[FFmpeg-devel] Patch proposal : Fix crash with astats filter when no audio input

[Martin Vignali]

In attach a sample file, who make a crash. (on mac os x with latest git
version, and on windows with older version).

i just make the test now, and s->nb_channels can be 0. (this is the case
with the file in attach).

For the coding style.
Do you prefer something like that : ?
if (s->nb_channels == 0) || (nb_samples !=0)
    return;

Best regards

Martin

2015-03-08 0:07 GMT+01:00 Nicolas George <george at nsup.org>:

> Le septidi 17 ventôse, an CCXXIII, Martin Vignali a écrit :
> > Exemple to create the crash :
> > ffmpeg -i fileWithoutSound -filter astats -f null -
>
> I experience no crash. As far as I can see, the divisions happen with
> floats, which is valid.
>
> > From 621b18a278c3d314da773b8eec9f9e12707a20bb Mon Sep 17 00:00:00 2001
> > From: Martin Vignali <martin.vignali at gmail.com>
> > Date: Sat, 7 Mar 2015 23:09:40 +0100
> > Subject: [PATCH] Fix crash in astats filter, whith no audio input
> >
> > Avoid Zero division in print part.
> > ---
> >  libavfilter/af_astats.c | 24 +++++++++++++-----------
> >  1 file changed, 13 insertions(+), 11 deletions(-)
> >
> > diff --git a/libavfilter/af_astats.c b/libavfilter/af_astats.c
> > index 60ccd73..8e90f6b 100644
> > --- a/libavfilter/af_astats.c
> > +++ b/libavfilter/af_astats.c
> > @@ -222,18 +222,20 @@ static void print_stats(AVFilterContext *ctx)
> >          av_log(ctx, AV_LOG_INFO, "Peak count: %"PRId64"\n",
> p->min_count + p->max_count);
> >      }
> >
> > -    av_log(ctx, AV_LOG_INFO, "Overall\n");
> > -    av_log(ctx, AV_LOG_INFO, "DC offset: %f\n", max_sigma_x /
> (nb_samples / s->nb_channels));
> > -    av_log(ctx, AV_LOG_INFO, "Min level: %f\n", min);
> > -    av_log(ctx, AV_LOG_INFO, "Max level: %f\n", max);
> > -    av_log(ctx, AV_LOG_INFO, "Peak level dB: %f\n",
> LINEAR_TO_DB(FFMAX(-min, max)));
> > -    av_log(ctx, AV_LOG_INFO, "RMS level dB: %f\n",
> LINEAR_TO_DB(sqrt(sigma_x2 / nb_samples)));
> > -    av_log(ctx, AV_LOG_INFO, "RMS peak dB: %f\n",
> LINEAR_TO_DB(sqrt(max_sigma_x2)));
>
> Please do the reindent in a separate patch.
>
> > -    if (min_sigma_x2 != 1)
>
> > +    if ((s->nb_channels != 0)&&(nb_samples !=0)){/* Avoid crash when
> input don't have sound */
>
> s->nb_channels can not be 0.
>
> And cosmetic nit: the standard coding style in FFmpeg is: no "!= 0", no
> extra parentheses on tests, spaces around operators, including &&, and
> between clause and braces.
>
> > +        av_log(ctx, AV_LOG_INFO, "Overall\n");
> > +        av_log(ctx, AV_LOG_INFO, "DC offset: %f\n", max_sigma_x /
> (nb_samples / s->nb_channels));
> > +        av_log(ctx, AV_LOG_INFO, "Min level: %f\n", min);
> > +        av_log(ctx, AV_LOG_INFO, "Max level: %f\n", max);
> > +        av_log(ctx, AV_LOG_INFO, "Peak level dB: %f\n",
> LINEAR_TO_DB(FFMAX(-min, max)));
> > +        av_log(ctx, AV_LOG_INFO, "RMS level dB: %f\n",
> LINEAR_TO_DB(sqrt(sigma_x2 / nb_samples)));
> > +        av_log(ctx, AV_LOG_INFO, "RMS peak dB: %f\n",
> LINEAR_TO_DB(sqrt(max_sigma_x2)));
> > +        if (min_sigma_x2 != 1)
> >          av_log(ctx, AV_LOG_INFO, "RMS trough dB: %f\n",
> LINEAR_TO_DB(sqrt(min_sigma_x2)));
> > -    av_log(ctx, AV_LOG_INFO, "Flat factor: %f\n",
> LINEAR_TO_DB((min_runs + max_runs) / (min_count + max_count)));
> > -    av_log(ctx, AV_LOG_INFO, "Peak count: %f\n", (min_count +
> max_count) / (double)s->nb_channels);
> > -    av_log(ctx, AV_LOG_INFO, "Number of samples: %"PRId64"\n",
> nb_samples / s->nb_channels);
> > +        av_log(ctx, AV_LOG_INFO, "Flat factor: %f\n",
> LINEAR_TO_DB((min_runs + max_runs) / (min_count + max_count)));
> > +        av_log(ctx, AV_LOG_INFO, "Peak count: %f\n", (min_count +
> max_count) / (double)s->nb_channels);
> > +        av_log(ctx, AV_LOG_INFO, "Number of samples: %"PRId64"\n",
> nb_samples / s->nb_channels);
> > +    }
> >  }
> >
> >  static av_cold void uninit(AVFilterContext *ctx)
>
> Regards,
>
> --
>   Nicolas George
>
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> ffmpeg-devel at ffmpeg.org
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>
>
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