeed one option, but I'm trying to reduce costs as much as possible.

Thought two pass variable bitrate was better but it actually seems not.

I'll keep tweaking those settings and try to find the right balance.

Thanks for you advice and time!