Playback briefly pauses when waveform cursor reaches next subtitle

[hisui3393]

Description:
During playback, there is a brief hesitation or micro-stutter
when the waveform cursor reaches the start of the next subtitle.

Environment:

• OS: Windows 11
• Subtitle Edit: 5.0.0-beta21
• Video: (mkv H.265)
• Audio: ( mp3)

Steps to reproduce:

1. Open a video with subtitles
2. Start playback
3. Observe the waveform cursor while approaching the next subtitle line

Expected behavior:

• Playback should continue smoothly without interruption

Actual behavior:

• Playback briefly hesitates or stutters
  exactly when the waveform cursor reaches the next subtitle start time

Notes:

• The issue seems synchronized with subtitle timing, not random
• It may be related to waveform rendering or subtitle focus updates
• The hesitation is very short but noticeable during continuous playback

Frequency:

• Happens consistently when moving across subtitle boundaries
  The issue was slightly noticeable in Subtitle Edit 4.
  but it is significantly more pronounced in version 5.

Impact:

• Affects smooth playback and timing work during subtitle editing

Question:
Is this a known issue related to waveform rendering or subtitle event handling?

[hisui3393]

Additional observation:

The stutter is most noticeable after editing subtitle text.

Steps:

1. Edit the text of a subtitle line
2. Start playback immediately
3. When playback reaches the next subtitle line,
   a brief hesitation occurs

Notes:

• The issue is significantly more noticeable right after text editing
• It seems related to UI updates or subtitle state changes after editing

[GrampaWildWilly]

This sounded intriguing so I tried it. Understand that I'm just a fellow user here, not a dev. My environment is Windows 11 Pro 64-bit version 25H2 build 26200.8328 & SE 5 beta 21. I think perhaps my hardware may be relevant as well. CPU is 13th gen Intel Core i9-13900K with 128G of RAM. Video is NVidia GeForce RTX 4070. I'm using the MPV player in SE, but I've symlinked it to a more recent version than what Nik is distributing at the moment, 0.41 vs the 0.39 he's currently distributing. Plus I am running with the video controls undocked. The main SE window & the Audio visualizer are on my primary monitor & the video player is on my second monitor, which is my TV. I'm not seeing any of these micro-hesitations you're reporting, not even after making some changes to subtitles. This sort of thing can often be a result of hardware that isn't powerful enough. It can also be a result of other things running at the same time in background. I regularly see a momentary black screen during video playback. When I rewind & play the passage again, the black screen does not recur. This is in SE as well as just plain old video playback not in SE. This is just Windows, like it or not. Also, Nik has recommended for as long as I can remember that you use the MPV player. If you're not, switch to that & see if your problem goes away. Otherwise, I have no advice. Like I said, I'm just an ordinary user.

[hisui3393]

Thank you for your suggestion, GrampaWildWilly.

I updated mpv.conf to reduce GPU load, and the hesitation is now much less noticeable.

In my case, it seems that performance limitations were a contributing factor.

Thanks again for pointing me in the right direction.

My graphics card is a GTX 960, which is an ancient GPU, so that might have affected its performance.

[hisui3393]

Additional findings:

After adjusting mpv.conf to reduce GPU load and improve buffering behavior,
the playback hesitation became significantly less noticeable.

Changes included:

• enabling cache
• reducing scaling quality
• disabling high-precision seek (hr-seek=no)

The issue is still slightly present,
but much less disruptive during editing and playback.

This suggests that performance and buffering behavior
play a significant role in this issue,
especially on older GPUs (GTX 960 in my case).