[FFmpeg-devel] [PATCH 1/2] avcodec: Add AV_CODEC_FLAG2_FAST_UNSAFE, move unsafe uses of FAST to it

[Michael Niedermayer]

On Fri, May 29, 2020 at 02:22:03PM +0100, Kieran Kunhya wrote:
> On Fri, 29 May 2020 at 14:11, Michael Niedermayer <michael at niedermayer.cc>
> wrote:
> 
> > On Thu, May 28, 2020 at 11:57:38PM +0100, Kieran Kunhya wrote:
> > > >
> > > > More generally though (outside this unsafe flag case)
> > > > i do disagree with your argument a bit, performance does matter.
> > > > Iam regularly reminded of that for example, so much software becomes
> > > > slower on each upgrade with few if any features added the real users
> > > > care about. Just to pick one, the editor i use to write replies in mutt
> > > > is slower to close than before i upgraded the OS.
> > > >
> > > > Also again to stay general here, this does not apply to the unsafe
> > flag.
> > > > speed / cpu load does add up. Slower code means more CO2 emissions if
> > > > the software is used alot.
> > > > If you want a real example insetad of this flag where we could improve
> > > > IIRC there was some code iterating over options in the iteration over
> > > > options resulting in some sort of O(n^3) or so. Thats from memory
> > though
> > > > would need to check where that was exactly but thats something we
> > should
> > > > fix.
> > > >
> > >
> > > Please provide evidence that the H.264 Decoder has got slower.
> >
> > while, what you quote above was not about h264 at all
> > let me provide benchmarks of most fate h264 samples with and without
> > flag_unsafe
> > the script that made that is after it. a reply to the 2nd part of your
> > mail is
> > also below
> >
> 
> Yes, it's no surprise that a "fast" mode that violates the spec to produce
> some undefined and unsafe output is going to be faster.

this case does not violate the spec. The spec only describes a valid
bitstream. for valid bitstreams the h264 fast_unsafe case here is just 
faster, same output. 


> The responses are "aggressive" because many people want "fast" mode gone.
> 
> I also would like it gone and I think the consensus is there to remove it.

This still doesnt explain the aggressive tone we have here.
You know, one problem with this is when people are angry they
do not think as clear as when they are calm and there is the
risk that this leads to a different choice the same people would
have picked had they looked at the problem calmly.

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

If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
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