On Thu, Apr 16, 2015 at 1:00 PM, Andreas Cadhalpun
<andreas.cadhal...@googlemail.com> wrote:
> If both band->active_lines and band->thr are 0.0f, the division is
> undefined, making norm_fac not a number.
>
> NaN is passed on to other variables until it finally reaches
> sce->sf_idx and is converted to an integer (-2147483648).
>
> This causes a segmentation fault when it is used as array index.
>
> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
> ---
> libavcodec/aacpsy.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c
> index d1e65f6..b71933b 100644
> --- a/libavcodec/aacpsy.c
> +++ b/libavcodec/aacpsy.c
> @@ -727,7 +727,10 @@ static void psy_3gpp_analyze_channel(FFPsyContext *ctx,
> int channel,
> if (active_lines > 0.0f)
> band->thr = calc_reduced_thr_3gpp(band,
> coeffs[g].min_snr, reduction);
> pe += calc_pe_3gpp(band);
> - band->norm_fac = band->active_lines / band->thr;
> + if (band->active_lines != 0.0f)
> + band->norm_fac = band->active_lines / band->thr;
> + else
> + band->norm_fac = 0.0f;
> norm_fac += band->norm_fac;
> }
> }
It should be if band->thr > 0.0f, all divisions by zero return
something that casts into an ~1:
Try:
#include "stdio.h"
int main() {
printf("%d\n", int(0.0f / 0.0f));
printf("%d\n", int(1.0f / 0.0f));
return 0;
}
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