[FFmpeg-devel] [PATCH] avfilter/af_alimiter: fix misbehavior when nb_channels != 2
David Flater
dave at flaterco.com
Wed Aug 24 01:49:29 EEST 2022
This is a friendly reminder.
Cc: Paul B Mahol <onemda at gmail.com>
On 2022-08-14 21:53, David Flater wrote:
> 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 at flaterco.com>
> ---
> libavfilter/af_alimiter.c | 23 +++++++++++++----------
> 1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/libavfilter/af_alimiter.c b/libavfilter/af_alimiter.c
> index 622dc66324..c683c4bcf4 100644
> --- a/libavfilter/af_alimiter.c
> +++ b/libavfilter/af_alimiter.c
> @@ -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;
> }
More information about the ffmpeg-devel
mailing list