On Friday 19 June 2009, Xiaofan Chen wrote: > On Fri, Jun 19, 2009 at 8:20 PM, David Brownell<david-b@xxxxxxxxxxx> wrote: > > On Tuesday 16 June 2009, Laurent Pinchart wrote: > >> > We don't need to let gadget device user space application do the > >> > conversion. > >> > >> I'm afraid that won't work. The host and device clocks are not synchronized, > >> so you'll experience buffer underruns or overruns. > > > > Maybe someone is going to finally get into how to do synchronization > > with ISO streams in Linux? Read the USB spec, there are several > > mechanisms. I believe there are likely to be some missing lowlevel > > primitives in the kernel-to-kernel interfaces, needed to make those > > things work right. > > > > Though I think you're talking about a different issue, a bit higher > > up in the stack. There might be missing features there too. ;) > > Are you thinking of Async type of synchronisation by feedback > endpoint? At the low level, yes that's one of the options. The "strongest" of them, in fact. Last I looked, I concluded the Linux-USB audio doesn't actually try to use any of those schemes. > Very few USB audio device supports this. And it > seems not many people in the whole word understand this > (for one I do not). It is said this it the best to counter clock jitter. > http://www.audioasylum.com/forums/pcaudio/messages/7719.html > > According to sc6po (who has done one device), it works better > in Linux than Windows XP. He says that his device works great > under Linux but can crash XP from time to time. > http://www.microchip.com/forums/tm.aspx?m=344751 > http://www.microchip.com/forums/tm.aspx?m=270049&mpage=7 (post 136) > > But Vista seems to catch up. > http://www.microchip.com/forums/tm.aspx?m=424170 You again are providing a fountain of relevant information! :) -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
