[FFmpeg-trac] #2631(avfilter:open): fade filter offset from the end of stream

[FFmpeg]

#2631: fade filter offset from the end of stream
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             Reporter:  burek        |                    Owner:
                 Type:  enhancement  |                   Status:  open
             Priority:  wish         |                Component:  avfilter
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by richardacre):

 Suggest a more flexible approach would be to allow a negative start-frame
 to count back from the end but also allow the second parameter to be
 omitted to also signify "from here until the end" ... so that in the 200
 frame video example (above) the following would all have the same effect:

 fade=out:155:45
 fade=out:-45:45
 fade=out:155
 fade=out:-45

 Same timekeeping could also apply to any filter (e.g. show a watermark for
 final X frames and audio fades)

 This would certainly help me, as I am currently tasked with watermarking
 and processing several dozen videos and would love to be able to automate
 all of it in one simple script, rather than having to determine the length
 of each clip and then tailor the parameters individually!

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2631#comment:2>
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