I tested this on a newer laptop with a USB-C port and a built-in card reader. I have used both the microSD slot on this reader and the SD slot with a microSD card in the adapter. In both cases, the video file on the microSD card (U3) was slow to read, with the video pausing intermittently before continuing. I used the built in card reader on the PC and there was no slowdown in video playback, so the problem wasn't with the SD card or the adapter. Interestingly, video playback from a USB stick plugged into the reader was flawless. I also found the USB-C connector to be very snug in and out of the PC. Hopefully it will loosen up after long time use. So the reader worked well, but not great.
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