Re: [FFmpeg-devel] [PATCH 2/3] avcodec/j2kenc: Add alpha support

[Michael Niedermayer <michael@niedermayer.cc>]

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On Wed, Apr 05, 2023 at 02:50:46PM +0200, Tomas Härdin wrote:
> sön 2023-04-02 klockan 23:34 +0200 skrev Michael Niedermayer:
> > On Fri, Mar 31, 2023 at 01:14:40AM +0200, Michael Niedermayer wrote:
> > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > > ---
> > >  libavcodec/j2kenc.c | 28 ++++++++++++++++++----------
> > >  1 file changed, 18 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c
> > > index 97b0da1c976..b23fb73770a 100644
> > > --- a/libavcodec/j2kenc.c
> > > +++ b/libavcodec/j2kenc.c
> > > @@ -320,8 +320,8 @@ static int put_siz(Jpeg2000EncoderContext *s)
> > >  
> > >      for (i = 0; i < s->ncomponents; i++){ // Ssiz_i XRsiz_i,
> > > YRsiz_i
> > >          bytestream_put_byte(&s->buf, s->cbps[i] - 1);
> > > -        bytestream_put_byte(&s->buf, i?1<<s->chroma_shift[0]:1);
> > > -        bytestream_put_byte(&s->buf, i?1<<s->chroma_shift[1]:1);
> > > +        bytestream_put_byte(&s->buf, (i%3)?1<<s-
> > > >chroma_shift[0]:1);
> > > +        bytestream_put_byte(&s->buf, (i%3)?1<<s-
> > > >chroma_shift[1]:1);
> > 
> > i will replace the %3 by +1&2 to avoid slow modulo before applying
> 
> Is the compiler not smart enough to do that automagically? Not a biggie
> though

It seemed better to not depend on that as both variants are otherwise similar
I didnt check if the compiler can remove the modulo

thx

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

If the United States is serious about tackling the national security threats 
related to an insecure 5G network, it needs to rethink the extent to which it
values corporate profits and government espionage over security.-Bruce Schneier

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