diff --git a/libmpcodecs/dec_audio.c b/libmpcodecs/dec_audio.c
index 78dddbf05f..cd63b15b25 100644
--- a/libmpcodecs/dec_audio.c
+++ b/libmpcodecs/dec_audio.c
@@ -352,18 +352,10 @@ int init_audio_filters(sh_audio_t *sh_audio, int in_samplerate,
 
 static int filter_n_bytes(sh_audio_t *sh, int len)
 {
-    int error = 0;
-    // Filter
-    af_data_t filter_input = {
-	.audio = sh->a_buffer,
-	.rate = sh->samplerate,
-	.nch = sh->channels,
-	.format = sh->sample_format
-    };
-    af_data_t *filter_output;
-
     assert(len-1 + sh->audio_out_minsize <= sh->a_buffer_size);
 
+    int error = 0;
+
     // Decode more bytes if needed
     while (sh->a_buffer_len < len) {
 	unsigned char *buf = sh->a_buffer + sh->a_buffer_len;
@@ -378,9 +370,16 @@ static int filter_n_bytes(sh_audio_t *sh, int len)
 	sh->a_buffer_len += ret;
     }
 
-    filter_input.len = len;
+    // Filter
+    af_data_t filter_input = {
+	.audio = sh->a_buffer,
+	.len = len,
+	.rate = sh->samplerate,
+	.nch = sh->channels,
+	.format = sh->sample_format
+    };
     af_fix_parameters(&filter_input);
-    filter_output = af_play(sh->afilter, &filter_input);
+    af_data_t *filter_output = af_play(sh->afilter, &filter_input);
     if (!filter_output)
 	return -1;
     if (sh->a_out_buffer_size < sh->a_out_buffer_len + filter_output->len) {