Slow loading of black video thumbnails in MS Windows Explorer

I'm more curious as to why this might be happening rather than looking for an actual fix (because I don't think there would be one)....

I offload the video files from my dashcam's SD card to my computer every few days in case I need them at a later date. To save HDD space, I delete all the blank video files (video files that have been captured at night time with no content).

I've noticed that the thumbnails for these "blank" video files take significantly longer to load than the videos which contain action.

Is there a logical reason behind this?

>> MP4
>> H.264

Though I don't know the answer, I wanted to welcome you to the forum. I did ask the all-knowing AI the question and here's the answer I got.

There are a few technical reasons why all-black dash cam videos might take longer to load compared to action-filled ones:

• Compression & Encoding: Video files are typically compressed to save storage space. Action-heavy videos have varied frames, making compression more efficient. All-black frames, however, may be stored differently—sometimes with extra metadata or inefficient compression—causing longer loading times.
• File Corruption or Processing Issues: If your dash cam saves low-light or dark footage differently, the files may require additional processing when accessed.
• Frame Rate & Bitrate Differences: Some dash cams automatically lower the frame rate in dark scenes, affecting playback speed and requiring extra decoding.
• Storage Drive Read Speed: If your files are stored on slower memory cards or hard drives, loading certain video types might take longer.
• Software Optimization: Some video players struggle with handling large blocks of identical frames (like an all-black video), causing a delay when opening them.

Have you noticed this across multiple dash cams, or just with one specific camera? Could be an interesting quirk of the device!

See clearing thumbnails cache will help, you can also set thumbnail cache size is also an effective way to speed up Windows thumbnail loading.

Use the batch scripts to delete thumbnails cache.


To increase the thumbnail cache size, open the Command Prompt as an administrator and execute bellow command and reboot your computer.

glasskuter said:

Though I don't know the answer, I wanted to welcome you to the forum. I did ask the all-knowing AI the question and here's the answer I got.

There are a few technical reasons why all-black dash cam videos might take longer to load compared to action-filled ones:

• Compression & Encoding: Video files are typically compressed to save storage space. Action-heavy videos have varied frames, making compression more efficient. All-black frames, however, may be stored differently—sometimes with extra metadata or inefficient compression—causing longer loading times.

Click to expand...

The very first point made by AI regarding compression and encoding practices sounds more than sensible enough to be the answer to my question.

In related news, you'd think I'd know by now to run the question by a bot to see if an answer came to the fore before wasting other peoples time!

Thank you for taking the time and effort to comment, and thank you very much for your welcome !

FreeBooter said:

See clearing thumbnails cache will help, you can also set thumbnail cache size is also an effective way to speed up Windows thumbnail loading.

Use the batch scripts to delete thumbnails cache.

Click to expand...

I probably should have mentioned that I did try clearing the cache to see if it had any effect (I should also admit I cheated with 3rd party software).

To increase the thumbnail cache size, open the Command Prompt as an administrator and execute bellow command and reboot your computer.

Click to expand...

THAT I didn't know you could do.

Thank you for taking the time to comment and for teaching me something new!!

SnickoPen said:

In related news, you'd think I'd know by now to run the question by a bot to see if an answer came to the fore before wasting other peoples time!

Click to expand...

Posting questions and then having answers could help any number of people looking for something you have encountered.
It’s a positive, not a negative.