Tonemapping Filter Pull Request

[gallileo 1]

Hi there,

 

I have played around a bit with HDR tonemapping filters for ffmpeg.

 

I was wondering if you would accept a PR that adds a tonemapping filter to the MediaEncoding part of Emby? (As an alpha option of course)

 

Or would you accept a PR / help with creating one, that allows plugins to change the ffmpeg parameters / add filters?

 

Kind regards,

 

Leo

[Luke 36999]

Hi, this part of emby is not open source but can you give some examples of what you'd like to do? Thanks !

[gallileo 1]

Well as far as I can see, the part that generates the command line options for ffmpeg seems to be opensource here: https://github.com/MediaBrowser/Emby.Common/blob/master/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs?

 

I would like to add something like this as a filter (see the tonemap_opencl part):

 

ffmpeg -init_hw_device vaapi=va:/dev/dri/renderD128 -init_hw_device \opencl=ocl@va -hwaccel vaapi -hwaccel_device va -hwaccel_output_format \vaapi -i INPUT -filter_hw_device ocl -filter_complex \'[0:v]hwmap,tonemap_opencl=t=bt2020:tonemap=linear:format=p010[x1]; \[x1]hwmap=derive_device=vaapi:reverse=1' -c:v hevc_vaapi -profile 2 OUTPUT

This was taken from here: https://gist.github.com/Brainiarc7/4f831867f8e55d35cbcb527e15f9f116

 

From my testing this allows a hardware transcode at almost 2x speeds for full 4K blurays. And I am currently looking into speeding this up even more.

 

Ideally, (depends on how the options are integrated) one could even specify a different tonemapping filter (e.g. replace linear with hable, clip, etc.).

 

For the plugins, ideally, one could either override IMediaEncoding or EncodingHelper. This way, a plugin can specify custom parameters for ffmpeg, but this would probably need some more revamping.

[Luke 36999]

How do we detect when this should be applied?

[Guest asrequested]

And what if hardware acceleration wasn't being used? 

[gallileo 1]

@ I haven‘t yet looked at this in depth. I would imagine that we could use opencl anyways (just on the cpu), but I don‘t know.

 

@@Luke I would have an option to enable it. Then I would check that, as well as the color info from the media info that is already scanned into Emby (i.e. does it say bt2020).

[Luke 36999]

There is a performance impact to this, right?

[gallileo 1]

@@Luke Depends. When using hardware transcoding, there does not seem to be any performance impact, since the limit is hardware transcoding itself.

 

However, I haven‘t tried a lot with hardware transcoding on different gpus or a cpu. I suspect it would not impact it that much though.

 

If software decoding is used, I have no idea. If the tonemapping is done without opencl, I only get around 3-4 fps. However, even with software decoding, the opencl filter should be usable. But I do not know whether the software or opencl filter will be limiting there.

Edited November 26, 2018 by gallileo