2012/1/31 Måns Rullgård <[email protected]>:
> Alex Converse <[email protected]> writes:
>
>> Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
>> ---
>>  libavcodec/ac3dsp.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c
>> index 98c7357..8ff9f7d 100644
>> --- a/libavcodec/ac3dsp.c
>> +++ b/libavcodec/ac3dsp.c
>> @@ -125,7 +125,7 @@ static void ac3_bit_alloc_calc_bap_c(int16_t *mask, 
>> int16_t *psd,
>>              int address = av_clip((psd[bin] - m) >> 5, 0, 63);
>>              bap[bin] = bap_tab[address];
>>          }
>> -    } while (end > ff_ac3_band_start_tab[band++]);
>> +    } while (end > ff_ac3_band_start_tab[++band]);
>>  }
>
> Won't this (untested) do the same thing while simplifying a little:
>
> diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c
> index 98c7357..f97d424 100644
> --- a/libavcodec/ac3dsp.c
> +++ b/libavcodec/ac3dsp.c
> @@ -108,7 +108,7 @@ static void ac3_bit_alloc_calc_bap_c(int16_t *mask, 
> int16_t *psd,
>                                      int snr_offset, int floor,
>                                      const uint8_t *bap_tab, uint8_t *bap)
>  {
> -    int bin, band;
> +    int bin, band, band_end;
>
>     /* special case, if snr offset is -960, set all bap's to zero */
>     if (snr_offset == -960) {
> @@ -120,12 +120,12 @@ static void ac3_bit_alloc_calc_bap_c(int16_t *mask, 
> int16_t *psd,
>     band = ff_ac3_bin_to_band_tab[start];
>     do {
>         int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor;
> -        int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end);
> +        band_end = FFMIN(ff_ac3_band_start_tab[++band], end);
We clip band here
>         for (; bin < band_end; bin++) {
>             int address = av_clip((psd[bin] - m) >> 5, 0, 63);
>             bap[bin] = bap_tab[address];
>         }
> -    } while (end > ff_ac3_band_start_tab[band++]);
> +    } while (end > band_end);
Making this always false
>  }
>

--Alex
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