No thumbnail for MKV videos, only preview works

[janosorcsik]

Thumbnails aren't showing for MKV videos in Finder, though the preview works fine in QuickLook.
My default media player is Movist Pro, and the QuickLook extensions are already enabled.

Can you help me fix this?

---

QLVideo: 3.03
macOS: Version 26.3 (Build 25D125)
Hardware: Mac14,9, Apple M2 Pro, neon=yes
Previewer: Not found
Thumbnailer: Not found
Media Formats: 3.03
Media Codecs: 3.03
Spotlight: Imported 'file.mkv' of type 'org.matroska.mkv' with plugIn /Applications/QuickLook Video.app/Contents/Library/Spotlight/QLVideo Metadata.mdimporter. 40 attributes returned

{
  "programs": [
  ],
  "stream_groups": [
  ],
  "streams": [
    {
      "codec_name": "h264",
      "profile": "High",
      "codec_type": "video",
      "codec_tag_string": "[0][0][0][0]",
      "width": 1920,
      "height": 804,
      "display_aspect_ratio": "160:67",
      "pix_fmt": "yuv420p",
      "extradata_size": 42,
      "disposition": {
        "default": 1,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    },
    {
      "codec_name": "dts",
      "profile": "DTS-HD MA",
      "codec_type": "audio",
      "codec_tag_string": "[0][0][0][0]",
      "sample_fmt": "s16p",
      "channel_layout": "5.1(side)",
      "disposition": {
        "default": 1,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    },
    {
      "codec_name": "hdmv_pgs_subtitle",
      "codec_type": "subtitle",
      "codec_tag_string": "[0][0][0][0]",
      "disposition": {
        "default": 0,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    },
    {
      "codec_name": "hdmv_pgs_subtitle",
      "codec_type": "subtitle",
      "codec_tag_string": "[0][0][0][0]",
      "disposition": {
        "default": 0,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    },
    {
      "codec_name": "hdmv_pgs_subtitle",
      "codec_type": "subtitle",
      "codec_tag_string": "[0][0][0][0]",
      "disposition": {
        "default": 0,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    },
    {
      "codec_name": "hdmv_pgs_subtitle",
      "codec_type": "subtitle",
      "codec_tag_string": "[0][0][0][0]",
      "disposition": {
        "default": 0,
        "attached_pic": 0,
        "timed_thumbnails": 0
      }
    }
  ],
  "chapters": [
    {
      "start_time": "0.000000",
      "end_time": "510.218000"
    },
    {
      "start_time": "510.218000",
      "end_time": "1046.545000"
    },
    {
      "start_time": "1046.545000",
      "end_time": "1532.823000"
    },
    {
      "start_time": "1532.823000",
      "end_time": "2045.085000"
    },
    {
      "start_time": "2045.085000",
      "end_time": "2693.608000"
    },
    {
      "start_time": "2693.608000",
      "end_time": "3327.908000"
    },
    {
      "start_time": "3327.908000",
      "end_time": "3743.949000"
    },
    {
      "start_time": "3743.949000",
      "end_time": "4360.314000"
    },
    {
      "start_time": "4360.314000",
      "end_time": "4850.429000"
    },
    {
      "start_time": "4850.429000",
      "end_time": "5421.833000"
    },
    {
      "start_time": "5421.833000",
      "end_time": "5769.764000"
    },
    {
      "start_time": "5769.764000",
      "end_time": "6333.285000"
    },
    {
      "start_time": "6333.285000",
      "end_time": "7564.432000"
    },
    {
      "start_time": "7564.432000",
      "end_time": "7828.320000"
    },
    {
      "start_time": "7828.320000",
      "end_time": "8152.811000"
    },
    {
      "start_time": "8152.811000",
      "end_time": "8920.128000"
    }
  ],
  "format": {
    "format_name": "matroska,webm",
    "duration": "8920.128000",
    "size": "22454628688",
    "bit_rate": "20138391",
    "probe_score": 100
  }
}

[Marginal]

You've tried the "Refresh" button?

[AuroraWright]

Can confirm this on macOS 15.7.4. What I tried:

• untoggling/retoggling both the two Media Extensions and the Spotlight checkbox in system settings/login items (they're in separate menus on macOS 15 apparently)
• clicking the refresh button
• completely uninstalling QLVideo with Pearcleaner and rebooting, and copying it back again

I see all the video metadata on right click and most mkvs have a working video preview on spacebar, but no icons. Icons show up normally as soon as I restore 2.23.

I also tried checking on mdimport -L and the mdimporter is correctly listed. Also tried doing mdimport -o output.txt -t filename and I don't see anything off in the results

output.txt

[janosorcsik]

I tried the Refresh button, restarted my computer, and tried mdimport. I waited a few days in case indexing was still running, but I didn't see any change.