Disabled by default. Enable it with the "mediacodec-audio" option.

Add ParseVideoExtra that parse video extra data for h264/hevc.
Leave room for a possible ParseAudioExtra.

Rename DecodeVideo to DecodeCommon.

DecodeCommon use 2 callbacks to put Video and Audio specific code. These
callbacks are called when a new block is processed and when it try to get an
output buffer.

Add an union for future audio arguments.

It happens when fetching the "channel-mask" property.

Disabled since it's not tested enough.

Also, fix it.

The current workflow is often parsing a subtitle format, then convert it
in a common HTML and then push it to the renderer as HTML. The renderer
will reparse the HTML and try to render it. Of course, that means that
only one renderer can do that correctly, and so we bloat the freetype
renderer as much as we can.
It also means that we have 2 render callbacks for subtitles, one for
normal text and one for styled text, and we sometimes reparse the HTML
to remove the tags, for the first.

We now only use a text_segment, with new segments at every style change;
an unique render function and the renderer can decide to honor or not
the style.

It's a big commit, so regressions can arise, but it was tested for most
common cases.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>