On Mon, Jan 04, 2016 at 05:38:46PM -0800, Ganesh Ajjanagadde wrote:
> On Sat, Jan 2, 2016 at 7:59 AM, Ganesh Ajjanagadde <gajja...@mit.edu> wrote:
> > On Sat, Jan 2, 2016 at 6:24 AM, Michael Niedermayer
> > <mich...@niedermayer.cc> wrote:
> >> On Fri, Jan 01, 2016 at 05:55:31PM -0800, Ganesh Ajjanagadde wrote:
> >>> On Wed, Dec 30, 2015 at 1:01 AM, Hendrik Leppkes <h.lepp...@gmail.com>
> >>> wrote:
> >>> > On Wed, Dec 30, 2015 at 4:39 AM, Ganesh Ajjanagadde
> >>> > <gajjanaga...@gmail.com> wrote:
> >>> >> The log is anyway rounded to an integer, so one may use an frexp
> >>> >> based approach. Note that this may be made frexpf; if arguments are
> >>> >> less than
> >>> >> 2^24 there is no loss. Kept as double precision for simplicity; 2^32 is
> >>> >> exactly representable as a double.
> >>> >>
> >>> >> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
> >>> >> ---
> >>> >> ffmpeg.c | 13 ++++++++++++-
> >>> >> 1 file changed, 12 insertions(+), 1 deletion(-)
> >>> >>
> >>> >> diff --git a/ffmpeg.c b/ffmpeg.c
> >>> >> index 6d01987..ee72f91 100644
> >>> >> --- a/ffmpeg.c
> >>> >> +++ b/ffmpeg.c
> >>> >> @@ -1486,6 +1486,17 @@ static void print_final_stats(int64_t
> >>> >> total_size)
> >>> >> }
> >>> >> }
> >>> >>
> >>> >> +static inline int log2i(double d)
> >>> >> +{
> >>> >> + int exp;
> >>> >> + double mant;
> >>> >> +
> >>> >> + mant = frexp(d, &exp);
> >>> >> + if (mant >= M_SQRT1_2)
> >>> >> + return exp;
> >>> >> + return exp-1;
> >>> >> +}
> >>> >> +
> >>> >> static void print_report(int is_last_report, int64_t timer_start,
> >>> >> int64_t cur_time)
> >>> >> {
> >>> >> char buf[1024];
> >>> >> @@ -1559,7 +1570,7 @@ static void print_report(int is_last_report,
> >>> >> int64_t timer_start, int64_t cur_ti
> >>> >> if (qp >= 0 && qp < FF_ARRAY_ELEMS(qp_histogram))
> >>> >> qp_histogram[qp]++;
> >>> >> for (j = 0; j < 32; j++)
> >>> >> - snprintf(buf + strlen(buf), sizeof(buf) -
> >>> >> strlen(buf), "%X", (int)lrintf(log2(qp_histogram[j] + 1)));
> >>> >> + snprintf(buf + strlen(buf), sizeof(buf) -
> >>> >> strlen(buf), "%X", log2i(qp_histogram[j] + 1));
> >>> >> }
> >>> >>
> >>> >> if ((enc->flags & AV_CODEC_FLAG_PSNR) && (ost->pict_type
> >>> >> != AV_PICTURE_TYPE_NONE || is_last_report)) {
> >>> >> --
> >>> >> 2.6.4
> >>> >
> >>> > This isn't exactly a performance critical area, and defining a custom
> >>> > function just for this seems somewhat like over-optimization.
> >>> > Just my opinion, of course, I'll leave the decision up to the
> >>> > maintainers of ffmpeg.c
> >>>
> >>> Ping: based on the above, final decision left to you, Michael.
> >>
> >> maybe av_log2() could be used, so as to avoid any increase in
> >> complexity
> >
> > Not really, or at least not without additional code. The lrint rounds
> > the log; av_log2 either returns the log of the next higher power of 2,
> > or the one before it. Thus they are quite different things. I don't
> > know if this is wrong or not; I created this to preserve identical
> > behavior.
>
> @Michael: final thoughts?is there any loss of usefullness of the output with av_log2() ? i dont think we need to maintain exactly identical output for such fancy / debug output [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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