lavf/tcp: Clarify that the -timeout option takes microseconds.

libavformat/tcp.c

@@ -45,7 +45,7 @@ typedef struct TCPContext {
 #define E AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {
     { "listen",          "Listen for incoming connections",  OFFSET(listen),         AV_OPT_TYPE_INT, { .i64 = 0 },     0,       1,       .flags = D|E },
-    { "timeout",     "set timeout of socket I/O operations", OFFSET(rw_timeout),     AV_OPT_TYPE_INT, { .i64 = -1 },         -1, INT_MAX, .flags = D|E },
+    { "timeout",     "set timeout (in microseconds) of socket I/O operations", OFFSET(rw_timeout),     AV_OPT_TYPE_INT, { .i64 = -1 },         -1, INT_MAX, .flags = D|E },
     { "listen_timeout",  "Connection awaiting timeout",      OFFSET(listen_timeout), AV_OPT_TYPE_INT, { .i64 = -1 },         -1, INT_MAX, .flags = D|E },
     { NULL }
 };