Colorful dots instead of video, Resolve 16, RX 580

Good morning/afternoon/evening everyone,

Having a weird issue with Resolve 16.0.0B.017. The task's pretty simple IMHO: I've got a recording of a stream and a recording of the complementary chat window which I have to add (blend) above the stream recording, to the upper left corner. Specs are as follows:
* Ryzen 1700 stock
* 2x16G DDR4 2400Mhz stock
* RX 580 8G stock, Adrenalin 19.1.1
* 7.2K HDD & SSD, using the HDD for this for a peace of mind (no previous experience & understanding of possible export file sizes in Resolve. 3 hour long 1080p60 vid.) Yet I don't think it should be an issue.

The issue is that I only see colorful dots in the thumbnails. To add salt to the injury, sound plays but the screen is perfectly blank (black) in both media and edit panes. (That is, Resolve has trouble playing the files.) Whether it means anything or not for Resolve, I've got K-Lite Mega pack of codecs set up on the machine so I should be stuffed with those. The files play absolutely fine with no stutter in Media Player Classic. Project settings are 1080p60 and default for everything else.
For the record, I tried the same video idea before on another machine (4700MQ + GT 740M "Fermi" variant) and it played without issue in Resolve, not even stuttering. Problem was, the render time kept climbing. I cut it out at around 5 hours (the estimate was higher at that point) and decided to try again on this build. Would be relieving to know what render time I should expect from this one.
Stream recording is 60fps H264 yuv420p "main L4.2" (according to MPC-HC) with 128k AAC audio.
Chat recording is 30fps H264 yuv420p "high L3.2" with 2k AAC (muted). The program duly suggested I let it change the timeline settings to 30fps, while I could also leave it as-is. Neither option helped.

Here's what it looks like in the program window.

glitch1.jpg (305.97 KiB) Viewed 537 times

Including this to prove and verify that the files are A-OK.

glitch2.jpg (273.19 KiB) Viewed 537 times

Any suggestion will be most appreciated.

[Peter Chamberlain]

It sounds like the codec u selected isn’t supported. Resolve doesn’t use codec packs so the Kpack isn’t relevant.
You need to also record audio at the same rate as your video.

Before trying anything else, start a new project and add a Blackmagic raw clip form our web site to test the system.
Samples here
https://www.blackmagicdesign.com/produc ... ckmagicraw

Also, in preferences, system, make sure the first drive listed is the permanently connected high speed drive for stills cache and waveform

Sorry for the late reply, and thank you so much.
The test encode was impeccable. I blended clip 2 over clip 1 and added transitions. The playback in Resolve was just a tiniest bit choppy but the output was perfect (Shotcut with its effect glitches -- they refuse to render sometimes -- says hi ). And it got encoded in realtime, 20 seconds in 20 secs out - I think that is moreless in line with the average for this spec. And 25MB in size, that's preeetty compact.
Tried rendering that initial project yesterday. It took 1 hour (3 hour video) and put out a perfectly green screen, but the audio was good Maybe I'll have to reencode first, after all. Yet again, it was fine on a 4700MQ+740M system before (just crawling slow).
Best regards