Chapter images: add a small delay?

[chowbok 132]

Since with a lot of movies a chapter start corresponds with a fade-in, many chapter images are just plain black squares. It seems like a simple way to fix this would be to grab the chapter image from the chapter timestamp + 5 seconds or so. Is this something that seems feasible?

[Luke 42077]

how many seconds of black does your video have between chapters?

[chowbok 132]

Well, it's not just one video this is happening with. Older movies used fade-ins a lot. I tested from a few different movies, and it seems to be 3-4 seconds.

[hstamas 179]

Just started playing with chapter images myself and I’m seeing the same thing with TV shows. Episodes that have actual, designated chapter marks that Emby is honoring usually occur when the show is coming back from where a commercial used to live so there is a fade in from black. Most of my chapter images are capturing this black screen.

 

Example attached.

 

I thing a 1-2 second offset would solve the problem.

[Luke 42077]

what is your thumbnail interval setting on the server?

[hstamas 179]

what is your thumbnail interval setting on the server?

“Chapter markers”

[Luke 42077]

What container format is that?

[hstamas 179]

What container format is that?

Mkv

[Luke 42077]

Strange. We actually already use a filter to try and avoid black images on chapters.

[chowbok 132]

Strange. We actually already use a filter to try and avoid black images on chapters.

Really? I didn't realize that. It's not working for me, at least not always.

[Luke 42077]

Can you provide a sample video for testing? thanks.

[chowbok 132]

Too late to revive this thread? I have a good example file of what I was talking about, let me know if you'd still like to look at it and I'll put it up.

[Luke 42077]

Do you extract art chapters or the 10 second intervals?

[chowbok 132]

At chapters.

[Luke 42077]

OK, there is currently no option for this, but this idea has come up before and is possible for future updates. Thanks.

[Grimmer 15]

Would love this feature as well.

NCIS is a great example of this issue.  Pulling images at the chapter markers always results in a black screen (except for the first chapter):

A library level (and perhaps a TV show level override) of chapter mark + "X seconds" (and could accept + or - values).

 

Edited March 3, 2024 by Grimmer

[chowbok 132]

Just wanted to do an annual ping on this. It seems like just adding a 10–15 second delay on the chapter images would fix this, and be easy to implement.

[Grimmer 15]

Could also add a quick calculation to sum the values from a few hundred pixels across the chapter screenshot. If the sum is below a certain threshold (that indicates a black/dark scene), advance 1 sec and try again and repeat as needed. A small (negligible?) additional load on the CPU, but could keep the chapter screenshot as close as possible to the start of the chapter.

[chowbok 132]

I just feel that the more complicated this is, the less likely it is to be implemented. 

[Luke 42077]

We could always add a library option for this.

[chowbok 132]

That'd be fine with me.

[Grimmer 15]

Would it be possible to have the server admin choose the delay value in the library settings?  Is there already a default delay built in?  10-15 second is a very long time for video.  Skipping over a chapter fade-in, could likely be handled by a 2 second delay.

 

[Luke 42077]

43 minutes ago, Grimmer said:

Would it be possible to have the server admin choose the delay value in the library settings?  Is there already a default delay built in?  10-15 second is a very long time for video.  Skipping over a chapter fade-in, could likely be handled by a 2 second delay.

 

Yes. There currently is no delay. The image extraction uses a filtering technique to avoid getting black frames, however this is a push/pull because the more aggressive we make that, the more people complain that the extraction takes too long. But making that configurable could be an alternative to a delay because then you actually get an image that corresponds with the chapter timestamp.

[chowbok 132]

On 6/18/2025 at 10:59 AM, Grimmer said:

Would it be possible to have the server admin choose the delay value in the library settings?  Is there already a default delay built in?  10-15 second is a very long time for video.  Skipping over a chapter fade-in, could likely be handled by a 2 second delay.

 

You're right, 10–15 seconds is unnecessarily long. 3–4 would probably be ideal, I think 2 isn't enough.

I worry that Luke's proposed solution of auto-detecting black would take too long to implement.

Edited June 23, 2025 by chowbok
Submitted too soon

[chowbok 132]

Any luck with this? Still getting mostly black chapter images on my older movies.