Moved from freebsd-chat:
Quick addition: Had a look through the questions archive, nothing jumped out and answered this, but it's possible I missed something.
I'm currently in the middle of writing an automated radio playout system for a northern student radio station in the UK (post SBN liquidation).
I have the requirement of it running on a *nix system. I'm a large BSD advocate between our friends, so would prefer not to use Linux.
The system design consists of a daemon for each soundcard used in the studio. I'm currently in the process of writing this daemon.
I've found that there is about a 800ms delay between the output data being written to /dev/dsp and being able to hear the output from the soundcard on FreeBSD. I'm working to a 200ms deadline.
I'm opening the soundcard with:
audio_fd = open((char *) device, O_WRONLY | O_FSYNC | O_DIRECT);
I've used O_DIRECT and O_FSYNC to try and get rid of this delay, but alas that didn't work, device is cast as it's coming from a void * (thanks to pthread_create ;).
The daemon outputs blocks of 0 when there is no actual audio to output so the sound card is always fed.
While this isn't a problem for mpg123, it is for this application. I've tried to find where the delay is, however I haven't had any luck.
Could anyone knowledgable let me know if there's any hope for getting rid of it (hacking the kernel is fine ;) or if I should "give up" and go to linux?
I suppose Linux does have ALSA which claims 2.6ms latency but I was hoping to just use OSS. Oh well.
For reference the test machine is a 2.2Ghz machine with a AC97 chip (yeah crap I know, studio playout machines will probably have a Creative card) running 4.10-STABLE (Yeasturday's cvsup).
My appologies if this isn't the right place, I'm happy to go pester else where. Heh.
Pete. -- Peter Wood BSc (Hons) :: <[EMAIL PROTECTED]> :: Tel +44 7974 799440
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