[MPlayer-dev-eng] [DOCS] [3rd try] missing option descriptions

[D Richard Felker III]

On Mon, Aug 25, 2003 at 02:00:37AM +0200, Arpi wrote:
> > - (no)autoexpand
> > 
> >   Rich made some mysterious rumbling about this being a very obscure
> >   option that was added for some encoding work he needed to do and he
> >   was unsure whether such a hack should be documented at all..  I'd
> >   say document or remove, so I guess we should go for the former.
> 
> ok this is not easy.
> as you probably know, OSD rendering in g1 is handled by vo drivers.
> (it has historical reasons, osd existed before filter layer).
> but mencoder doesnt use libvo, but users still want osd rendering with it,
> to render subtitles into the encoded avi (which is silly anyway).
> to workaround this, mencoder by default inserts the 'expand' video filter,
> which can do the osd rendering. but since we support slices, and DR and some
> other tricks has been done in vf_expand, sometimes it's broken/buggy/slow,
> so it's better not inserting it at all. so, to avoid auto-inserting expand
> filter in mencoder, you can use -noautoexpand

Yes, Arpi is mostly right about this, but it has another use. IMO,
subtitles look MUCH better when rendered at high resolution then
scaled by swscaler, as opposed to rendered at low res. So when I was
making small encodes with hardcoded subs for hopeless WMP users who
can't figure out how to install the .srt filter or whatever :))))) I
wanted to render subs at the beginning of the filter chain rather than
the end. However, mencoder's auto-inserted vf_expand always renders
subs, so it was double-rendering them, and doing it in a bogus manner
since the OSD code does not support multiple instances (image/font
size are initialized only once)... The only clean way I found around
this problem was to allow the user to disable the auto-inserted expand
filter.

Anyway I have no idea how this should be documented. Feel free to
summarize what Arpi and I said for the man page, but I really don't
think it deserves that much attention, since it's only useful if
you're doing something lame (burning subtitles into your movie).

Rich