[FFmpeg-user] can not set the defaut stream!

[刘宏川]

if FFmeg.exe's output has more than one stream of the same kind, such as audo or subtitle,  there is not  the default one. 
Especially‍ if there is no the default subtitle, most of the players will not display any subtitle. FFproble.exe can show if there is the deflaut stream of every stream.
FFprobe   -show_streams INPUT
 
[STREAM]
...
DISPOSITION:default=0
...
[/STREAM]