h264: Fix decoding delay for Intra only streams

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/h264_ps.c

@@ -530,7 +530,8 @@ int ff_h264_decode_seq_parameter_set(GetBitContext *gb, AVCodecContext *avctx,
 
     /* if the maximum delay is not stored in the SPS, derive it based on the
      * level */
-    if (!sps->bitstream_restriction_flag) {
+    if (!sps->bitstream_restriction_flag &&
+        (sps->ref_frame_count || avctx->strict_std_compliance >= FF_COMPLIANCE_STRICT)) {
         sps->num_reorder_frames = MAX_DELAYED_PIC_COUNT - 1;
         for (i = 0; i < FF_ARRAY_ELEMS(level_max_dpb_mbs); i++) {
             if (level_max_dpb_mbs[i][0] == sps->level_idc) {