@@ -95,6 +95,12 @@ static av_cold int init(AVFilterContext *ctx, const char *args0, void *opaque)

     int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels

     double gain;

+    if (!args0) {

+        av_log(ctx, AV_LOG_ERROR,

+               "pan filter needs a channel layout and a set "

+               "of channels definitions as parameter\n");

+        return AVERROR(EINVAL);

+    }

     if (!args)

         return AVERROR(ENOMEM);

     arg = av_strtok(args, ":", &tokenizer);