Merge commit '9469370f'

* commit '9469370f':
  h264: Use AVERROR return codes instead of -1

Only partially merged, as the first hunk is not correct and would result
in endless log spam.
Merged-by: Hendrik Leppkes <h.leppkes@gmail.com>

libavcodec/h264.h

@@ -1191,15 +1191,16 @@ static inline int get_avc_nalsize(H264Context *h, const uint8_t *buf,
 {
     int i, nalsize = 0;
 
-    if (*buf_index >= buf_size - h->nal_length_size)
-        return -1;
+    if (*buf_index >= buf_size - h->nal_length_size) {
+        return AVERROR(EAGAIN);
+    }
 
     for (i = 0; i < h->nal_length_size; i++)
         nalsize = ((unsigned)nalsize << 8) | buf[(*buf_index)++];
     if (nalsize <= 0 || nalsize > buf_size - *buf_index) {
         av_log(h->avctx, AV_LOG_ERROR,
                "AVC: nal size %d\n", nalsize);
-        return -1;
+        return AVERROR_INVALIDDATA;
     }
     return nalsize;
 }