[LAD] handling data streams: file vs callback

Dave Robillard drobilla at connect.carleton.ca
Mon Aug 6 23:25:15 UTC 2007

On Sun, 2007-08-05 at 17:12 +0700, Patrick Shirkey wrote:
> Dirk Jagdmann wrote:
> > Hello Patrick,
> > 
> >> I'm trying to jackify xwax. Xwax is a linux based emulator for Rane 
> >> serato and Final scratch.
> >> I have successfully adapted the code from jackEQ to allow xwax to 
> >> register and connect several JACK i/o's.
> >> However the original system uses file descriptors for handling the 
> >> data (oss/alsa) internally and this is not instantly compatible with 
> >> the JACK callback system. At least it's not obvious to me how to link the 
> > 
> > I don't know xwax, but since it currently has oss and alsa output I 
> > guess it is using a "blocking IO" model instead of the "callback" model 
> > of jack. Restructuring the logic from blocking to callbacks can be 
> > complicated. I you want to have a first result have a look at
> > http://bio2jack.sourceforge.net/ which should fill your gap.
> > 
> Hi,
> Thanks for your suggestion. However I want to get multiple i/o's working 
> natively.
> I'm fairly certain the code doesn't need restructuring. It's more a case 
> of how to  connect the internal data stream which is read from disk to 
> jack outputs or jack inputs to the internal stream.

Read from the disk to a ringbuffer (Jack includes one) in some thread
other than the Jack thread, then in the process callback (Jack thread)
read from that ringbuffer and write it to the port buffers.



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