[FFmpeg-trac] #9531(undetermined:new): Unexpected ghosting around a transparent video encoded with hevc_videotoolbox
FFmpeg
trac at avcodec.org
Thu Nov 25 12:35:31 EET 2021
#9531: Unexpected ghosting around a transparent video encoded with
hevc_videotoolbox
-------------------------------------+-------------------------------------
Reporter: Chris | Type: defect
Patuzzo |
Status: new | Priority: normal
Component: | Version: git-
undetermined | master
Keywords: hevc | Blocked By:
hevc_videotoolbox apple |
transparent alpha |
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
'''Summary of the bug:'''
I am trying to convert two transparent videos from VP9 to HEVC so that I
can play them in Safari. They are both videos of some particle effects.
The first video that contains black pixels transcodes correctly. The
second video that contains blue pixels transcodes incorrectly. The alpha
values around the edges of the particles seems to be incorrect creating a
ghosting effect.
The video with blue particles was generated from the one with black
particles. I did this by mapping over each of the PNG files that were used
to create the videos and re-mapping the color from black to blue. I
believe I did this correctly. I can have attached one sample PNG of blue
and black to this ticket.
'''How to reproduce:'''
This transcode produces the correct result:
ffmpeg -c:v libvpx-vp9 -i black_particles.webm -c:v hevc_videotoolbox
-alpha_quality 1 -vtag hvc1 black_particles.mov
This transcode produces an incorrect result:
ffmpeg -c:v libvpx-vp9 -i blue_particles.webm -c:v hevc_videotoolbox
-alpha_quality 1 -vtag hvc1 blue_particles.mov
I have attached the '-report -v 9 -loglevel 99' output for both transcodes
as well as the input/output videos and screenshots that show the correct
and incorrect ghosting in Apple's video preview.
'''Build information:'''
I built ffmpeg yesterday from the master branch, commit
7e9e2cf93b6e22eaec72837ab59ac654c19b8d99. I used these parameters:
./configure --enable-libfdk-aac --enable-libvpx --enable-libvorbis
--enable-libx265 --enable-libx264 --enable-gpl --enable-nonfree
Many thanks
--
Ticket URL: <https://trac.ffmpeg.org/ticket/9531>
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