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
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