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Problem with HDMI external monitor videos


New Member
Surface Pro 3/ W10 Pro, AU

I've had a Samsung monitor as an external monitor (via HDMI cable) for a bit over a year now, moving videos over to the larger screen with no problems.

Today I noticed that when the HDMI cable is plugged in, most videos don't seem to want to play on either the Surface or external monitor. When I play a .wmv file, with the external monitor attached, the video slowly steps through each frame about once per second. When I detach the external monitor, the Surface plays the .wmv video normally.

YouTube videos won't play at all on either the Surface or the external monitor even if the external monitor is disconnected. [Playback ID: vHcbGmdfPrll9Nmk, for one error). Interesting (maybe) fact: When I move the cursor along the playback timeline/counter, the frames show up as if it were playing.

Flash-based videos on a different site no longer play even with the external monitor detached.

a .flv video played with the external monitor attached, on both Surface and external monitor, but with no sound; with the external monitor detached, the video played with sound normally.

.mp4 & .mov - with external monitor, sub-normal frame speed; normal with external monitor detached.

To me, it sounds like a HDMI cable issue... except why flash-based videos and YouTube won't play at all with the HDMI cable attached or not.

All this seems to have happened within the past couple of days.



New Member
Update: I restarted yet again... 3 or 4th time while 'playing' with this problem. Then something, I forget what, mentioned an audio problem. I went in and found my audio had defaulted to something called "C24F390". There are three files, one listed as my 'default communications device' with a green phone icon attached-- this was now the default device.

I switched to "Realtek High Definition Audio" and made it my default device... and all my video problems went away. Go figure.

My question now is: are those 3 C24F390 devices needed? For what? Where did they come from? How do I get rid of them? AND... why would an incorrect audio driver mess up my videos?