ok, send screen

Why is your project interlaced (i)? It looks like your footage is progressive.

I'd change field order in project settings to none (progressive scan) and save it as a new preset.

Then when you render also make sure field order is none. You could also use MagixAVC which has a preset for Internet HD 1080p 25fps.

My GOPRO footage is progressive. The film that is to be rendered has a bullish 50i interlacing because a large part of the material is 50i, e.g. from the PMW200 camera. Until now, Vegas has been able to handle both 50p and 50i formats without a problem when I rendered the entire movie in 50i - interlaced. I easily put 50P clips from Panasonic GH5, HCX1, Sony A6500, AS200 in an interlaced project. The problem is with GOPRO.

I never work with interlaced footage so I don't know how to advise you.

One last thought is to change full resolution render quality from good to best.

ok, send screen

You're on "Preview (Half)", go to "Best (Full)", like this:

Your fps will drop drastically though...

I see you're using the Sony AVC codec. Can you try using the MAGIX AVC/AAC codec instead? That one is newer.

Also, it seems you are choosing a bitrate near the limit for the Sony AVC codec. Can you lower it to 21,000,000 b/s? The Magix AVC codec allows much, much higher bitrate and allows VBR And 2 pass in h.264. It also allows use of the NVENC chip in an Nvidia GPU to help render, as an option in each of the templates.

And another also, I'd suggest disabling hardware acceleration for your GPU in the options in Vegas. Many issues can be solved doing that. Try it once. Options > Preferences > Video tab > "gpu acceleration of video processing" - Off. Restart program. Undo if no change.

My GOPRO footage is progressive. The film that is to be rendered has a bullish 50i interlacing because a large part of the material is 50i, e.g. from the PMW200 camera. Until now, Vegas has been able to handle both 50p and 50i formats without a problem when I rendered the entire movie in 50i - interlaced. I easily put 50P clips from Panasonic GH5, HCX1, Sony A6500, AS200 in an interlaced project. The problem is with GOPRO.

When combining interlaced (1080i50) and progressive (2160p50) footage and Bluray is NOT the aim, I would go for 1080p50 output render with Voukoder. But first I would convert the interlaced (1080i50) footage to progressive (1080p50) with Handbrake and combine that footage with the Gopro 2160p50 footage in a Vegas 1080p50 project.

Hello, it didn't help. In the material recorded by Go Pro and bagged in Vegas, I have two problems all the time, loss of quality with a 4K 50p to HD downscale, and I cannot find 25i interlaced material. 4K 50p recorded with the Panasonic GH5 for example scales properly.

25i and 50i is the same thing.

Technically nobody calls 50i 25i but people do call 29.97i 60i.

I will tell you that it does not deliver Bluray to the client, but the HD 50i movie on a 20mb / s flash drive.

You will lose little quality when downscaling from 2160p50 to 1080p50, but you will lose a lot of quality when downscaling to 1080i50.

When there's no reason to export to 1080i50 (Bluray) than export to 1080p50.

Hello, it didn't help. In the material recorded by Go Pro and bagged in Vegas, I have two problems all the time, loss of quality with a 4K 50p to HD downscale, and I cannot find 25i interlaced material. 4K 50p recorded with the Panasonic GH5 for example scales properly.

This artifact may actually just be due to how modern LCD monitors display interlaced content. Also, many video players can TRY to "deinterlace" - which is impossible - so they have various methods.

My best suggestion is to try media player classic or try the file on your TV, which is designed to show interlaced content, to make sure it's just your monitor/program's problem.

Always better to convert interlaced to progressive in a mixed media project. Set the project settings to progressive then try again.