[vlc-devel] Re: Question about HD play

chshin chshin at netmedia.kjist.ac.kr
Thu Feb 5 22:22:33 CET 2004

> > But some problems still remains a mystery.
> > For reference, I linked two pictures captured.
> >
> >
> >
> >
> > These pictures captured during displaying HD(1080i) source with VLC.
> > As shown in pictures, their quality is not good. There are many broken
> > pixels.
> > I guess the rectangles are macro blocks and  UV processing has some
> > problems.
> > On low display resolution ( not media resolution ), decoding, displaying
> > were done well.
> > But on high display resolutions (eg. 2560 * 1024, 2304 * 864 .. etc),
> > quality is poor as pictures linked.
> > Even decoding work was unstable.
> What is the title of video window when the quality is like this?
> Also, is it
> different in the small resolutions when quality is good? Try
> disabling video
> overlay in the preferences, does this affect this problem? (It sure will
> give a nasty impact on performance).

As you expected, there is difference between messages!
hardware YUV overlay DirectX output  <-----------------  2048 * 768
software RGB DirectX output   <------------------ 2560 * 1024

I tried disabling video overlay. but it didn't affect this problem.
And tried change direcx output to GDI video output, then quality problem
But lost picture increased.

Does it say video card can not support overlay on high resolution? or ...
I don't know which one of video card and vlc makes trouble.

> > >What system resources? CPU? memory? io? My laptop has a P4M
> cpu at 2ghz,
> > and
> > >it is far from able to decode such a stream. But my 1.8ghz
> athlon XP can
> > >decode it fine. I talked with the libmpeg2 author and he
> thought perhaps it
> > >has something todo with L1 cache. Do the XEON have more L1 cache than a
> > P4M?
> > I meant CPU as system resource. During stream is displaying,
> cpu usage rate
> > was over 50%.
> > My XEON has 12KB L1 cache. (maybe intel P4M has 8KB)
> This is about the expected cpu usage on such a system. It takes
> some cpu to
> decode such a high resolution stream. I don't think other players
> manage to
> do this considerably faster than VLC.

I agree VLC is best of best player.
but, I really don't know why results are acquired like this  <----------------- test desktop <------ VLC  <-------- Media Player
As pictures say, cpu consumption of VLC is higher than MP's.
Could I know the reson of this phenomenon?


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