[FFmpeg-devel] [PATCH] avformat/movenc: Explicitly address potential division by zero.

Lucas Cooper bobobo at google.com
Wed Apr 19 17:32:27 EEST 2017


Michael's right. The problem is that NaN is casted to an int, resulting in
rate having undefined value. Not sure how I neglected to add that part.

On 19 Apr. 2017 2:32 am, "Michael Niedermayer" <michael at niedermayer.cc>
wrote:

> On Wed, Apr 19, 2017 at 12:49:38AM +0200, Hendrik Leppkes wrote:
> > On Wed, Apr 19, 2017 at 12:34 AM, Lucas Cooper
> > <bobobo-at-google.com at ffmpeg.org> wrote:
> > > find_fps attempts to infer framerate from AVCodec's timebase. When this
> > > results in a frame rate that isn't explicitly marked as supported in
> > > av_timecode_check_frame_rate, find_fps returns the AVStream's
> > > avg_frame_rate, which, per avformat.h, _may_ be set (or not).
> > >
> > > mov_get_mpeg2_xdcam_codec_tag, mov_get_h264_codec_tag and
> > > find_compressor attempt to call av_q2d on the return value of find_fps,
> > > which in the above case, may result in division by zero.
> >
> > Floating point division by zero is not an error (as av_q2d performs),
> > and in these cases the wrong return value is likely harmless.
> >
> > What is the actual error you are trying to fix?
>
> from looking at the code, i guess its the cast to int of a non finite
> double
>
> [...]
>
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