mpegvideo: replace assert about interlaced EC with debug av_log()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo.c

@@ -370,7 +370,9 @@ static void mpeg_er_decode_mb(void *opaque, int ref, int mv_dir, int mv_type,
     s->dest[1] = s->current_picture.f->data[1] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);
     s->dest[2] = s->current_picture.f->data[2] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);
 
-    assert(ref == 0);
+    if (ref)
+        av_log(s->avctx, AV_LOG_DEBUG,
+               "Interlaced error concealment is not fully implemented\n");
     ff_mpv_decode_mb(s, s->block);
 }