[FFmpeg-devel] [PATCH] avcodec: use av_mod_intp2() where possible

[Michael Niedermayer]

On Tue, Apr 21, 2015 at 11:38:32PM +0200, Michael Niedermayer wrote:
> On Tue, Apr 21, 2015 at 05:45:25PM -0300, James Almer wrote:
> > Signed-off-by: James Almer <jamrial at gmail.com>
> > ---
> >  libavcodec/acelp_vectors.c     |  8 +++-----
> >  libavcodec/adpcm.c             |  2 +-
> >  libavcodec/alacenc.c           |  3 +--
> >  libavcodec/atrac3plus.c        |  4 ++--
> >  libavcodec/dnxhdenc.c          |  2 +-
> >  libavcodec/dvenc.c             |  2 +-
> >  libavcodec/ffv1.h              |  2 +-
> >  libavcodec/ffv1dec.c           |  3 +--
> >  libavcodec/g726.c              |  2 +-
> >  libavcodec/g729dec.c           |  2 +-
> >  libavcodec/golomb.h            |  2 +-
> >  libavcodec/h264.c              |  5 ++---
> >  libavcodec/h264_refs.c         |  2 +-
> >  libavcodec/hevc.c              | 26 ++++++++++++--------------
> >  libavcodec/hevc_cabac.c        |  8 ++++----
> >  libavcodec/hevc_filter.c       | 15 ++++++---------
> >  libavcodec/hevc_mvs.c          |  4 ++--
> >  libavcodec/hevc_ps.c           |  4 ++--
> >  libavcodec/hevc_refs.c         |  5 ++---
> >  libavcodec/hevcpred_template.c |  4 ++--
> >  libavcodec/mpeg12enc.c         |  8 ++++----
> >  libavcodec/opus.h              |  2 +-
> >  libavcodec/opus_celt.c         |  9 ++++-----
> >  libavcodec/proresenc_kostya.c  |  6 ++----
> >  libavcodec/put_bits.h          |  2 +-
> >  libavcodec/vorbisdec.c         |  5 ++---
> >  26 files changed, 61 insertions(+), 76 deletions(-)
> > 
> > diff --git a/libavcodec/acelp_vectors.c b/libavcodec/acelp_vectors.c
> > index 86851a3..7aef8c7 100644
> > --- a/libavcodec/acelp_vectors.c
> > +++ b/libavcodec/acelp_vectors.c
> > @@ -133,12 +133,11 @@ void ff_acelp_fc_pulse_per_track(
> >          int pulse_count,
> >          int bits)
> >  {
> > -    int mask = (1 << bits) - 1;
> >      int i;
> >  
> >      for(i=0; i<pulse_count; i++)
> >      {
> > -        fc_v[i + tab1[pulse_indexes & mask]] +=
> > +        fc_v[i + tab1[av_mod_uintp2(pulse_indexes, bits)]] +=
> >                  (pulse_signs & 1) ? 8191 : -8192; // +/-1 in (2.13)
> >  
> >          pulse_indexes >>= bits;
> > @@ -154,13 +153,12 @@ void ff_decode_10_pulses_35bits(const int16_t *fixed_index,
> >                                  int half_pulse_count, int bits)
> >  {
> >      int i;
> > -    int mask = (1 << bits) - 1;
> >  
> >      fixed_sparse->no_repeat_mask = 0;
> >      fixed_sparse->n = 2 * half_pulse_count;
> >      for (i = 0; i < half_pulse_count; i++) {
> > -        const int pos1   = gray_decode[fixed_index[2*i+1] & mask] + i;
> > -        const int pos2   = gray_decode[fixed_index[2*i  ] & mask] + i;
> > +        const int pos1   = gray_decode[av_mod_uintp2(fixed_index[2*i+1], bits)] + i;
> > +        const int pos2   = gray_decode[av_mod_uintp2(fixed_index[2*i  ], bits)] + i;
> >          const float sign = (fixed_index[2*i+1] & (1 << bits)) ? -1.0 : 1.0;
> >          fixed_sparse->x[2*i+1] = pos1;
> >          fixed_sparse->x[2*i  ] = pos2;
> [...]
> > diff --git a/libavcodec/ffv1.h b/libavcodec/ffv1.h
> > index 5081397..bfc4d71 100644
> > --- a/libavcodec/ffv1.h
> > +++ b/libavcodec/ffv1.h
> > @@ -143,7 +143,7 @@ static av_always_inline int fold(int diff, int bits)
> >          diff = (int8_t)diff;
> >      else {
> >          diff +=  1 << (bits  - 1);
> > -        diff &= (1 <<  bits) - 1;
> > +        diff  = av_mod_uintp2(diff, bits);
> >          diff -=  1 << (bits  - 1);
> >      }
> >  
> 
> iam not sure some of these changes are are a good idea
> for example above the mask has to be calculated anyway what can be
> gained from av_mod_uintp2() use here ?
> i think this should be bechmarked when its in performance critical code

but the changes look ok when it can be ensured theres no speed loss
or the code changed is not speed relevant

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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