[FFmpeg-devel] RFC: setting format parameters from the URL

[Nicolas George]

Hi.

Some format require that various parameters are already set before the call
to av_open_input_file. This happen for raw format that lack sufficient
headers, for capture formats, and sometimes when format detection fails.

If an application wants to support these formats, it needs to implement some
way for the user to specify these parameters. I find this is a case of
reinventing the wheel, with all related problems: some application will
implement some parameters and not others, new parameters will only be
supported in new applications, etc.

A convenient solution to this problem would be for av_open_input_file to be
able to find these parameters in the user-given URL.

There is a similar feature in ImageMagick: the user can specify PNG:- to
write a PNG to a pipe, or X: to grab an image from the X11 server, and it
works automatically with any application using the libMagick API. This is
very convenient.

Before I start to hack something, I would like some advice. Would it be
considered an useful feature? And if so, the actual syntax needs to be
devised carefully; I have a few ideas for that point, but nothing completely
satisfactory. Any advice?

Regards,

-- 
  Nicolas George
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