#11140: Subtitles blended into chroma-subsampled video contain unintended
stripes
-------------------------------------+-------------------------------------
Reporter: Oneric | Type: defect
Status: new | Priority: normal
Component: avfilter | Version: git-
Keywords: subtitles | master
ass | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
I’m forwarding this from https://github.com/libass/libass/issues/816
I was able to reproduce this myself using ffmpeg
719e46f54c0f3ea557503ec4cd5618332484f78a but it also occured on older
versions too; if this is a regression then not a too recent one.
When subs are blended by the subtitles/ass videofilter the sub overlay
bitmaps appear to get truncated to the video format’s chroma plane
resolution individually. This can cause issues e.g. with neighbouring sub
bitmaps whose border lies within a subsampled chroma pixel which will be
visible as jarring stripes. Those stripes are not present in video players
or authoring tools.
One possible fix is to first blend all subtitles into a single non-
subsampled RGBA surface and then convert this overlay as a whole to the
video’s format and blended onto the video frame.
Atm users can and must workaround stripes by first forcing the input video
to be converted to yuv444 or similar and then later convert back to the
desired format, e.g. yuv420
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11140>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
_______________________________________________
FFmpeg-trac mailing list
[email protected]
https://ffmpeg.org/mailman/listinfo/ffmpeg-trac
To unsubscribe, visit link above, or email
[email protected] with subject "unsubscribe".
