On Thu, Nov 3, 2011 at 4:10 PM, Ronald S. Bultje <[email protected]> wrote:
> Hi,
>
> On Thu, Nov 3, 2011 at 4:03 PM, Alex Converse <[email protected]> wrote:
>> ---
>> libavcodec/vp6.c | 6 ++++--
>> 1 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/vp6.c b/libavcodec/vp6.c
>> index e29f901..698b396 100644
>> --- a/libavcodec/vp6.c
>> +++ b/libavcodec/vp6.c
>> @@ -413,8 +413,10 @@ static void vp6_parse_coeff_huffman(VP56Context *s)
>> }
>> }
>> coeff_idx+=run;
>> - cg = FFMIN(vp6_coeff_groups[coeff_idx], 3);
>> - vlc_coeff = &s->ract_vlc[pt][ct][cg];
>> + if (coeff_idx < 64) {
>> + cg = FFMIN(vp6_coeff_groups[coeff_idx], 3);
>> + vlc_coeff = &s->ract_vlc[pt][ct][cg];
>> + }
>
> Do you want to return an error? I.e. else return -1 or so, perhaps
> under error_resilience>=EXPLODE? Or is this something that happens in
> regular streams?
>
This seems to happen in 'normal' streams for the last element. A
little more context shows that the loop breaks immediately afterward.
for (coeff_idx=0; coeff_idx<64; ) {
int run = 1;
if (coeff_idx<2 && s->nb_null[coeff_idx][pt]) {
s->nb_null[coeff_idx][pt]--;
if (coeff_idx)
break;
} else {
if (get_bits_count(&s->gb) >= s->gb.size_in_bits)
return;
coeff = get_vlc2(&s->gb, vlc_coeff->table, 9, 3);
if (coeff == 0) {
if (coeff_idx) {
int pt = (coeff_idx >= 6);
run += get_vlc2(&s->gb, s->runv_vlc[pt].table, 9, 3);
if (run >= 9)
run += get_bits(&s->gb, 6);
} else
s->nb_null[0][pt] = vp6_get_nb_null(s);
ct = 0;
} else if (coeff == 11) { /* end of block */
if (coeff_idx == 1) /* first AC coeff ? */
s->nb_null[1][pt] = vp6_get_nb_null(s);
break;
} else {
int coeff2 = vp56_coeff_bias[coeff];
if (coeff > 4)
coeff2 += get_bits(&s->gb, coeff <= 9 ? coeff - 4 : 11);
ct = 1 + (coeff2 > 1);
sign = get_bits1(&s->gb);
coeff2 = (coeff2 ^ -sign) + sign;
if (coeff_idx)
coeff2 *= s->dequant_ac;
idx = model->coeff_index_to_pos[coeff_idx];
s->block_coeff[b][permute[idx]] = coeff2;
}
}
coeff_idx+=run;
if (coeff_idx < 64) {
cg = FFMIN(vp6_coeff_groups[coeff_idx], 3);
vlc_coeff = &s->ract_vlc[pt][ct][cg];
}
}
--Alex
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