[Ffmpeg-devel] H264 decoding problem

Michael Niedermayer michaelni
Thu Oct 12 23:39:18 CEST 2006


On Thu, Oct 12, 2006 at 07:58:07PM +0200, Michael Niedermayer wrote:
> > > Is there any indication that
> > > the problems are caused by a compiler bug? You don't even say what the
> > > problem is except "results in a grey picture". What good does attaching
> > > the "miscompiled" files do if that's all the problem description you
> > > give - do you think the gcc developers can check whether the produced
> > > code will "give a gray picture", except by building whole FFmpeg?
> > 
> > I'm sorry, but it's just that I'm so terribly stupid that I don't know
> > what else I can do at _this_ time.
> you could send me a compiled but not assembled h264.c ...
> 1. start with the case which generates a broken ffmpeg
> 2. rm h264.o ; make
> 3. copy and paste the line which compiles h264.o
> 4. replace -c -o h264.o by -S -o h264.s
> 5. send h264.s to me or upload it somewhere (its ~ 3mb)
> ill bet gcc ignored some of the asm constraints, at least thats what it
> does most of the time when it misscompiles some asm

ive checked through the cabac.h asms in the .s file and it seems gcc didnt
violate the constraints, so, sofar it seems that it was my fault not adding
"memory" to the clobber list which caused the bug

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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