avcodec/mpeg4videodec: Use more specific error codes

Forward error codes where possible.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mpeg4video.h

@@ -239,12 +239,12 @@ static inline int ff_mpeg4_pred_dc(MpegEncContext *s, int n, int level,
             if (level < 0) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "dc<0 at %dx%d\n", s->mb_x, s->mb_y);
-                return -1;
+                return AVERROR_INVALIDDATA;
             }
             if (level > 2048 + scale) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "dc overflow at %dx%d\n", s->mb_x, s->mb_y);
-                return -1;
+                return AVERROR_INVALIDDATA;
             }
         }
         if (level < 0)