avcodec/h264: Use named identifier for single thread fall-back return from ff_h264_decode_slice_header()

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

libavcodec/h264.c

@@ -1727,7 +1727,7 @@ again:
                 if (err < 0)
                     av_log(h->avctx, AV_LOG_ERROR, "decode_slice_header error\n");
                 h->ref_count[0] = h->ref_count[1] = h->list_count = 0;
-            } else if (err == 1) {
+            } else if (err == SLICE_SINGLETHREAD) {
                 /* Slice could not be decoded in parallel mode, copy down
                  * NAL unit stuff to context 0 and restart. Note that
                  * rbsp_buffer is not transferred, but since we no longer

libavcodec/h264.h

@@ -1098,6 +1098,7 @@ int ff_pred_weight_table(H264Context *h);
 int ff_set_ref_count(H264Context *h);
 
 int ff_h264_decode_slice_header(H264Context *h, H264Context *h0);
+#define SLICE_SINGLETHREAD 1
 #define SLICE_SKIPED 2
 
 int ff_h264_execute_decode_slices(H264Context *h, unsigned context_count);

libavcodec/h264_slice.c

@@ -1890,7 +1890,7 @@ int ff_h264_decode_slice_header(H264Context *h, H264Context *h0)
             if (h != h0) {
                 av_log(h->avctx, AV_LOG_ERROR,
                        "Deblocking switched inside frame.\n");
-                return 1;
+                return SLICE_SINGLETHREAD;
             }
         }
     }