add error messages

Originally committed as revision 5838 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mxf.c

@@ -222,8 +222,10 @@ static int mxf_read_packet(AVFormatContext *s, AVPacket *pkt)
     KLVPacket klv;
 
     while (!url_feof(&s->pb)) {
-        if (klv_read_packet(&klv, &s->pb) < 0)
+        if (klv_read_packet(&klv, &s->pb) < 0) {
+            av_log(s, AV_LOG_ERROR, "error reading KLV packet\n");
             return -1;
+        }
         if (IS_KLV_KEY(klv.key, mxf_essence_element_key)) {
             av_get_packet(&s->pb, pkt, klv.length);
             pkt->stream_index = mxf_get_stream_index(s, &klv);
@@ -822,8 +824,10 @@ static int mxf_read_header(AVFormatContext *s, AVFormatParameters *ap)
 
     mxf->fc = s;
     while (!url_feof(&s->pb)) {
-        if (klv_read_packet(&klv, &s->pb) < 0)
+        if (klv_read_packet(&klv, &s->pb) < 0) {
+            av_log(s, AV_LOG_ERROR, "error reading KLV packet\n");
             return -1;
+        }
         if (IS_KLV_KEY(klv.key, mxf_metadata_track_key))
             ret = mxf_read_metadata_track(mxf, &klv);
         else if (IS_KLV_KEY(klv.key, mxf_metadata_static_track_key))
@@ -856,8 +860,10 @@ static int mxf_read_header(AVFormatContext *s, AVFormatParameters *ap)
             break;
         } else
             url_fskip(&s->pb, klv.length);
-        if (ret < 0)
+        if (ret < 0) {
+            av_log(s, AV_LOG_ERROR, "error reading header metadata\n");
             return ret;
+        }
     }
     return mxf_parse_structural_metadata(mxf);
 }