[FFmpeg-devel] RFC: -h message to stdout

[Nicolas George]

Hi.

The help message given by "ffmpeg -h" goes partially to stdout and partially
to stderr. More precisely, the part specific to ffmpeg goes to stdout, but
the help coming from lavc goes through av_log to stderr. I would like to fix
that, and I see several solutions:

1. The easiest: send everything to stderr. This is wrong: the help message
   is the normal, expected output of "ffmpeg -h". Furthermore, not all
   shells allow to pipe stderr to a pager as easily as "|& less".

2. The quick and dirty: dup2(2, 1).

3. Write a log handler that writes to stdout instead of stderr, and install
   it at the start of show_help.

4. Add a flag to av_log to write to stdout instead of stderr.

The solution 3 is probably the best, but 4 can be of some help for the
future. Furthermore, if I write a new log handler, maybe I could make it
public, so it can be reused.

Another question: while "ffmpeg -h" should certainly write to stdout, the
same is not true for "ffmpeg" alone. Does it matter?

Regards,

-- 
  Nicolas George
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