Re: [libdv-dev] Re: libdv for AMD64

[Roman S. <rv...@Su...>]

On Wed, Oct 27, 2004 at 09:47:58PM -0400, Dan Dennedy wrote:
> On Wed, 2004-10-27 at 00:13 -0700, Roman Shaposhnick wrote:
> > On Wed, Oct 13, 2004 at 07:03:35AM -0400, Dan Dennedy wrote:
> > > Thank you. I downloaded it, and will work on making sure it merges
> > > nicely into my CVS working copy and test. Then, hopefully we get some
> > > others to test.
> > 
> >   Well CVS obviously works on Opteron/SuSE 8. So that's covered. Now 
> >   for the bad news. For some reason it takes almost twice the time to
> >   decode pond.dv (8.7 user) compared to the ffmpeg with x86_64
> >   enabled DV decoder (4.7 user).
> 
> Dean did say it was not optimised for 64bit, just a minimal port. I
> expect ffmpeg to be better - both 32 and 64bit. The real comparison to
> be made is against --disable-asm. 

  I kinda lost you here. Why --disable-asm is important ? It's known
  to be way slower anyway.

> A user sent an e-mail after my
> announcement on kino forum, and said his system worked fine with the
> current libdv release. I told him that asm/mmx was disabled due to arch
> detection at configure. I asked him to try CVS, he did, and reported a
> huge performance gain, of course.

  Hm. I went and checked and I saw the following .o's under .lib/:

    dct_block_mmx_x86_64.o
    encode_x86_64.o
    idct_block_mmx_x86_64.o
    quant_x86_64.o
    rgbtoyuv_x86_64.o
    transpose_x86_64.o

  so it would seem that x86_64 support gets used.

> Also, Kino's bugtracker http://jira.schirmacher.de/ contains a segfault
> with backtrace bug report of an amd64 user using kino compiled against
> libavcodec. It should be easy to spot in the list. However, it contains
> no libavcodec version indication. As a matter of fact, that sort of
> thing is rather hard for users to track and report as many ffmpeg users
> are not using an official ffmpeg release.

  Interesting. Of course ffmpeg's stable release is long overdue, but
  CVS should be quite stable as far as DV is concerned. Are you sure
  that it failed in DV decoding, not when user tried to export stuff
  into mpeg4 or something.

  Anyway, tomorrow I'll give it a try on my Opteron box.

Thanks,
Roman.

P.S. Of course I'm biased, but it seems that Sun manufactures a real killer
Opteron boxes...