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avfilter/af_alimiter: fix misbehavior when nb_channels != 2 

Some code in alimiter assumes that there are 2 channels, resulting in
clipping if the loudest channel is 3 or above and an out-of-bounds read if
the input is monophonic.  Fix that in 2 places.

Signed-off-by: David Flater <dave@flaterco.com>
This commit is contained in:
David Flater 2022-08-14 21:53:10 -04:00 committed by Paul B Mahol
parent 1adfd28f9e
commit d2b6ec1e27
1 changed files with 13 additions and 10 deletions
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23
libavfilter/af_alimiter.c
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@ -194,10 +194,11 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
} else {
for (i = s->nextiter; i < s->nextiter + s->nextlen; i++) {
int j = i % buffer_size;
double ppeak, pdelta;
double ppeak = 0, pdelta;
ppeak = fabs(buffer[nextpos[j]]) > fabs(buffer[nextpos[j] + 1]) ?
fabs(buffer[nextpos[j]]) : fabs(buffer[nextpos[j] + 1]);
for (c = 0; c < channels; c++) {
ppeak = FFMAX(ppeak, fabs(buffer[nextpos[j] + c]));
}
pdelta = (limit / peak - limit / ppeak) / (((buffer_size - nextpos[j] + s->pos) % buffer_size) / channels);
if (pdelta < nextdelta[j]) {
nextdelta[j] = pdelta;
@ -241,14 +242,16 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
s->delta = get_rdelta(s, release, inlink->sample_rate,
peak, limit, s->att, 1);
if (s->nextlen > 1) {
double ppeak = 0, pdelta;
int pnextpos = nextpos[(s->nextiter + 1) % buffer_size];
double ppeak = fabs(buffer[pnextpos]) > fabs(buffer[pnextpos + 1]) ?
fabs(buffer[pnextpos]) :
fabs(buffer[pnextpos + 1]);
double pdelta = (limit / ppeak - s->att) /
(((buffer_size + pnextpos -
((s->pos + channels) % buffer_size)) %
buffer_size) / channels);
for (c = 0; c < channels; c++) {
ppeak = FFMAX(ppeak, fabs(buffer[pnextpos + c]));
}
pdelta = (limit / ppeak - s->att) /
(((buffer_size + pnextpos -
((s->pos + channels) % buffer_size)) %
buffer_size) / channels);
if (pdelta < s->delta)
s->delta = pdelta;
}