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ac3dec: detect out-of-range exponents 

Originally committed as revision 16015 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-12-06 15:36:23 +00:00
parent d8b66635e0
commit ce7d842fa6
1 changed files with 10 additions and 4 deletions
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14
libavcodec/ac3dec.c
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@ -372,7 +372,7 @@ static void set_downmix_coeffs(AC3DecodeContext *s)
* Decode the grouped exponents according to exponent strategy.
* reference: Section 7.1.3 Exponent Decoding
*/
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
static int decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
uint8_t absexp, int8_t *dexps)
{
int i, j, grp, group_size;
@ -391,11 +391,14 @@ static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
/* convert to absolute exps and expand groups */
prevexp = absexp;
for(i=0; i<ngrps*3; i++) {
prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
prevexp += dexp[i] - 2;
if (prevexp < 0 || prevexp > 24)
return -1;
for(j=0; j<group_size; j++) {
dexps[(i*group_size)+j] = prevexp;
}
}
return 0;
}
/**
@ -989,9 +992,12 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
for (ch = !cpl_in_use; ch <= s->channels; ch++) {
if (s->exp_strategy[blk][ch] != EXP_REUSE) {
s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
decode_exponents(gbc, s->exp_strategy[blk][ch],
if (decode_exponents(gbc, s->exp_strategy[blk][ch],
s->num_exp_groups[ch], s->dexps[ch][0],
&s->dexps[ch][s->start_freq[ch]+!!ch]);
&s->dexps[ch][s->start_freq[ch]+!!ch])) {
av_log(s->avctx, AV_LOG_ERROR, "exponent out-of-range\n");
return -1;
}
if(ch != CPL_CH && ch != s->lfe_ch)
skip_bits(gbc, 2); /* skip gainrng */
}