Opened 5 years ago

Last modified 5 years ago

#6835 new enhancement

DVBSUB -> DVDSUB "blurring"

Reported by: Samuel Owned by:
Priority: normal Component: avcodec
Version: git-master Keywords: dvbsub dvdsub
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no


Summary of the bug:
The resulting DVDSUB seem to be "blurred", VLC and PotPlayer was used, and the subtitle position is different than the DVBSUB default one.

How to reproduce:
Here the source file used:
TS file of around 66 MB, link valid for 7 days.

% ffmpeg -fflags +genpts -i "F:\!MEDIA_TEST_FILES\UMS Video Testing Suite (20150121)\TESTS\INTERNAL SUBTITLES\20130718 2342 - NRK2 HD - Barnearbeid og slaveri.[0].ts" -map 0:v -map 0:a:0 -map 0:a:1 -map 0:s:0 -c:v copy -c:a:0 copy -c:a:1 copy -c:s dvdsub -f matroska testNadahar_dvbsubtitle2.mkv

Attachments (1)

ffmpeg-20171114-154813.log (1.0 MB ) - added by Samuel 5 years ago.

Download all attachments as: .zip

Change History (7)

by Samuel, 5 years ago

Attachment: ffmpeg-20171114-154813.log added


comment:1 by Samuel, 5 years ago

Summary: DVBSUB -> DVDSUBDVBSUB -> DVDSUB "blurring"

comment:2 by Carl Eugen Hoyos, 5 years ago

The resolution of the dvb subtitles is (approximately) 720x576, the video resolution is 1280x720. If you neither scale the subtitles nor the video, the subtitles will not correctly fill the screen.

comment:3 by Samuel, 5 years ago

Damn !!! i have totally missed that point. Thank you very much for your help :)
I tried -canvas_size 1280x720 and now the subtitle position is fine.

Still this weird DVDSUB blurring main issue though.

EDIT: Apply an aspect ratio correction of 960x720 to the canvas given the correct DVDSUB size. I'm too forgetful ;)

Last edited 5 years ago by Samuel (previous) (diff)

comment:4 by Carl Eugen Hoyos, 5 years ago

I don't know if there is a reason why dvdsub subtitles look very ugly while dvbsub subtitles look nice, even after re-encoding (to dvbsub).

comment:5 by Samuel, 5 years ago

Could that be related to the color/alpha palette conversion ?

Last edited 5 years ago by Samuel (previous) (diff)

comment:6 by Samuel, 5 years ago

I don't think that it is related to the blurry issue, but when inspecting, comparing the DVBSUB and DVDSUB i saw a frame size difference.
For example in the original DVBSUB, the first frame have a size of 434x46
But in the DVDSUB, it have a size of 439x41

All the others subtitle frames have around the same few pixels difference.

Last edited 5 years ago by Samuel (previous) (diff)
Note: See TracTickets for help on using tickets.