clarify why the encoder is failing

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@20556 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/dnxhdenc.c

@@ -783,7 +783,8 @@ static int dnxhd_encode_picture(AVCodecContext *avctx, unsigned char *buf, int b
     else
         ret = dnxhd_encode_fast(avctx, ctx);
     if (ret < 0) {
-        av_log(avctx, AV_LOG_ERROR, "picture could not fit ratecontrol constraints\n");
+        av_log(avctx, AV_LOG_ERROR,
+               "picture could not fit ratecontrol constraints, increase qmax\n");
         return -1;
     }