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Do not try to read residue if ave_mean <= 1

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Otherwise, we end up with with log(0) or log(1). av_ceil_log2 simply
assumes the argument is non-zero and returns wrong result when it is.
(Not that there is a proper way of returning an undefined value.)
This commit is contained in:
Mashiat Sarker Shakkhar 2012-02-16 02:11:17 +06:00
parent 59df25effd
commit d1ea26f640
1 changed files with 8 additions and 3 deletions
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11
libavcodec/wmalosslessdec.c
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@ -715,9 +715,14 @@ static int decode_channel_residues(WmallDecodeCtx *s, int ch, int tile_size)
quo += get_bits_long(&s->gb, get_bits(&s->gb, 5) + 1);
ave_mean = (s->ave_sum[ch] + (1 << s->movave_scaling)) >> (s->movave_scaling + 1);
rem_bits = av_ceil_log2(ave_mean);
rem = rem_bits ? get_bits(&s->gb, rem_bits) : 0;
residue = (quo << rem_bits) + rem;
if (ave_mean <= 1)
residue = quo;
else
{
rem_bits = av_ceil_log2(ave_mean);
rem = rem_bits ? get_bits(&s->gb, rem_bits) : 0;
residue = (quo << rem_bits) + rem;
}
s->ave_sum[ch] = residue + s->ave_sum[ch] - (s->ave_sum[ch] >> s->movave_scaling);