[MPlayer-dev-eng] key frame extractor / vo_jpeg use YV12 instead of RGB patch

[Reimar Döffinger]

Hello,
On Fri, Mar 16, 2007 at 01:25:24AM -0700, Trent Piepho wrote:
> On Thu, 15 Mar 2007, Andreas Krebs wrote:
> > this is how far I got, however this already created some interesting results, so vo_jpeg
> > now runs almost twice as fast on my PC, simply to the fact the it now directly uses
> > YV12 rather than converting to RGB and back, also  the image quality seems to have
> > improved a bit by this (at least the resulting jpegs look better to me - but maybe it's
> > only my imagination ;-) ).
> 
> It's much better to do it this way, sending YUV to libjpeg rather than converting
> to RGB and then having libjpeg convert back to YUV.
> 
> You are not doing it quite right though.  The YUV data in video formats is
> almost never full range, but has something called ccir r.601 excursions.
> JFIF standard jpegs on the other had have full-range yuv data.  So, you
> must convert one to the other if you want to create standard jpeg files.

IMO just keep the current RGB support and ignore this issue. Anyone who
really cares can still add -vf format=rgb24 and everyone else gets the
fasted dumping. In addition IIRC these "incorrect" jpegs will actually
me played correctly with mf:// and when stuffed into an MJPEG, whereas
real JPEGs will not, so it's questionable if such a conversion would be
desirable currently anyway.

Greetings,
Reimar Döffinger