Severe video playback issues

[lolmaus]

Hi!

When I'm browsing through a collection of short videos downloaded from then internet, I have issues with video playback.

Previously those were all animated GIFs, and everything was fine. But now they are video files, and the following issues happen:

1. For any video, there is a ~1 second delay before the image appears. When I switch to the next video, the audio playback starts instantly, but the image is black screen for a short while. If the video is a short looped animation, it won't be visible at all.
2. When browsing through videos, there's a chance that the video will not be visible at all and remain black screen. In order to work around this issue, I switch back to the previous video/image, then forward again. This means that the same video file will either fail or play randomly. It's not that some files always play and some always fail.
3. Some videos are very laggy. It feels like a low framerate, but it's not even. It's rather a 0.5 second freeze followed by 0.5 second of normal 30-FPS playback, followed by 0.5 second of freeze... The amount of lagging always varies, but unlike the previous problem, this is consistent across files: if a certain video file is laggy, it will always be laggy in XnViewMP.
   
   Here's codec info of one such video from an .mp4 container:
   
   Video: MPEG4 Video (H264) 640x360 29.97fps 685kbps [V: h264 high L3.0, yuv420p, 640x360, 685 kb/s]
   Audio: AAC 48000Hz stereo 128kbps [A: SoundHandler (aac lc, 48000 Hz, stereo, 128 kb/s)]
   
   This is a very typical container/codec used for millions of videos on the internet.
4. Screen tearing (lack of V-Sync). I have fast V-Sync enforced globally in GeForce Control Panel but this does not seem to help.
5. How do I make video playback loop?? I have found no video-related settings in Preferences.

Note that I have none of video playback issues in any other apps!

Please help.

XnView MP Windows Version 0.99.6 64bits (Dec 10 2021)
Libformat version 7.99
Windows 10 Pro 64-bit Version 10.0.19043 Build 19043
I have K-Lite Mega Code Pack installed but I have no idea if it's used by XnViewMP.
The PC is a very fast build: Ryzen 2700X, 64 GB RAM, Optane 900P SSD, 1070 Ti.

[Dreamer...]

confirm same bug

SJCAM SJ8
Video: HVC1 2704x1520 60fps 23758kbps [V: VideoHandler [eng] (hevc main L5.0, yuv420p, 2704x1520, 23758 kb/s)]
Audio: AAC 32000Hz stereo 128kbps [A: SoundHandler [eng] (aac lc, 32000 Hz, stereo, 128 kb/s)]

Mi Sphere 360
Video: MPEG4 Video (H264) 3840x1920 30fps 57286kbps [V: h264 high L5.1, yuv420p, 3840x1920, 57286 kb/s]
Audio: AAC 48000Hz stereo 127kbps [A: SoundHandler (aac lc, 48000 Hz, stereo, 127 kb/s)]

SJCAM SJ8
Video: HVC1 3840x2160 30fps 30505kbps [V: VideoHandler [eng] (hevc main L5.0, yuv420p, 3840x2160, 30505 kb/s)]
Audio: AAC 32000Hz stereo 128kbps [A: SoundHandler [eng] (aac lc, 32000 Hz, stereo, 128 kb/s)]

Samsung (smartphone)
Video: MPEG4 Video (H264) 2400x1080 29.97fps 19803kbps [V: VideoHandle [eng] (h264 high L5.0, yuv420p, 2400x1080, 19803 kb/s)]
Audio: AAC 48000Hz stereo 256kbps [A: SoundHandle [eng] (aac lc, 48000 Hz, stereo, 256 kb/s)]

Google Pixel 4a
Video: HVC1 3840x2160 30fps 43327kbps [V: VideoHandle [eng] (hevc main L5.1, yuv420p, 3840x2160, 43327 kb/s)]
Audio: AAC 48000Hz stereo 191kbps [A: SoundHandle [eng] (aac lc, 48000 Hz, stereo, 191 kb/s)]

XnView MP Windows Version 1.00 64bits
Windows 11 Pro 64-bit