[FFmpeg-devel] [PATCH] avfilter/vf_overlay: fix alpha blending when main source has an alpha channel

Michael Niedermayer michael at niedermayer.cc
Tue Jul 18 14:33:50 EEST 2017


On Sun, Jul 16, 2017 at 08:26:57PM +0200, Peter Gro├če wrote:
> On Sun, 16 Jul 2017 18:33:33 +0200
> Paul B Mahol <onemda at gmail.com> wrote:
> 
> > 
> > how can one reproduce this bug?
> 
> ffmpeg -i fate-suite/mfx/track_01_v02.mxf -filter_complex \
> "movie=fate-suite/png1/lena-rgba.png[logo];[v:0][logo]overlay" -an -vframes 1 out.png
> 
> In this example files from the fate suite are used.
> 
> The source mxf file actually doesn't have an alpha channel, but the autoscaler adds one on adapting pixel formats:
> 
> [auto_scaler_0 @ 0x2118440] w:1280 h:720 fmt:yuv422p sar:1/1 -> w:1280 h:720 fmt:yuva420p sar:1/1 flags:0x2
> 
> As seen here [1] the png file has a almost zero alpha value on the left side, but the output is way too bright without the patch.
> 
> I hope this helps.
> 
> Regards
> Peter
> 
> [1] http://imgur.com/a/74ZF4

please also add a fate test for this

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Never trust a computer, one day, it may think you are the virus. -- Compn
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