[FFmpeg-trac] #3253(avfilter:closed): drawtext filter: problems with text expansions

[FFmpeg]

#3253: drawtext filter: problems with text expansions
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             Reporter:  Krieger      |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:  avfilter
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
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Changes (by beastd):

 * status:  new => closed


Comment:

 Replying to [comment:7 Cigaes]:
 > Replying to [comment:4 beastd]:
 > > I cannot exactly explain how all this works together, but it seems
 that you need to deal with another layer of escaping or in other words add
 another \ . Then it works as expected here.
 >
 > You escape once for the {{{drawtext=...}}} option and the parsing until
 the comma, and a second time for the {{{text=...}}} value and the parsing
 until the colon before fontfile.

 Yes, that should be correct.

 So it can be concluded that drawtext function evaluation has nothing to do
 with this.

 To examine this exact example:
 The single quotes take the shell out of the game (assuming you use a
 POSIX-ish shell; I do).
 So I will omit them and the additional parameters below.
 Now we have this:
 {{{
 drawtext=text=%{expr:t},
 }}}
 It won't work because the drawtext filter's arguments are parsed and the
 colon will
 be seen as delimiter.
 {{{
 drawtext=text=%{expr\:t},
 }}}
 This looks like it would do the trick and escape the colon, but it fails
 because the
 backslash is removed on the first pass. The second pass again interprets
 the colon as
 a delimiter and things go wrong.
 {{{
 drawtext=text=%{expr\\:t},
 }}}
 works because at the first pass the double backslash is substituted with a
 single
 backslash and that single backslash escapes the colon on the second pass
 which parses
 the drawtext filter's arguments.

 Therefore I close this ticket now. Please re-open if suggested solution
 does not work
 for you.

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Ticket URL: <https://trac.ffmpeg.org/ticket/3253#comment:8>
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