Format is based on the thread:
"[PATCH] doc/encoders: Add libopus encoder doc" (06-28-2013)
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/165368/

Also merge the two option sections (Mapping and Private options).

Patch partially edited by Stefano Sabatini.
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

Enhance consistency.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Adapted from the author's blag.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Signed-off-by: Diego Biurrun <diego@biurrun.de>

CC: libav-stable@libav.org

Signed-off-by: Ivan Pozdeev <ivan_pozdeev@mail.ru>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

max-intra-rate / force_key_frames, forgotten in 695e85f1, cb7f0622.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

tune, fastfirstpass and profile are not available through x264opts.
Since some FFmpeg options don't match the names used in libx264, add
libx264 option names as a reference when needed. And last thing, x264
don't have a manpage ATM, so prefer the x264 --fullhelp over the
unexistant manpage reference.

some of the mode values were reversed

Documents the mapping from FFmpeg options to libvpx.

Floating-Point-Only section was added after the video encoders chapter
in 034fc7bf merge.

Having a separate section for audio encoders simplifies navigation
and is slightly more consistent with the rest of the manual.
Signed-off-by: Diego Biurrun <diego@biurrun.de>

Channel coupling is an optional AC-3 feature that increases quality by
combining high frequency information from multiple channels into a
single channel. The per-channel high frequency information is sent with
less accuracy in both the frequency and time domains. This allows more
bits to be used for lower frequencies while preserving enough
information to reconstruct the high frequencies.

Also remove -x264opts item from the ffmpeg manual, since it belongs to
the encoders section.

Make Audio Encoders a separate chapter, and decrese the contained
sections level by one.

Improve rendering, and improve consistency with the other parts of the
manual.

This reverts commit f8a45fa1.

Conflicts:

	doc/optimization.txt

unless it stands for ffmpeg the program or is historic

Signed-off-by: Janne Grunau <janne-ffmpeg@jannau.net>
(cherry picked from commit 0fa904c9)