[Bug]: Periodic framerate hiccups (Noticeable in 240p Test Suite scrolling test, affects games)

[vanfanel]

Dolphin version

Github version fd1aca3

RetroArch version

Latest stable (1.22.2)

Platform

Linux

Renderer

Vulkan

Game exhibiting the issue

240p Test Suite for easy reproduction, but can be seen in all games

Describe the issue

An easy way to see this is to use the 240p Test Suite, run the Scroll Test and pay attention to the scrolling movement: after a while sporadic hiccups can be seen

• This happens no matter what options are set on the core (Precision Frame Timing, Skip Duplicate Frame) or RetroArch, periodic hiccups can be observer.
• This happens using both Vulkan and OpenGL(GL/GLCore) renderers.
• I use Debian 13 GNU/Linux with a lightweight Wayland compositor (Labwc), latest stable MESA3D on AMDGPU, and ALSA sound.
• No other core does this: 240p Test Suite is used to verify correct frame pacing and should display no hiccups on the scrolling test, so this seems to be specific to this core (for example, Flycast passes the test with no hiccups).

My guess here is that this core, contrary to other cores, is not controlled by RetroArch's buffer swaps, but does it on it's own somehow and sends the frames periodically to RetroArch: from my knowledge about how RetroArch works, all cores (providing a sane configuration is set) should be controlled by RetroArch, thus making them hiccup-free.

Log Output

No log is relevant I guess. This is a visual/synchronization/framerate problem.

[cscd98]

Could you try the test with async audio enabled? (precision frame timing, accurate CPU cache etc should be off)

Remember to restart the core when changing async audio setting

[vanfanel]

I tried, but that makes no difference: periodic hiccups still happen.

[SuperFranky84]

This problem has always been there with this core, even before @cscd98 started with its updates.
I notice it especially in the cutscenes of Zelda: Twilight Princess

[cscd98]

It's definitely something I will look at if nobody gets the chance to do so first, I've got a back log of TODOs.

[McRmie]

I noticed this issue not too long ago also with the 240p test suite and I was able to completely fix it on my end.

Note that the "hiccups" -at least on my PC, even when they were occurring, happened once every 5-6 seconds or so and only for a single frame, so some people might probably not even be able to notice it.

I used this scrolling test:

A bit of info:

First off, I'm on Windows, did not test on Linux. Also, I'm still using the last version of the older core before the recent update/sync of the core - the newer core does not appear to work on Windows 8. This is most likely due to the standalone Dolphin officially dropping support for Win 8 with version 5.0-16393 (3 and a half years ago) So the up to date core probably inherited this as well as the older core was based I think on an even older version than that.

Anyway, the fix might still work for the newer core so might be worth testing.

Curiously, at least for me, the frame hiccups seem to have been caused/fixed by some audio settings. Here are the settings that somehow fixed it for me:

audio_driver = "xaudio"
audio_latency = "52"
audio_out_rate = "32000"
video_driver = "vulkan"
video_max_swapchain_images = "2"
video_shader_enable = "true"
audio_rate_control = "true"
audio_rate_control_delta = "0.005000"

"audio rate control" and "audio_rate_control_delta" seems to be the determining factor. Each test I did with audio rate control disabled I had frame hiccups, when I enable it, no hiccup/stuttering.

edit: I should add I don't normally have audio_rate_control enabled and I don't experience frame hiccups with other cores with it disabled (using the 240p test suite for other systems as a benchmark) so this solution might not be a "clean" fix -more like a workaround and like vanfanel said it might be ultimately caused by something specific to Dolphin/the dolphin core and how it handle frames maybe.