TM for Chapter Thumbnails ...

[rbjtech 527]

So a question for @softworkz most likely.

I've been playing around with ffmpeg with the TM filters trying to get Tone Mapped chapter thumbnails created in the .bif's.

I can't seem to use the TM filter in the image extractor in ffmpeg - ffmpeg is reporting that this function cannot use the filter.

I have got it 'working' if I simply do a TM conversion to a thumbnail resolution video (to rapidly increase it's conversion speed) and then re-run the thumbnail extract on that to produce the 'SDR/tone mapped' images.  Then delete the TM video file.

I was hoping to do it all in a single ffmpeg command.

It's obviously not urgent - but the 'washed out' thumbnail images on an SDR display are nagging me .. 

Any thoughts ?

  

Edited February 19 by rbjtech

[rbjtech 527]

So @cayars reminded me that you can just use filter with tone mapping on the existing ffmpeg command line - but this is CPU only -

ffmpeg.exe -f matroska -skip_interval 30 -copyts -i file:"input.mkv" -vf "zscale=transfer=linear,tonemap=mobius,zscale=transfer=bt709" -an -sn -s 320x180 -vsync cfr -r 0.1 -f image2 "C:\temp\img_%05d.jpg"

For the time being, I may just script rebuilding my 4K library with these newly generated bif's using biftool to create them.

Down the line, I guess it would be nice for the image extractor to look at the colour space and apply the filter as necessary - I don't believe it  uses h/w acceleration today ?  So this is probably not a big deal to just include the optional TM filter.

  

 

 

 

[cayars 1890]

Hey I hope it takes you a long, long time to create the bif files.

You have lots of 4K media then.

I don't think this will be as bad as you think, fingers crossed.

[rbjtech 527]

So @softworkz has been busy in the background .. 

Looking at the ffmpeg command line in the logs, it appears the new beta is applying a gamma/saturation filter to attempt to correct the SDR/HDR issues.

My thoughts are it certainly looks better than no TM, but it's possibly too dark imo.

I've put the 3 methods below - top row is no TM, middle row is using TM/Mobius, bottom row is gamma/sat filter,

Personally, I think the middle row looks the best by far.

I'll do some more research on this to look the cpu load of a gamma/sat filter vs doing a proper (cpu) TM - as from my initial look, there wasn't much difference.

 

 

Edited Tuesday at 11:08 AM by rbjtech

[softworkz 796]

Check out the next version, should be a bit brighter. Also check with multiple different videos.

The current is a quick and lightweight solution. It has taken great effort to achieve the quick image extraction that we have and I don't want to unnecessarily load it with something that adds again. We'll see how it works out and revisit this subject if it doesn't.

BTW: HW acceleration for image extraction is totally pointless (for our quick-image-extraction at least). I've explained the background somewhere here in the forums.