[FFmpeg-devel] [PATCH v1] avcodec/utils: use av_rescale()

[lance.lmwang at gmail.com]

On Sun, May 03, 2020 at 03:10:09PM +0200, Andreas Rheinhardt wrote:
> lance.lmwang at gmail.com:
> > On Mon, Apr 20, 2020 at 07:00:55PM +0800, lance.lmwang at gmail.com wrote:
> >> From: Limin Wang <lance.lmwang at gmail.com>
> >>
> >> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> >> ---
> >>  libavcodec/utils.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> >> index 26c038dfd9..005d596dfd 100644
> >> --- a/libavcodec/utils.c
> >> +++ b/libavcodec/utils.c
> >> @@ -2229,8 +2229,8 @@ int64_t ff_guess_coded_bitrate(AVCodecContext *avctx)
> >>          const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
> >>          bits_per_coded_sample = av_get_bits_per_pixel(desc);
> >>      }
> >> -    bitrate = (int64_t)bits_per_coded_sample * avctx->width * avctx->height *
> >> -              framerate.num / framerate.den;
> >> +    bitrate = av_rescale(avctx->width * avctx->height,
> >> +                bits_per_coded_sample * framerate.num, framerate.den);
> 
> Is this supposed to be a cosmetic patch or do you have a testcase where
> it leads to better results? Anyway, bits_per_coded_sample *
> framerate.num might overflow (the function parameter is 64bit, but the
> calculation will nevertheless be performed as int * int).
> (I am not saying that the overflow checks for the code as-is are
> perfect, as I don't know what checks have already been performed to make
> sure that the calculation doesn't overflow an int64_t; but you would add
> a new possibility for overflow.)
> 
> And your indentation is off: the second line (i.e.
> bits_per_coded_sample) should be aligned with the first function
> parameter in the first line (i.e. avctx->width).

Sorry, my mistake, I ping another patch in fact. please ignore the patch.


> 
> - Andreas
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-- 
Thanks,
Limin Wang