[FFmpeg-user] bitmap-subtitle in stream

Thomas Schmiedl thomas.schmiedl at web.de
Tue Jun 26 20:57:16 EEST 2018

Am 21.06.2018 um 12:09 schrieb Carl Eugen Hoyos:
> 2018-06-21 11:44 GMT+02:00, Thomas Schmiedl <thomas.schmiedl at web.de>:
>> Am 16.06.2018 um 19:03 schrieb Carl Eugen Hoyos:
>>> 2018-06-16 18:56 GMT+02:00, Thomas Schmiedl <thomas.schmiedl at web.de>:
>>>> I use ffmpeg on a router to restream a DASH-stream
>>>> (https://live.idnes.cz/slow/slowtv7_720p/manifest.mpd) to a local
>>>> htdocs-folder as HLS on the router. The media-server xupnpd2
>>>> reads the HLS and transfers it to the TV.
>>>> On the DASH-stream website
>>>> https://slowtv.playtvak.cz/prave-ted-mazaci-tramvaj-jede-prahou-d73-/mazaci-tramvaj.aspx?c=A150908_111659_mazaci-tramvaj_plap
>>>> is a map with the actual position of the tram. The router is to slow
>>>> for re-encoding using the video-filter "overlay".
>>>> Is it possible to integrate a bitmap-based subtitle in the generated
>>>> HLS-stream containing an actual map-image (e.g.
>>>> http://staticmap.openstreetmap.de/staticmap.php?center=50.05619,14.43873&zoom=15&size=800x300&maptype=mapnik&markers=50.05619,14.43873,ol-marker)
>>>> without re-encoding?
>>> In theory, you could provide subtitles but all formats are palettized
>>> and creating a palettized image also takes time. In any case, you
>>> would have to implement this programmatically.
>> Could someone provide a workflow how to do that programmatically. Until
>> now I have only worked with the ffmpeg-application in combination with
>> xupnpd2 mediaserver.
> Sorry, this is not something a beginner will be able to implement.
> The overlay filter is the only way to do this currently, its performance
> has been increased lately but that does not necessarily mean it will
> work on slow hardware.
> Carl Eugen
For a test, I exported a bitmap-subtitle in "Subtitle Edit" and run this 
ffmpeg (git-version) command:

ffmpeg -i 
-i sub.idx -i sub.sub -map 0:v -map 0:a -c copy -map 1 -c:s:1 
dvd_subtitle -metadata:s:s:1 language=eng -movflags 
frag_keyframe+empty_moov -bsf:a aac_adtstoasc -f mp4 -listen 1

The output from was served via 
Gerbera-mediaserver to a Panasonic-TV. The TV could not display the 
video and ffmpeg exited with "broken pipe".

I already asked this question in an other issue, but again: Could 
someone test this with a TV (maybe a different vendor) to find the 
required ffmpeg settings?

Thanks, THomas
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