[FFmpeg-trac] #9453(undetermined:new): Overlay with negative x/y produces artefacts

FFmpeg trac at avcodec.org
Thu Oct 14 14:29:31 EEST 2021


#9453: Overlay with negative x/y produces artefacts
-------------------------------------+-------------------------------------
             Reporter:  Jozef        |                    Owner:  (none)
  Chutka                             |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  4.3.2        |               Resolution:
             Keywords:  overlay      |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Description changed by Jozef Chutka:

Old description:

> Summary of the bug:
>
> Overlaying image/movie over main with alpha channel (see [shape])
> produces ugly artefacts esp. when used with negative x/y.
>
> However, when color=c=0x000000 (no alpha) or x/y is positive there are no
> visible artefacts.
>
> How to reproduce:
>
> {{{
> ffmpeg -filter_complex_script filter.txt -frames:v 1 out.png -y
> }}}
>
> filter.txt:
>
> {{{
> color=c=0xff0000:size=1280x720[main];
> color=c=0x00000000:size=500x500[shape];
> movie=640x640.jpg,[shape]overlay=y=-10,[main]overlay
> }}}

New description:

 Summary of the bug:

 Overlaying image/movie over main with alpha channel (see [shape]) produces
 ugly artefacts esp. when used with negative x/y.

 However, when color=c=0x000000 (no alpha) or x/y is positive there are no
 visible artefacts.

 How to reproduce:

 {{{
 ffmpeg -filter_complex_script filter.txt -frames:v 1 out.png -y
 }}}

 filter.txt:

 {{{
 color=c=0xff0000:size=1280x720[main];
 color=c=0x00000000:size=500x500[shape];
 movie=640x640.jpg,[shape]overlay=y=-10,[main]overlay
 }}}

 Actually using ffmpeg 4.4, but this version is not avialble in version
 dropdown in this form.

--
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Ticket URL: <https://trac.ffmpeg.org/ticket/9453#comment:1>
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