Hi, tisdagen den 09 december 2003 12.22 skrev Steve Harris: > On Tue, Dec 09, 2003 at 09:25:42AM +0100, Clemens Ladisch wrote: > > > > I seem to recall that it does, but that the packet size is smaller, > > > > making the latency problem easier to deal with. > > > > > > Isoch - 1394 has a timer operating on the bus. This timer happens > > > (roughly) every 125uS. > > > > USB isochronous transfers happen once per millisecond. > > OK, so its the difference between 44 or 45 samples per packet at 44.1kHz > (USB) and 5 or 6 (1394). > > So, a plausible jack period of 64 samples will be 11 or 12 1395 packets, > but always 125uS of jitter of course, (10 or 11 packets at 48k). > > I dont really have any idea how bad that is, its 8% of the availble time > slot for processing the 64 samples. > > You could lessen the effect of the jitter by having triple-buffering in > software, as in a 3x64 PCI soundcard - I dont know wether thats better > than just going to 128 samples or not. > > FWIW, for my needs I rarely go below 256 samples/period anyway, even > though my setup is capable of it, but I understand there are people who > really need very low latency. > > At 256 samples/period the jitter is only 2.1% of the time slice, which is > unlilkly to matter - cache temperature and so on has a far greater effect > than that. Though it is interesting debating the technical merits of firewire, for me, atleast, it would be far more interesting to get it actually working. I'm _very_ interested in utilizing these hardwares. I googled a little last night, some people we all know popped up here and there (Hi Steve, Mark and Bob). There was a LAD message from 2001, someone who had been in contact with Yamaha and it seemed they(Yamaha) where working towards making mLan a part of the A&M standard (I think I got that right...not sure)... now... I'm not entirely sure what this means. It seemed as the A&M standards also cost a lot of money? Do we have enough information to implement mLan support? As I understand it, Bob Ham had/is working on implementing 61883 support for Jack, which seems like it's needed for mLan, a layer below it perhaps? How far has this come, is there something one can test somehow, what hardware do one need? Regards, Robert ps. I'm cc:ing LAD as I'd like to move the discussion there. Remove LAU if you respond to this. ds.
