avconv: fix the muxrate values for -target

The mpegenc private option values are in 50-byte units.

CC: libav-stable@libav.org

avconv_opt.c

@@ -1803,7 +1803,7 @@ static int opt_target(void *optctx, const char *opt, const char *arg)
         parse_option(o, "ac", "2", options);
 
         opt_default(NULL, "packetsize", "2324");
-        opt_default(NULL, "muxrate", "1411200"); // 2352 * 75 * 8;
+        opt_default(NULL, "muxrate", "3528"); // 2352 * 75 / 50;
 
         /* We have to offset the PTS, so that it is consistent with the SCR.
            SCR starts at 36000, but the first two packs contain only padding
@@ -1849,7 +1849,7 @@ static int opt_target(void *optctx, const char *opt, const char *arg)
         opt_default(NULL, "bufsize", "1835008"); // 224*1024*8;
 
         opt_default(NULL, "packetsize", "2048");  // from www.mpucoder.com: DVD sectors contain 2048 bytes of data, this is also the size of one pack.
-        opt_default(NULL, "muxrate", "10080000"); // from mplex project: data_rate = 1260000. mux_rate = data_rate * 8
+        opt_default(NULL, "muxrate", "25200"); // from mplex project: data_rate = 1260000. mux_rate = data_rate / 50
 
         opt_default(NULL, "b:a", "448000");
         parse_option(o, "ar", "48000", options);