[linux-audio-user] jackd -d alsa -d hw:0 -p512 / problem to start

HI! I was installed alsa + jackd, and jackd not start using this command line: # jackd -d alsa -d hw:0 -p512 And the output is an infinite lines just like the following lines... **** alsa_pcm: xrun of at least 0.019 msecs **** alsa_pcm: xrun of at least 0.051 msecs **** alsa_pcm: xrun of at least 0.016 msecs **** alsa_pcm: xrun of at least 0.015 msecs **** alsa_pcm: xrun of at least 0.020 msecs **** alsa_pcm: xrun of at least 0.014 msecs **** alsa_pcm: xrun of at least 0.025 msecs [...] But jackd is 'running' but not usable, because 'ardour' abort saying: 'jackd not present' What can I do? thanks a lot for your help, Felix