I just received my new Raspberry Pi 4 w/4 GB RAM. The NOOBS SD card had a pre-release version of Buster, so I downloaded the released version ("2019-07-10-raspbian-buster-full.zip") and installed it on a high-performance Sandisk microSD card (128GB "Extreme Plus" A2).
I booted up Buster on the RPi 4, plugged in a Seagate 4TB Backup Plus drive containing videos, and discovered that Buster doesn't support NTFS drives out-of-the box. So, after a diversion to install ntfs-3g (don't remember having to do this with Stretch), I selected a random MPEG-4 video using the File Manager on the desktop and double-clicked. It came up as expected in VLC.
My surprise was the playback performance -- it was very jerky. (I took all the defaults for VLC as it was run by clicking on the file name.)
I was suspicious that Buster might not be as optimally configured as Stretch, so I shut down the RPi 4, removed the microSD card with Buster, and inserted it into my RPi 3 Model B+ (2017), and booted it up. Exactly the same peripheral hardware -- Seagate HD, keyboard, mouse, and screen. Picked the same action movie. Played the same scene. Not jerky -- played perfectly. Tried two more movies at random -- same jerky behavior on the 4, but played perfectly on the 3.
The only difference was the RPi 3 in place of the RPi 4. The RPi 4 should have out-performed the RPi 3 by a wide margin, but did not.
Has anyone else seen this behavior with their new RPi 4s? I ran all the updates on Buster, but I didn't update the RPi 4 firmware -- should I have done that? (I can't test it on OSMC as they have not yet announced support for the RPi 4.)
Tech info: The Codec info tab on VLC shows exactly the same information for the RPi 3 and RPi 4 --
Codec: H264-MPEG-4 AVC (part 10) (avc1)
Video Resolution: 1920x800
Frame rate: 24464.900096