1 files changed, 3 insertions, 1 deletions
diff --git a/libavcodec/h261dec.c b/libavcodec/h261dec.c
index d83fb3114c..88ca63ddc6 100644
--- a/libavcodec/h261dec.c
+++ b/libavcodec/h261dec.c
@@ -581,10 +581,12 @@ static int h261_decode_frame(AVCodecContext *avctx, void *data,
 retry:
     init_get_bits(&s->gb, buf, buf_size * 8);
 
-    if (!s->context_initialized)
+    if (!s->context_initialized) {
         // we need the IDCT permutaton for reading a custom matrix
+        ff_mpv_idct_init(s);
         if (ff_MPV_common_init(s) < 0)
             return -1;
+    }
 
     ret = h261_decode_picture_header(h);