[MPlayer-dev-eng] MPlayer GSoC ?

Wed Feb 25 16:14:11 CET 2009

A way to set the Subtitle Font and the Subtitle File Encoding. Let me
think on this some more.

>> or a way to use mplayer as a
>> library so the slave interface is not needed.
> 
> What would be the advantage of an library interface for you?
> What problems would it solve?
> 

Well I agree there are advantages and disadvantages to this, but
probably the biggest thing is knowing what features are available. Right
now when debugging problems, the first question is almost always 'What
version of mplayer are you using'. Normally it is 1.0rc2 when there are
subtitle issues. So having it as a lib would help knowing what features
I could enable at compile time (ASS support, FreeType, what ao's and
vo's are available). Right now I can detect some of that (for example I
test for the -volume option since it is useful, but most people's
mplayer is to old and so they don't have it)

>> Common requests I get are
>> 'gapless' playback and the ability to change outputs and subtitle
>> options without restarting mplayer.
> 
> Changing vo and ao during playback is currently not supported by
> the design of MPlayer. Though it should not be too difficult to add.
> 

Not a big worry to me at all, personally I think most people find a vo
or ao that works (or even accept the default) and they are done.

>> I'm guessing the outputs would be
>> impossible, but the subtitle options might be an area to look at.
>> Another would be to be able to adjust some of the filters like crop
>> without restarting.
> 
> Subtitles and vf options changes should be possible... though there
> is no interface exported in MPlayer IIRC. Ie the vf chain would need
> to be reinitialized.
> 

Even adding or removing filters via the slave interface might be
interesting. Even if chain had to be flushed and recreated.

A couple of features/limitations that would be nice to have fixed.

On DVDs w/o dvdnav and the -identify flags is used, in the output from
mplayer I'll get something like this

ID_AUDIO_ID=128
ID_AID_128_LANG=en

Which helps identify the aid with a language code and allows me to put a
user understandable label on a menu. When I use dvdnav on the same disk,
only the ID_AUDIO_ID is output leaving me to put just the numeric value
in the menu. So having the language tag is useful. I've also seen this
on some quicktime files as well (lavfpref demuxer).

Another is the ID_ tags that are output. I use them alot in
gnome-mplayer to gather the details of the media being played. If the
video aspect is reported as 0.0 can it be calculated? An example output
with the -identify flag.

ID_DEMUXER=lavfpref
ID_VIDEO_FORMAT=avc1
ID_VIDEO_BITRATE=0
ID_VIDEO_WIDTH=848
ID_VIDEO_HEIGHT=352
ID_VIDEO_FPS=23.976
ID_VIDEO_ASPECT=0.0000
ID_AUDIO_FORMAT=255
ID_AUDIO_BITRATE=0
ID_AUDIO_RATE=48000
ID_AUDIO_NCH=6
ID_LENGTH=99.16
ID_SEEKABLE=1
ID_CHAPTERS=0

There is no reason why ASPECT should be 0.0 in this case since the width
and height are known. Also in the output the AUDIO bitrate eventually is
output again correctly, but the video bitrate is never updated. I
realize these values probably change during playback with variable
bitrate files, but outputting some value other than 0 is useful.

Thanks for listening,

Kevin
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