[FFmpeg-devel] [PATCH] avfilter/interlace: prevent over-sharpening with the complex low-pass filter

Thomas Mundt tmundt75 at gmail.com
Thu Aug 31 23:40:12 EEST 2017

2017-08-31 21:42 GMT+02:00 Michael Niedermayer <michael at niedermayer.cc>:

> On Wed, Aug 30, 2017 at 03:54:08AM +0200, Thomas Mundt wrote:
> > Hi,
> >
> > we did a transcoding cascade test at work were over-sharpening became
> > visible with the complex low-pass filter. This patch rectifies the
> > behaviour.
> >
> > Please comment...
> did you perform subjective and or objective tests ?
> objective being some metric like PSNR vs correctly sampled data
> subjective being double blind tests with humans about which they prefer

The tests have been subjective with a team of video engineers and
technicians with several test files.

I did a quick SSIM/PSNR check with the first generation of an HD->SD file
as a reference against the 6th generation.
ffmpeg -i test.mxf -i ref.mxf -lavfi  "ssim;[0:v][1:v]psnr" -f null -
Results without the patch:
[Parsed_ssim_0 @ 041bef00] SSIM Y:0.956508 (13.615881) U:0.991601
(20.757750) V:0.993004 (21.551382) All:0.974405 (15.918463)
[Parsed_psnr_1 @ 03fc8440] PSNR y:31.838009 u:48.424280 v:48.962711
average:34.759466 min:31.699297 max:40.857847
Results with the patch:
[Parsed_ssim_0 @ 0424ed00] SSIM Y:0.970051 (15.236232) U:0.991883
(20.905857) V:0.993174 (21.658049) All:0.981290 (17.279202)
[Parsed_psnr_1 @ 0424f780] PSNR y:34.412108 u:48.504454 v:48.969496
average:37.264644 min:34.310637 max:42.373392

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