[FFmpeg-user] recent change to libavfilter hinders the movie filter to work on Windows

[Stefano Sabatini]

On date Tuesday 2011-11-01 10:45:57 +0100, PixelPartner encoded:
> Working with the following version under Windows 7 64
>  
> ffmpeg N-34031-ge403a97
> libavutil    51. 22. 0 / 51. 22. 0
> libavcodec   53. 23. 0 / 53. 23. 0
> libavformat  53. 17. 0 / 53. 17. 0
> libavdevice  53.  4. 0 / 53.  4. 0
> libavfilter   2. 45. 0 /  2. 45. 0
> libswscale    2.  1. 0 /  2.  1. 0
> libpostproc  51.  2. 0 / 51.  2. 0
>  
> There was recently a change that cripples the libavfilter movie= to accept Windows-Style file names.
> All of the following causes failure:

AFAIK there is no regression, there was no change in the way the movie
command is parsed.

> movie=C:\folder\file.ext
> movie=C:\\folder\\file.ext
> movie='C:\folder\file.ext'
> movie=C:/folder/file.ext
>  
> If I remove C: it works, but I assume it works only with files on the "current" drive.
>  
> It seems to me that someone added paramter parsing \\ -> \ and : for values also to the movie filter option list.
> Does this make any sense ?

A filename of this kind:
movie=C:\folder\file.ext

is de-escaped three times before to be used as a filename.
So you need to perform three level of escaping when providing such a
filename to libavfilter via commandline.

1. first escaping, de-escaping is performed by the movie filter
itself, will convert \X -> X, and will preserve strings between single
quotes.
movie=C:\folder\file.ext
->
movie='C:\folder\file.ext'

2. second escaping, de-escaping is performed when reading the movie
file description:
movie='C:\folder\file.ext'
->
movie=\'C:\\folder\\file.ext\'

3. third escaping, de-escaping is performed by your shell, in the case
of a bash shell:
movie=\'C:\\folder\\file.ext\'
->
"movie=\'C:\\\\folder\\\\file.ext\'"

I understand that all this is confusing and should be documented
better, but I see no other way to deal with strings which contain
characters which are special to the parsing function used
(libavutil/parseutils.h:av_get_token()).

Please tell if the attached patch is helpful to you.
-- 
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