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-rw-r--r--libavfilter/af_pan.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/libavfilter/af_pan.c b/libavfilter/af_pan.c
index fbd79a5a42..94f15876f5 100644
--- a/libavfilter/af_pan.c
+++ b/libavfilter/af_pan.c
@@ -102,7 +102,7 @@ static av_cold int init(AVFilterContext *ctx)
{
PanContext *const pan = ctx->priv;
char *arg, *arg0, *tokenizer, *args = av_strdup(pan->args);
- int out_ch_id, in_ch_id, len, named, ret;
+ int out_ch_id, in_ch_id, len, named, ret, sign = 1;
int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels
double gain;
@@ -178,14 +178,18 @@ static av_cold int init(AVFilterContext *ctx)
ret = AVERROR(EINVAL);
goto fail;
}
- pan->gain[out_ch_id][in_ch_id] = gain;
+ pan->gain[out_ch_id][in_ch_id] = sign * gain;
skip_spaces(&arg);
if (!*arg)
break;
- if (*arg != '+') {
+ if (*arg == '-') {
+ sign = -1;
+ } else if (*arg != '+') {
av_log(ctx, AV_LOG_ERROR, "Syntax error near \"%.8s\"\n", arg);
ret = AVERROR(EINVAL);
goto fail;
+ } else {
+ sign = 1;
}
arg++;
}