[linux-audio-dev] maximum ports -problem

[Steve Harris]

On Wed, Jul 13, 2005 at 08:39:53 -0400, Brett McCoy wrote:
> Last night I was setting up a session in Ardour.  I had three tracks for 
> keyboard parts that were from imported audio files, so they did not have 
> any input ports set.  I wanted to bring in drum parts from Hydrogen, and 
> started setting up tracks to correspond with the tracks I was using in 
> Hydrogen.  I got maybe 3 or 4 tracks set up, with the correct inputs, 
> and then suddenly Ardour kept telling me that I was out of jack ports 
> and needed to reset jack.  What is this?  I had used maybe 4 stereo 
> ports total.  My sound card has 12 in/10 out (but I was wasn't using 
> them), and Hydrogen presented 32 stereo tracks via Jack, and I was no 
> where near the limit.  I looked at my jack settings via qjackctl and it 
> was set for 128 ports (assuming this is the same thing).

back of the envelope maths:

soundcard ports are always assigned,
even if theres nothing connected:                   22
hydrogen, 32*2:                                     64
ardour uses something like 4 per mono track,
plus 2 more?                                        34

so thats getting to 120ish, so you could easily have run out.

> After I restarted jackd (and not making any changes in qjackctl), 
> Hydrogen refused to start (it would segfault on startup, but if I 
> started Hydrogen without jackd it would startup fine), and when I 
> reopened the same session in Ardour, the entire screen would freeze 
> (except the mouse).

Thats not good, and I dont know why its doing tht offhand, it could be
because theres some stale files or pipes in your jack tmp directory?

strace-ing or gdb-ing hydrogen might give a clue. 

- Steve