diff filter complementing preview function

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Djfe
Bright Spark User
Posts: 178
Joined: Tue May 13, 2014 8:01 pm

diff filter complementing preview function

Post by Djfe »

I have suggestion:
A diff filter to be able to see/guess better at how much you loose from compressing the video
similar to this:
http://forum.doom9.net/showthread.php?p=1635801 (I know this is a filter to compare different resolutions, which isn't the same, I'm just using it as an example)

what do you think of this?

Is it to hard to show which changes are significant enough?
(since codecs influence many pixels, without you being able to notice it)

I don't know if the libav implementation used by hb already has these kinds of filters, but maybe it's enough to generate some diffs between original and newly encoded video on-the-fly
it might not even require much code, in-case it's something that you could get with a oneline commandline from tools like ffmpeg
but it still might be useful to some

EDIT:
this might also be useful to do before compression for filters like NL-means
to see whether your settings are affecting too many details

Woodstock
Veteran User
Posts: 3366
Joined: Tue Aug 27, 2013 6:39 am

Re: diff filter complementing preview function

Post by Woodstock »

"How much you lose" is a very subjective metric, especially when dealing with video that has many different types of scenes in it.

Some settings favor maintaining detail, some favor properly rendering fast motion, etc.

Some settings favor dark backgrounds, others favor backgrounds with more dynamic lighting ranges.

Your mention of NL-means is an example - some videos use background "noise" for artistic effects, usually limited to a few scenes, and any setting changes you make would not be visible unless you were comparing one of THOSE scenes.

Djfe
Bright Spark User
Posts: 178
Joined: Tue May 13, 2014 8:01 pm

Re: diff filter complementing preview function

Post by Djfe »

yes, but if it's video footage from your camera, that usually won't be the case

it might not make sense for encoding movies

I got footage from a friend that he recorded with a cheap cam on his helmet while skying.
720p avi mjpeg 30fps 25mbit/s
and it looks like the sensor resolution might be a bit lower than 720p
I want to maximize the compression

Right now I'm doing it visually, but some real values would make it easier to compare

about nl-means:
in-case your videos are cartoons, then a diff should work perfectly fine: it should only contain something like gaussians noise

for film it might be different (I know several movies that got recorded partially in 16mm (intentionally)), but in that case it's up to your settings in any case ^^
even without the diff

musicvid
Veteran User
Posts: 3441
Joined: Sat Jun 27, 2009 1:19 am

Re: diff filter complementing preview function

Post by musicvid »

A difference filter, although visual, is a lousy metric for temporal measurements, and shouldnt be used with program source, which is already a moving target

A better idea would be to resurrect PSNR, maybe add SSIM in Handbrake, although we already know HB is lossy by design.

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JohnAStebbins
HandBrake Team
Posts: 5502
Joined: Sat Feb 09, 2008 7:21 pm

Re: diff filter complementing preview function

Post by JohnAStebbins »

You can still get PSNR and SSIM metrics in the log by enabling the respective encoder tune option. Those numbers don't mean much without the tune enabled, so we disable them in the logs when the tune isn't selected.

musicvid
Veteran User
Posts: 3441
Joined: Sat Jun 27, 2009 1:19 am

Re: diff filter complementing preview function

Post by musicvid »

Thanks!

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