Old 05-14-2024, 07:06 AM   #1
DThompson55
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Default Green Glitches in Rendered Video

I've been using Reaper to edit and render our church services. Someone pointed out that these videos are littered with green video glitches like the ones shown here:

https://www.youtube.com/watch?v=A2wKiSgGfmE&t=1802s

My render settings are:
MPEG-4/Windows Media
MPEG-4 1920x1080 30fps
H.264 2048 kbps
ACC 128

Resample Sinc Interpolation 192pt

I had never thought to go back and look after they were rendered. I just assumed they were good to go, and then posted them to YouTube. They are not in the original media items, only in the rendered files. Any thoughts as to what might be causing these problems?

I guess I'm going to spend an afternoon this week and try different render settings, then report back. All of these videos are nearly an hour in length, so it's going to take a while. I'm relatively sure this is not a Reaper problem, but more likely a problem with the render settings and whatever engine is doing the actual compression.
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Last edited by DThompson55; 05-15-2024 at 06:15 AM. Reason: more information
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Old 05-15-2024, 10:34 AM   #2
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Could be many things but it looks like a buffer underrun somewhere. Either the video source decoder itself has trouble keeping up (ex: overheating laptop reducing its clock speed) and/or there is disk read problem (ex: dying disk or a network disk). I would also try rendering with "online render" option (or other ones) just to see if it helps

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Old 05-15-2024, 12:01 PM   #3
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I'm a complete newbie when it comes to video, but I've only seen green screens when "show underruns during playback as green frames" is selected under the video windows Options->Performance tweaks (experimental). Maybe check if that's selected? It doesn't really make sense that unselecting it would help since you're rendering, not playing back, but maybe as an experimental feature the green frame insertion got leaked into the render process, I dunno.
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Old 05-15-2024, 03:06 PM   #4
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I might have stumbled onto something. The original video as 29.97fps. I was rendering at 30fps. I just went back and tried rendering at 29.97. I haven't watched the full hour yet, but spot checking seems to show it's OK. I'll report back next week.
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Old 05-20-2024, 07:54 PM   #5
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I'm still having a problem. Matching the render FPS to match the input item's FPS made no difference.

More detail - I import an approximately hour long video into a single track. It's the only thing in the project. The only FX on the track is a Volume/Pan V5 and ReaLimit, with no FX on the master. I render with normalize/limit on to bring the loudness down to -14LUFS if it goes over that.

Render seems to go normally, but the rendered output file starts to have video freezes and green glitches after about 30 minutes. The audio is fine. Only the video is affected.

I don't see anything in video preferences that might affect this. Buffer underruns and the suggestions that were given for increasing buffer size seem to be related to recording, not rendering? Maybe I'm missing something?
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Old 05-21-2024, 05:27 AM   #6
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Quote:
Originally Posted by DThompson55 View Post
<snip>
Render seems to go normally, but the rendered output file starts to have video freezes and green glitches after about 30 minutes. The audio is fine. Only the video is affected. <snip>
Definitely looks like the computer is overheating. What type of computer are you using? A laptop? I would try rendering with the "1x offline render (idle)" option to reduce the stress on the machine.
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Old 05-22-2024, 06:01 AM   #7
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The machine is a purpose-built video/streaming machine. Windows, 16GB RAM. I'll keep an eye on the performance monitor.

Some videos have the issue. Others do not. We're trying to narrow down what's different on projects that have the glitches and those that don't.

It would be sad to have to change to a 1x offline render time. But if that's the only fix... well, we'll just have to wait and see.
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Old 05-22-2024, 10:25 AM   #8
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Quote:
Originally Posted by DThompson55 View Post
The machine is a purpose-built video/streaming machine. Windows, 16GB RAM. I'll keep an eye on the performance monitor.
<snip>
Oh! wrong hypothesis unless one of the heat probe is faulty. I would investigate on the storage unit on which the video source is stored. Could be bad sectors on conventional HDD or an overheating or worn out SSD.
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Old 05-27-2024, 06:29 AM   #9
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OK I think I have a work around. I just copied the video file from the Windows box to a Mac and used Reaper there to render. The video comes out small, which is good. Almost as small as using the native Windows-MPEG drivers. AND there are no glitches. So I'll just do that for now. Added bonus, the hour long video renders in about 8 minutes on the mac.

I'm the only one in the congregation with Reaper on a Mac, which means nobody else will be able to do these edits. But on the other hand, I'm the only one who's done them for the last 8 months.

I ran diagnostics on the Windows box, memory and hard drive, and they looked good. But the performance monitor pegs at 100% memory usage. It's far lower on the Mac. Maybe that had something to do with it.

Also, while I was working on the Windows box I set the render to 1x real-time, and it did not produce those glitches. But, I did not want to sit around for over an hour just to render.
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Old 05-27-2024, 12:04 PM   #10
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Quote:
Originally Posted by DThompson55 View Post
<snip>
I ran diagnostics on the Windows box, memory and hard drive, and they looked good. But the performance monitor pegs at 100% memory usage. It's far lower on the Mac. Maybe that had something to do with it.
<snip>
Really 100% *memory* usage? Some process in the computer has gone wild or leaks memory. This causes virtual memory page swapping and this is definitely a cause for this type of problem. Even if it were 100% CPU that would be the same.
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