FLOSS Multimedia Support in Fedora

[Martin Sourada]

On Mon, 2009-02-09 at 11:36 -0500, Gregory Maxwell wrote:
> 2009/2/9 Martin Sourada <martin.sourada at gmail.com>:
> [snip]
> > Yeah, I haven't too, though I sometimes produce something in mkv+theora
> > because e.g. there isn't a way how to add subtitle streams to ogg.
> 
> Thats not correct. For example, --subtitles argument to ffmpeg2theora
> takes a .SRT file and multiplexes it as Ogg/Kate.
> (http://wiki.xiph.org/index.php/OggKate)
> 
> (Thats a case where playback support is lacking in many tools— but it
> exists, is well specified, and isn't some kludge)
> 
Well, that is an interesting piece of software, but it seems to support
either image subtitles (big, binary, suboptimal for most modern use
cases) or purely text subtitles with none other effects than karaoke...
Well, at least some positioning and basic styling (font, color, borders
shadows) would make it an interesting alternative. Also there is AFAIK a
lack to attach fonts to the stream to make sure the subs will look the
same everywhere.

> > Putting video in ogg is suboptimal and if theora starts to get used more
> > widely, people will probably realize the need for full featured
> > containers like matroska for storing theora.
> 
> Matroska is reasonable, but 'suboptimal' really depends on your usage.
> Ogg is designed for real-time streaming and does that better than
> Matroska. Matroska is designed for non-linear access, can't be written
> in a single pass (AFAIK), and does non-linear access better. (For
> typical usage Ogg is lower overhead too, though the difference is
> small).  If you need to do piece wise editing, Matroska is vastly
> superior. For 'play a movie' purposes, the fundamental differences are
> small enough that most users will not care.
> 
Well I don't know the technical details so I can only nod my head... For
the play a movie purpose we see even .avi + xvid/divx are enough, this
part of mostly illegal community is slower to adapt better formats (e.g.
h264) and we probably won't gain this market share. The anime fansub
community on the other hand focuses mostly on quality and they
practically need support for ASS subtitles and H264 video streams (until
better codec appears) which means they need matroska. Kate would not be
an option for them. I don't think in our current position that we can
gain any significant market share either.

So basically we're left to amateur videos and screen-casts. In
screencast at least subtitle positioning is vital to be able to use the
subs effectively (you would not want to overlay your subtitles over some
important text in terminal).

> >> Some of the proprietary-codecs focused tools provide their own home
> >> grown implementations of the codecs (i.e. ffmpeg). These often do not
> >> implement the full spec, so its important to test their behaviour.
> >>
> > Last time I checked, ffmpeg contained open source but patent encumbered
> > codecs (i.e. not libre)... I don't think that classifies as proprietary.
> 
> Webster says:
> 
> Proprietary — something that is used, produced, or marketed under
> exclusive legal right of the inventor or maker  ; specifically : a
> drug (as a patent medicine) that is protected by secrecy, patent, or
> copyright against free competition as to name, product, composition,
> or process of manufacture
> 
[snip]
Ok, I see, better not nitpicking about words choice. Basically I wanted
to only point that in ffmpeg there are open source implementaiton of
both patent encumbered and not patent encumbered codecs but probably
there are not included any non-open-source implementations.


> I don't have tools to pick apart dirac streams as I do for Theora, but
> I'd put money on your 'lossless' dirac only being a lossless copy of
> the colorspace converted input.  Your RGB data was probably first
> converted into YUV 4:2:0 which has lower resolution for the color
> planes and can result in a slight loss of sharpness.
> 
Yeah, I suspected something like that as well. I don't understand
though, why you put the word lossless into quotes... There is an option
in dirac compression to use lossless algorithm [1] instead of the lossy
one. I rendered the video as well for private comparison, but due to its
bigger size (IIRC it was 36 MiB) I haven't included it in my
fedorapeople (also it's compatibility is same as that of the lossy
dirac).

Martin

References:
[1]
http://diracvideo.org/wiki/index.php/ParameterRateControl#Lossless_.283.29

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: This is a digitally signed message part
Url : http://lists.fedoraproject.org/pipermail/devel/attachments/20090209/8dc9a0fb/attachment.bin