return an error if we can not get a full packet,

fixes hang on EOF

Originally committed as revision 16740 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/iss.c

@@ -112,8 +112,8 @@ static int iss_read_packet(AVFormatContext *s, AVPacket *pkt)
     IssDemuxContext *iss = s->priv_data;
     int ret = av_get_packet(s->pb, pkt, iss->packet_size);
 
-    if(ret < 0)
-        return ret;
+    if(ret != iss->packet_size)
+        return AVERROR(EIO);
 
     pkt->stream_index = 0;
     pkt->pts = url_ftell(s->pb) - iss->sample_start_pos;