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doc/filters: propose solutions to avoid shell escaping 

Reference drawtext textfile option and ffmpeg -filter_complex_script
and -filter_script as possible solutions to avoid shell escaping.

Address issue:
http://trac.ffmpeg.org/ticket/9008
This commit is contained in:
Stefano Sabatini 2023-03-26 17:47:52 +02:00
parent 030b34eac9
commit 7792f53e5e
2 changed files with 19 additions and 5 deletions
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2
doc/ffmpeg.texi
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@ -769,6 +769,7 @@ syntax.
See the @ref{filter_complex_option,,-filter_complex option} if you
want to create filtergraphs with multiple inputs and/or outputs.
@anchor{filter_script option}
@item -filter_script[:@var{stream_specifier}] @var{filename} (@emph{output,per-stream})
This option is similar to @option{-filter}, the only difference is that its
argument is the name of the file from which a filtergraph description is to be
@ -1978,6 +1979,7 @@ The default is the number of available CPUs.
Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or
outputs. Equivalent to @option{-filter_complex}.
@anchor{filter_complex_script option}
@item -filter_complex_script @var{filename} (@emph{global})
This option is similar to @option{-filter_complex}, the only difference is that
its argument is the name of the file from which a complex filtergraph

22
doc/filters.texi
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@ -282,6 +282,18 @@ previous string will finally result in:
-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
@end example
In order to avoid cumbersome escaping when using a commandline tool accepting a
filter specification as input, it is advisable to avoid direct inclusion of the
filter or options specification in the shell.
For example, in case of the @ref{drawtext,,drawtext filter}, you might prefer to
use the @option{textfile} option in place of @option{text} to specify the text
to render.
When using the @command{ffmpeg} tool, you might consider to use the
@ref{filter_script option,,-filter_script option,ffmpeg} or
@ref{filter_complex_script option,,-filter_complex_script option,ffmpeg}.
@chapter Timeline editing
Some filters support a generic @option{enable} option. For the filters
@ -12359,11 +12371,11 @@ braces is a function name, possibly followed by arguments separated by ':'.
If the arguments contain special characters or delimiters (':' or '@}'),
they should be escaped.
Note that they probably must also be escaped as the value for the
@option{text} option in the filter argument string and as the filter
argument in the filtergraph description, and possibly also for the shell,
that makes up to four levels of escaping; using a text file avoids these
problems.
Note that they probably must also be escaped as the value for the @option{text}
option in the filter argument string and as the filter argument in the
filtergraph description, and possibly also for the shell, that makes up to four
levels of escaping; using a text file with the @option{textfile} option avoids
these problems.
The following functions are available: