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dartffmpegstdoutstderr

FFmpeg no output on stdout

The problem is simple:

When I run for example:

print(Process.runSync('ipconfig', []).stdout)

I get the expected output:


Windows IP Configuration


Unknown adapter Helyi kapcsolat:

   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
......

But when I try to run ffmpeg, I get no output:

print(Process.runSync('ffmpeg', []).stdout)

What I'd expect in this case is to get the help output from ffmpeg.

My guess is, ffmpeg has some kind of "different" way of interacting with stdout than most executables. What could be the problem? I'm totally lost here.

I need to read the stdout eventually to get the output of ffmpeg -list_devices true -f dshow -i dummy, which would list the available DirectShow devices.

Solution

  • FFmpeg outputs useful data to stderr, including the help output and the device list of my original command, ffmpeg -list_devices true -f dshow -i dummy.

    Simply use stderr (as well as stdout) to get the output:

    print(Process.runSync('ffmpeg', []).stderr)