C/java seem to run it reliably

test.c

#include <stdio.h>

void main(char **argv) {
int a = 0;
 for(a = 0; a < 100; a++) {
   FILE *lsofFile_p = popen("temp\\ffmpeg.exe -list_devices true -f dshow -i dummy 2>&1", "r");

    if (!lsofFile_p)
   {
      printf("bad p");
    return -1;
  }

  int b;
  for(b = 0; b < 20; b++) {
   char buffer[1024];
   char *line_p = fgets(buffer, sizeof(buffer), lsofFile_p);
   printf("got %s", buffer);
   }
   pclose(lsofFile_p);
   printf("done file\n\n\n");
   }

}

test.java

// also appears to run fine

class test {

public static void main(String... args)  throws Exception {

  Process process = Runtime.getRuntime().exec("temp\\ffmpeg.exe -list_devices true -f dshow -i dummy");
  byte[] bytes = new byte[4000];
  process.getErrorStream().read(bytes);
  System.out.println("hellostderr" + new String(bytes));
  bytes = new byte[2000];
  process.getInputStream().read(bytes);
  System.out.println("hellostdout" + new String(bytes));

  process.getErrorStream().read(bytes);
  System.out.println("hellostderr2" + new String(bytes));
  
}
}