[FFmpeg-devel] [PATCH] swscale-test: add md5 output

[Michael Niedermayer]

On Sat, Jul 24, 2010 at 07:52:03PM +0200, Reimar D?ffinger wrote:
> On Sat, Jul 24, 2010 at 06:43:20PM +0100, M?ns Rullg?rd wrote:
> > Ramiro Polla <ramiro.polla at gmail.com> writes:
> > 
> > > On Fri, Jul 23, 2010 at 9:59 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > >> On Fri, Jul 23, 2010 at 06:54:15PM -0300, Ramiro Polla wrote:
> > >>> $subj, to be used for regression tests. sse is still default.
> > >>> (indentation will be done afterwards)
> > >>
> > >> knowing how similar the output is to the input is usefull as well as its
> > >> usefull to know if they differ on 2 computers
> > >
> > > -sse is still left as an option to be run separately, or do you want
> > > both strings to be printed out?
> > >
> > >> btw, crc should be slightly faster than md5...
> > >
> > > New patch attached used av_adler32_update().
> > 
> > Wasn't it just recently someone advocated sha1 over md5 (in the
> > context of the md5 muxer iirc), the latter allegedly not strong
> > enough?

feeding the troll ...
md5 is intended to be a strong hash, "recent" advances in cryptanalysis
made it somewhat weak, thus replacing md5 by something better in the
contect where md5 was needed makes sense.

crc is intended to detect changes in data though damage or simply to
detect that data differs, not intentional tampering, iam not aware of
advances in random noise in this universe that weakens crc

besides adler32 is actually significantly weaker than crc32 for small
packets of data, i dont know if this applies to us here


> 
> IMO that was more a theoretical discussion.
> I did argue that a CRC is not really enough for e.g. a muxer
> which calculates a single number for a full file.
> I can't imagine it really matters much for rather limited
> regression tests on not that much data and where you always
> run more than just one single test so going for speed seems
> reasonable (though I guess only of there's actually a relevant
> speed difference).

how often did we or anyone had crc32 colissions that hid bugs?
statistically that should happen less ofthen than once every
4 billion bugs


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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