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Videos I watch play back at massively increased speed when my Mac is connected to this particular external monitor.

Series played on HBO Max, for example, progress at about a 30x rate, meaning I see mostly individual frames and buffering animations (which, oddly, play at normal speed) -- it looks like videos are basically stuck in fast-forward.

Video playback is sped up across multiple browsers (Chrome, Safari), and playback of local files appears to be affected as well (the first I play a local file, it just skips to the end immediately, the second time seems fine). The issue with the playback speed of streaming video is reproducible on two entirely separate Macbooks when I connect them to this monitor, an LG 29KW600.

Unplugging the external monitor, which is connected via HDMI through a USB-C hub, instantly resolves the issue. Videos then play back at normal speed on the laptop's screen.

I've tried killing coreaudiod in an attempt to resolve this issue, without success.

Any insights as to what might cause this external monitor to affect video playback speed would be much appreciated. Thanks in advance!

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11
  • This sounds like an issue with the HDCP function of the monitor. The fact that you can reproduce it on two different MacBooks points further in this direction. Try it with a PC Laptop to see if it still exists. You will want to contact the manufacturer to see if there is a resolution.
    – Allan
    Commented Apr 18, 2023 at 23:43
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    I have a similar problem with an M1 Mac and a DELL-U3219Q. It only happens when I use the Dell monitor as an audio destination, and as well as playing super fast the sound gets distorted. Doesn't happen with my work M2 Mac Pro.
    – frabcus
    Commented May 28, 2023 at 11:15
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    A complete reboot fixed the problem for me. So it looks like this is yet another audio bug in macOS on ARM. I've had constant bugs caused by the way they made the headphones and internal speakers look like two sources, weird bugs where every app that uses CoreAudio locks up hard, etc. CoreAudio is just an absolute disaster on M1. I'm not hopeful that macOS 14 will fix anything, given that macOS 13 didn't.
    – dgatwood
    Commented Jul 21, 2023 at 2:13
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    I have this problem now for the first time. Only with sound on the external monitors. M2 Max. Killing coreaudiod did not help.
    – mindhaq
    Commented Sep 6, 2023 at 9:18
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    Same problem since months, I feel that it happens when RAM usage is high but I don't have data to back this.
    – Fabien Sa
    Commented Jan 29 at 16:13

5 Answers 5

Reset to default
6

In appreciation of Alaa's response, I can confirm on fully updated system which was showing the same issues all of a sudden (not had it in a year), the fix for me was as Alaa suggested. I’d like to summarize it rather than editing that post in case it helps others:

  • I went into audio settings and set it back to using the in-built speakers and not sending audio out the DisplayPort, and it worked.
  • No reboot required.

Now just got to work out why this is the case. My suspicion is routing the audio across the connection to the display is triggering some bug or undesired protocol transition. Keeping the audio off the display is the key to resolving this at the moment.

Both my issues have been using different Macs but all with LG monitors. 🤷🏻‍♂️

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3
  • I have the same issue and changing the settings also works for me
    – Jordan Réjaud
    Commented Feb 23 at 12:55
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    IMO your answer is better (more complete and informational) than Alaa's
    – Chris Davies
    Commented Apr 25 at 8:42
  • Well done, anyone can edit, but sometimes making a new post is most helpful especially on ones so briefly stated.
    – bmike ♦
    Commented May 4 at 14:08
1

I had this same problem and just completely restarting my Mac seemed to work. The monitor I used was an LG 35WN75CP-B.

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1

I rebooted my computer and the audio through external monitor is now working. I'm using macos 14.5 with a thunderbolt connection to the monitor.

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0

after reading the comments and answers I decided to restart my Mac and it fixed the problem. For context I have a M1 MacBook Pro and it's hooked up to a 4k Samsung monitor without built in speakers through a cheap Chinese USBc hub, although the HDMI is 2.1. And my monitor speakers are connected to my monitor through the AUX port. Hope it helps!

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-1

use your device speaker to fix

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